Audio frequency range, equalizer. Features of human sound perception
Below 20 Hz and above 20 kHz there are, respectively, areas of infra- and ultrasound inaudible to humans. The curves located between the pain threshold curve and the hearing threshold curve are called equal loudness curves and reflect the difference in human perception of sound at different frequencies.
Since sound waves are an oscillatory process, the sound intensity and sound pressure at a point in the sound field change in time according to a sinusoidal law. Characteristic quantities are their root-mean-square values. The dependence of the root-mean-square values of the sinusoidal noise components or their corresponding levels in decibels on frequency is called the frequency spectrum of noise (or simply spectrum). Spectra are obtained using a set of electrical filters that pass the signal in a certain frequency band - bandwidth.
To obtain the frequency characteristics of noise, the audio frequency range is divided into bands with a certain ratio of boundary frequencies (Fig. 2)
Octave band - frequency band in which the upper limit frequency f V equal to twice the lower frequency f n , i.e. f V/ f n = 2. For example, if we take a musical scale, then a sound with a frequency of f = 262 Hz is “do” of the first octave. Sound from f= 262 x 2 = 524 Hz - “up to” the second octave. “A” of the first octave is 440 Hz, “A” of the second is 880 Hz. Most often, the sound range is divided into octaves, or octave bands. The octave band is characterized by the geometric mean frequencyfthis year = fn fV
In some cases (detailed study of noise sources, sound insulation efficiency), division into half-octave bands is used (fв/fн = 
) and third-octave bands (fв/fн = 
=
1,26).
3. Measurement of industrial noise
Sound is characterized by its intensity 
and sound pressure R
Pa. In addition, any noise source is characterized by sound power, which is the total amount of sound energy emitted by the noise source into the surrounding space.
Taking into account the logarithmic dependence of sensation on changes in the energy of the stimulus (Weber-Fechner law) and the expediency of unifying units and the convenience of operating with numbers, it is customary to use not the values of intensity, sound pressure and power themselves, but their logarithmic levels
L J = 10 lg ,
Where I– sound intensity at a given point, I 0 – sound intensity corresponding to the hearing threshold equal to 10 -12 W/m, R– sound pressure at a given point in space, R 0 – threshold sound pressure equal to 210 -5 Pa, F– sound power at a given point, F 0 - threshold sound power equal to 10 -12 W.
At normal atmospheric pressure
L J = L p = L
Sound pressure level is used to measure noise to assess its impact on humans. L p(often denoted simply L). Intensity level L J used in acoustic calculations of premises.
About the section
This section contains articles devoted to phenomena or versions that in one way or another may be interesting or useful to researchers of the unexplained.
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Peculiarities of human perception. Hearing
Sound is vibrations, i.e. periodic mechanical disturbance in elastic media - gaseous, liquid and solid. Such a disturbance, which represents some physical change in the medium (for example, a change in density or pressure, displacement of particles), propagates in it in the form of a sound wave. A sound may be inaudible if its frequency is beyond the sensitivity of the human ear, or if it travels through a medium, such as a solid, that cannot have direct contact with the ear, or if its energy is rapidly dissipated in the medium. Thus, the process of perceiving sound that is usual for us is only one side of acoustics.
Sound waves
Sound wave
Sound waves can serve as an example of an oscillatory process. Any oscillation is associated with a violation of the equilibrium state of the system and is expressed in the deviation of its characteristics from equilibrium values with a subsequent return to the original value. For sound vibrations, this characteristic is the pressure at a point in the medium, and its deviation is the sound pressure.
Consider a long pipe filled with air. A piston that fits tightly to the walls is inserted into it at the left end. If the piston is sharply moved to the right and stopped, the air in the immediate vicinity of it will be compressed for a moment. Then compressed air will expand, pushing the air adjacent to it to the right, and the region of compression, originally created near the piston, will move along the pipe at a constant speed. This compression wave is the sound wave in the gas.
That is, a sharp displacement of particles of an elastic medium in one place will increase the pressure in this place. Thanks to the elastic bonds of particles, pressure is transmitted to neighboring particles, which, in turn, act on the next ones, and the area high blood pressure as if moving in an elastic medium. A region of high pressure is followed by a region of low pressure, and thus a series of alternating regions of compression and rarefaction are formed, propagating in the medium in the form of a wave. Each particle of the elastic medium in this case will perform oscillatory movements.
A sound wave in a gas is characterized by excess pressure, excess density, displacement of particles and their speed. For sound waves, these deviations from equilibrium values are always small. Thus, the excess pressure associated with the wave is much less than the static pressure of the gas. Otherwise, we are dealing with another phenomenon - a shock wave. In a sound wave corresponding to normal speech, the excess pressure is only about one millionth of atmospheric pressure.
The important fact is that the substance is not carried away by the sound wave. A wave is only a temporary disturbance passing through the air, after which the air returns to an equilibrium state.
Wave motion, of course, is not unique to sound: light and radio signals travel in the form of waves, and everyone is familiar with waves on the surface of water.
Thus, sound, in a broad sense, is elastic waves propagating in some elastic medium and creating mechanical vibrations in it; in a narrow sense, the subjective perception of these vibrations by the special sense organs of animals or humans.
Like any wave, sound is characterized by amplitude and frequency spectrum. Typically, a person hears sounds transmitted through the air in the frequency range from 16-20 Hz to 15-20 kHz. Sound below the range of human audibility is called infrasound; higher: up to 1 GHz, - ultrasound, from 1 GHz - hypersound. Among the audible sounds, phonetic, speech sounds and phonemes (which make up spoken language) and musical sounds (which make up music).
Longitudinal and transverse sound waves are distinguished depending on the ratio of the direction of propagation of the wave and the direction of mechanical vibrations of the particles of the propagation medium.
In liquid and gaseous media, where there are no significant fluctuations in density, acoustic waves are longitudinal in nature, that is, the direction of vibration of the particles coincides with the direction of movement of the wave. In solids, in addition to longitudinal deformations, elastic shear deformations also occur, causing the excitation of transverse (shear) waves; in this case, the particles oscillate perpendicular to the direction of wave propagation. The speed of propagation of longitudinal waves is much greater than the speed of propagation of shear waves.
The air is not uniform for sound everywhere. It is known that air is constantly in motion. The speed of its movement in different layers is not the same. In layers close to the ground, the air comes into contact with its surface, buildings, forests, and therefore its speed here is less than at the top. Due to this, the sound wave does not travel equally fast at the top and bottom. If the movement of air, i.e., the wind, is a companion to sound, then in the upper layers of the air the wind will drive the sound wave more strongly than in the lower layers. When there is a headwind, sound at the top travels slower than at the bottom. This difference in speed affects the shape of the sound wave. As a result of wave distortion, sound does not travel straight. With a tailwind, the line of propagation of the sound wave bends downward, and with a headwind, it bends upward.
Another reason for the uneven propagation of sound in the air. This is the different temperature of its individual layers.
Unevenly heated layers of air, like the wind, change the direction of sound. During the day, the sound wave bends upward because the speed of sound in the lower, hotter layers is greater than in the upper layers. In the evening, when the earth, and with it the nearby layers of air, quickly cool, the upper layers become warmer than the lower ones, the speed of sound in them is greater, and the line of propagation of sound waves bends downward. Therefore, in the evenings, out of the blue, you can hear better.
When observing clouds, you can often notice how at different altitudes they move not only at different speeds, but sometimes in different directions. This means that the wind at different heights from the ground may have different speeds and directions. The shape of the sound wave in such layers will also vary from layer to layer. Let, for example, the sound come against the wind. In this case, the sound propagation line should bend and go upward. But if a layer of slow-moving air gets in its way, it will change its direction again and may return to the ground again. It is then that in the space from the place where the wave rises in height to the place where it returns to the ground, a “zone of silence” appears.
Organs of sound perception
Hearing - ability biological organisms perceive sounds with the hearing organs; a special function of the hearing aid, excited by sound vibrations in the environment, such as air or water. One of the biological five senses, also called acoustic perception.
The human ear perceives sound waves with a length of approximately 20 m to 1.6 cm, which corresponds to 16 - 20,000 Hz (oscillations per second) when vibrations are transmitted through the air, and up to 220 kHz when sound is transmitted through the bones of the skull. These waves have important biological significance, for example, sound waves in the range of 300-4000 Hz correspond to the human voice. Sounds above 20,000 Hz have little practical significance, as they slow down quickly; vibrations below 60 Hz are perceived through the vibration sense. The range of frequencies that a person is able to hear is called the auditory or sound range; higher frequencies are called ultrasound, and lower frequencies are called infrasound.
The ability to distinguish sound frequencies greatly depends on the individual: his age, gender, susceptibility to hearing diseases, training and hearing fatigue. Individuals are capable of perceiving sound up to 22 kHz, and possibly higher.
A person can distinguish several sounds at the same time due to the fact that there can be several standing waves in the cochlea at the same time.
The ear is a complex vestibular-auditory organ that performs two functions: it perceives sound impulses and is responsible for the position of the body in space and the ability to maintain balance. This is a paired organ that is located in the temporal bones of the skull, limited externally by the auricles.
The organ of hearing and balance is represented by three sections: the outer, middle and inner ear, each of which performs its own specific functions.
The outer ear consists of the pinna and the external auditory canal. The auricle is a complex-shaped elastic cartilage covered with skin, its lower part, called the lobe, is skin fold, which consists of skin and adipose tissue.
The auricle in living organisms works as a receiver of sound waves, which are then transmitted to inner part hearing aid. The value of the auricle in humans is much smaller than in animals, so in humans it is practically motionless. But many animals, by moving their ears, are able to determine the location of the source of sound much more accurately than humans.
The folds of the human auricle contribute to the incoming ear canal sound - slight frequency distortions, depending on the horizontal and vertical localization of sound. This way the brain gets Additional information to clarify the location of the sound source. This effect is sometimes used in acoustics, including to create the sensation of surround sound when using headphones or hearing aids.
The function of the auricle is to catch sounds; its continuation is the cartilage of the external auditory canal, the length of which is on average 25-30 mm. The cartilaginous part of the auditory canal passes into the bone, and the entire external auditory canal is lined with skin containing sebaceous and sulfur glands, which are modified sweat glands. This passage ends blindly: it is separated from the middle ear by the eardrum. Sound waves captured by the auricle hit the eardrum and cause it to vibrate.
In turn, vibrations from the eardrum are transmitted to the middle ear.
Middle ear
The main part of the middle ear is tympanic cavity- a small space with a volume of about 1 cm³, located in the temporal bone. There are three auditory ossicles: the malleus, the incus and the stirrup - they transmit sound vibrations from the outer ear to the inner ear, simultaneously amplifying them.
The auditory ossicles, as the smallest fragments of the human skeleton, represent a chain that transmits vibrations. The handle of the malleus is closely fused with the eardrum, the head of the malleus is connected to the incus, and that, in turn, with its long process, is connected to the stapes. The base of the stapes closes the window of the vestibule, thus connecting to the inner ear.
The middle ear cavity is connected to the nasopharynx through eustachian tube, through which the average air pressure inside and outside the eardrum is equalized. When external pressure changes, the ears sometimes become blocked, which is usually resolved by yawning reflexively. Experience shows that ear congestion is solved even more effectively by swallowing movements or by blowing into a pinched nose at this moment.
Inner ear
Of the three sections of the organ of hearing and balance, the most complex is the inner ear, which, due to its intricate shape, is called the labyrinth. The bony labyrinth consists of the vestibule, cochlea and semicircular canals, but only the cochlea, filled with lymphatic fluids, is directly related to hearing. Inside the cochlea there is a membranous canal, also filled with liquid, on the lower wall of which there is a receptor apparatus of the auditory analyzer, covered with hair cells. Hair cells detect vibrations of the fluid filling the canal. Each hair cell is tuned to a specific sound frequency, with cells tuned to low frequencies located at the top of the cochlea, and high frequencies tuned to cells at the bottom of the cochlea. When hair cells die from age or for other reasons, a person loses the ability to perceive sounds of the corresponding frequencies.
Limits of Perception
The human ear nominally hears sounds in the range of 16 to 20,000 Hz. The upper limit tends to decrease with age. Most adults cannot hear sounds above 16 kHz. The ear itself does not respond to frequencies below 20 Hz, but they can be felt through the senses of touch.
The range of loudness of perceived sounds is enormous. But the eardrum in the ear is only sensitive to changes in pressure. Sound pressure level is usually measured in decibels (dB). The lower threshold of audibility is defined as 0 dB (20 micropascals), and the definition of the upper limit of audibility refers rather to the threshold of discomfort and then to hearing impairment, concussion, etc. This limit depends on how long we listen to the sound. The ear can tolerate short-term increases in volume up to 120 dB without consequences, but long-term exposure to sounds above 80 dB can cause hearing loss.
More careful studies of the lower limit of hearing have shown that the minimum threshold at which sound remains audible depends on frequency. This graph is called the absolute hearing threshold. On average, it has a region of greatest sensitivity in the range from 1 kHz to 5 kHz, although sensitivity decreases with age in the range above 2 kHz.
There is also a way to perceive sound without the participation of the eardrum - the so-called microwave auditory effect, when modulated radiation in the microwave range (from 1 to 300 GHz) affects the tissue around the cochlea, causing a person to perceive different sounds.
Sometimes a person can hear sounds in the low-frequency region, although in reality there were no sounds of this frequency. This happens because the vibrations of the basilar membrane in the ear are not linear and vibrations can occur in it with a difference frequency between two higher frequencies.
Synesthesia
One of the most unusual psychoneurological phenomena, in which the type of stimulus and the type of sensations that a person experiences do not coincide. Synaesthetic perception is expressed in the fact that in addition to ordinary qualities, additional, simpler sensations or persistent “elementary” impressions may arise - for example, color, smell, sounds, tastes, qualities of a textured surface, transparency, volume and shape, location in space and other qualities , not received through the senses, but existing only in the form of reactions. Such additional qualities may either arise as isolated sensory impressions or even manifest physically.
There is, for example, auditory synesthesia. This is the ability of some people to "hear" sounds when observing moving objects or flashes, even if they are not accompanied by actual sound phenomena.
It should be borne in mind that synesthesia is rather a psychoneurological feature of a person and is not mental disorder. This perception of the surrounding world can be felt a common person through the use of certain drugs.
There is no general theory of synesthesia (a scientifically proven, universal idea about it) yet. Currently, there are many hypotheses and a lot of research is being conducted in this area. Original classifications and comparisons have already appeared, and certain strict patterns have emerged. For example, we scientists have already found out that synesthetes have a special nature of attention - as if “preconscious” - to those phenomena that cause synesthesia in them. Synesthetes have a slightly different brain anatomy and a radically different activation of the brain to synaesthetic “stimuli.” And researchers from the University of Oxford (UK) conducted a series of experiments during which they found that the cause of synesthesia may be overexcitable neurons. The only thing that can be said for sure is that such perception is obtained at the level of brain function, and not at the level of primary perception of information.
Conclusion
Pressure waves pass through the outer ear, eardrum and ossicles of the middle ear, reaching the fluid-filled inner ear shaped like a snail. The liquid, oscillating, hits a membrane covered with tiny hairs, cilia. The sinusoidal components of a complex sound cause vibrations in various parts of the membrane. The cilia vibrating together with the membrane excite the nerve fibers associated with them; a series of pulses appear in them, in which the frequency and amplitude of each component of a complex wave are “encoded”; this data is electrochemically transmitted to the brain.
Of the entire spectrum of sounds, the audible range is primarily distinguished: from 20 to 20,000 hertz, infrasound (up to 20 hertz) and ultrasound - from 20,000 hertz and above. A person cannot hear infrasounds and ultrasounds, but this does not mean that they do not affect him. It is known that infrasounds, especially below 10 hertz, can influence the human psyche and cause depression. Ultrasounds can cause astheno-vegetative syndromes, etc.
The audible part of the sound range is divided into low-frequency sounds - up to 500 hertz, mid-frequency - 500-10,000 hertz and high-frequency - over 10,000 hertz.
This division is very important, since the human ear is not equally sensitive to different sounds. The ear is most sensitive to a relatively narrow range of mid-frequency sounds from 1000 to 5000 hertz. To lower and higher frequency sounds, sensitivity drops sharply. This leads to the fact that a person is able to hear sounds with an energy of about 0 decibels in the mid-frequency range and not hear low-frequency sounds of 20-40-60 decibels. That is, sounds with the same energy in the mid-frequency range can be perceived as loud, but in the low-frequency range as quiet or not be heard at all.
This feature of sound was not formed by nature by chance. The sounds necessary for its existence: speech, sounds of nature, are mainly in the mid-frequency range.
The perception of sounds is significantly impaired if other sounds, noises similar in frequency or harmonic composition, are heard at the same time. This means, on the one hand, the human ear does not perceive low-frequency sounds well, and, on the other hand, if there is extraneous noise in the room, then the perception of such sounds can be further disturbed and distorted.
It is known that a person receives 90% of information about the world around him through vision. It would seem that there is not much left for hearing, but in fact, the human organ of hearing is not only a highly specialized analyzer of sound vibrations, but also a very powerful tool communications. Doctors and physicists have long been concerned with the question: is it possible to accurately determine the range of human hearing in different conditions, does hearing differ between men and women, are there “particularly outstanding” record holders who hear inaccessible sounds, or can produce them? Let's try to answer these and some other related questions in more detail.
But before you understand how many hertz the human ear hears, you need to understand such a fundamental concept as sound, and in general, understand what exactly is measured in hertz.
Sound vibrations are a unique way of transmitting energy without transferring matter; they are elastic vibrations in any medium. When it comes to ordinary human life, such a medium is air. They contain gas molecules that can transmit acoustic energy. This energy represents the alternation of bands of compression and tension of the density of the acoustic medium. In an absolute vacuum, sound vibrations cannot be transmitted.
Any sound is a physical wave and contains all the necessary wave characteristics. This is frequency, amplitude, decay time, if we are talking about a damped free oscillation. Let's look at this using simple examples. Let us imagine, for example, the sound of the open G string on a violin when it is played with a bow. We can define the following characteristics:
- quiet sound or loud. It is nothing more than the amplitude, or strength, of sound. More loud sound a large vibration amplitude corresponds, and a smaller amplitude corresponds to a quiet sound. A sound with greater strength can be heard at a greater distance from the point of origin;
- sound duration. This is clear to everyone, and everyone is able to distinguish the sound of a drum roll from the extended sound of a choral organ melody;
- pitch, or frequency of sound vibration. It is this fundamental characteristic that helps us distinguish “squeaking” sounds from the bass register. If there were no frequency of sound, music would only be possible in the form of rhythm. Frequency is measured in hertz, and 1 hertz is equal to one vibration per second;
- timbre of sound. It depends on the admixture of additional acoustic vibrations - formants, but it can be explained in simple words very easy: even with eyes closed we understand that it is the violin that sounds, and not the trombone, even if they have exactly the same characteristics listed above.
The timbre of sound can be compared to numerous flavor shades. In total, we have bitter, sweet, sour and salty tastes, but these four characteristics are far from exhausting the various taste sensations. The same thing happens with timbre.
Let us dwell in more detail on the pitch of sound, since it is on this characteristic that the acuity of hearing and the range of perceived acoustic vibrations depend to the greatest extent. What is the audio frequency range?
Hearing range under ideal conditions
The frequencies perceived by the human ear under laboratory or ideal conditions are in a relatively wide band from 16 Hertz to 20,000 Hertz (20 kHz). Everything lower and higher cannot be heard by the human ear. It's about about infrasound and ultrasound. What it is?
Infrasound
It cannot be heard, but the body can feel it, like the work of a large bass speaker - a subwoofer. These are infrasonic vibrations. Everyone knows perfectly well that if you constantly loosen the bass string on a guitar, then, despite the continued vibrations, the sound disappears. But these vibrations can still be felt with your fingertips when you touch the string.
Many people operate in the infrasound range internal organs human: contraction of the intestines, dilation and constriction of blood vessels, and many biochemical reactions occur. Very strong infrasound can cause a serious painful condition, even waves of panic horror, this is the basis of the action of infrasonic weapons.
Ultrasound
On the opposite side of the spectrum are very high-pitched sounds. If the sound has a frequency above 20 kilohertz, then it stops “squeaking” and becomes inaudible to the human ear in principle. It becomes ultrasound. Ultrasound has great application in the national economy, ultrasound diagnostics is based on it. With the help of ultrasound, ships navigate the sea, avoiding icebergs and shallow waters. Using ultrasound, specialists find voids in solid metal structures, such as rails. Everyone saw how workers rolled a special flaw detection cart along the rails, generating and receiving high-frequency acoustic vibrations. Ultrasound is used the bats to accurately find your way in the dark without bumping into cave walls, whales and dolphins.
It is known that the ability to distinguish high-pitched sounds decreases with age, and children can hear them best. Modern research show that already at the age of 9-10 years, children’s hearing range begins to gradually decrease, and in older people, the audibility of high frequencies is much worse.
To hear how older people perceive music, you simply need to turn down one or two rows of high frequencies on the multi-band equalizer in your cell phone player. The resulting uncomfortable “mumbling, as if from a barrel,” will be an excellent illustration of how you yourself will hear after the age of 70.
Plays an important role in hearing loss poor nutrition, drinking and smoking, postponing cholesterol plaques on the walls of blood vessels. Statistics from ENT doctors claim that people with the first blood group develop hearing loss more often and faster than others. Hearing loss is brought on by excess weight and endocrine pathology.
Hearing range under normal conditions
If we cut off the “marginal areas” of the sound spectrum, then not much is available for a comfortable human life: this is the range from 200 Hz to 4000 Hz, which almost completely corresponds to the range of the human voice, from deep basso-profundo to high coloratura soprano. However, even with comfortable conditions, a person’s hearing is constantly deteriorating. Typically, the greatest sensitivity and susceptibility in adults under the age of 40 is at the level of 3 kilohertz, and at the age of 60 years or more it decreases to 1 kilohertz.
Hearing range in men and women
Currently, gender segregation is not encouraged, but men and women do perceive sound differently: women are able to hear better in the high range, and the age-related involution of sound in the high frequency region is slower for them, while men perceive high sounds somewhat worse. It would seem logical to assume that men hear better in the bass register, but this is not the case. The perception of bass sounds is almost the same in both men and women.
But there are women who are unique in “generating” sounds. Thus, the voice range of the Peruvian singer Ima Sumac (almost five octaves) extended from the sound “B” of the large octave (123.5 Hz) to “A” of the fourth octave (3520 Hz). An example of her unique vocals can be found below.
At the same time, there is a rather large difference in the functioning of the speech apparatus between men and women. Women produce sounds from 120 to 400 hertz, and men from 80 to 150 Hz, according to average data.
Various scales to indicate hearing range
At the beginning we talked about how pitch is not the only characteristic of sound. Therefore, there are different scales according to different ranges. The sound heard by the human ear can be, for example, soft and loud. The simplest and most acceptable clinical practice sound loudness scale - one that measures the sound pressure perceived by the eardrum.
This scale is based on the lowest energy vibration of sound, which can be transformed into a nerve impulse and cause a sound sensation. This is the threshold of auditory perception. The lower the perception threshold, the higher the sensitivity, and vice versa. Experts distinguish between sound intensity, which is a physical parameter, and loudness, which is a subjective value. It is known that a sound of strictly the same intensity will be perceived by a healthy person and a person with hearing loss as two different sounds, louder and quieter.
Everyone knows how in an ENT doctor’s office the patient stands in a corner, turns away, and the doctor from the next corner checks the patient’s perception of whispered speech, pronouncing individual numbers. This is the simplest example primary diagnosis hearing loss.
It is known that the subtle breathing of another person is 10 decibels (dB) of sound pressure intensity, a normal conversation in home environment corresponds to 50 dB, the howl of a fire siren is 100 dB, and a jet plane taking off near the pain threshold is 120 decibels.
It may be surprising that all the enormous intensity of sound vibrations fits on such a small scale, but this impression is deceptive. This is a logarithmic scale, and each subsequent step is 10 times more intense than the previous one. A scale for assessing the intensity of earthquakes was built using the same principle, with only 12 points.
February 7, 2018
Often people (even those who are well versed in the subject) experience confusion and difficulty in clearly understanding how exactly the frequency range of sound heard by humans is divided into general categories (low, mid, high) and into narrower subcategories (upper bass, lower mid and so on.). At the same time, this information is extremely important not only for experiments with car audio, but also useful for general development. Knowledge will definitely come in handy when setting up an audio system of any complexity and, most importantly, will help to correctly evaluate the strengths or weak sides this or that acoustic system or the nuances of the music listening room (in our case, the car interior is more relevant), because it has a direct impact on the final sound. If you have a good and clear understanding of the predominance of certain frequencies in the sound spectrum by ear, then you can easily and quickly evaluate the sound of a particular musical composition, while clearly hearing the influence of room acoustics on the coloring of the sound, the contribution of the acoustic system itself to the sound, and more subtly to sort out all the nuances, which is what the ideology of “hi-fi” sound strives for.
Division of the audible range into three main groups
The terminology for dividing the audible frequency spectrum came to us partly from the musical world, partly from the scientific world, and in general it is familiar to almost everyone. The simplest and most understandable division that can test the frequency range of sound in general looks like this:
- Low frequencies. The limits of the low frequency range are within 10 Hz (lower limit) - 200 Hz (upper limit). The lower limit begins precisely at 10 Hz, although in the classical view a person is able to hear from 20 Hz (everything below falls into the infrasound region), the remaining 10 Hz can still be partially audible, and can also be felt tactilely in the case of deep low bass and even influence a person's psychological mood.
The low-frequency range of sound has the function of enrichment, emotional saturation and final response - if the dip in the low-frequency part of the acoustics or the original recording is strong, then this will not in any way affect the recognition of a particular composition, melody or voice, but the sound will be perceived as meager, depleted and mediocre, while subjectively it will be sharper and sharper in terms of perception, since the mid and high frequencies will protrude and prevail against the background of the absence of a good rich bass region. 
A fairly large number of musical instruments reproduce sounds in the low frequency range, including male vocals that can go down to 100 Hz. The most pronounced instrument, which plays from the very beginning of the audible range (from 20 Hz), can safely be called the wind organ. - Mid frequencies. The boundaries of the mid frequency range are within 200 Hz (lower limit) - 2400 Hz (upper limit). The mid-range will always be fundamental, defining and actually form the basis of the sound or music of a composition, therefore its importance is difficult to overestimate.
This can be explained in different ways, but mainly this feature of human auditory perception is determined by evolution - it has happened over many years of our formation that the hearing aid most acutely and clearly captures the mid-frequency range, because within its boundaries lies human speech, and it is the main tool for effective communication and survival. This also explains some nonlinearity of auditory perception, always aimed at the predominance of mid-frequencies when listening to music, because our hearing aid is most sensitive to this range, and also automatically adapts to it, as if “amplifying” it more against the background of other sounds. 
The absolute majority of sounds, musical instruments or vocals are found in the middle range, even if a narrow range above or below is affected, the range still usually extends to the upper or lower middle. Accordingly, vocals (both male and female), as well as almost all well-known instruments, such as guitar and other strings, piano and other keyboards, wind instruments, etc., are located in the mid-frequency range. - High frequencies. The limits of the high frequency range are within 2400 Hz (lower limit) - 30000 Hz (upper limit). The upper limit, as in the case of the low-frequency range, is somewhat arbitrary and also individual: the average person cannot hear above 20 kHz, but there are rare people with sensitivity up to 30 kHz.
Also, a number of musical overtones can theoretically extend into the region above 20 kHz, and as is known, overtones are ultimately responsible for the color of the sound and the final timbral perception of the overall sound picture. Seemingly “inaudible” ultrasonic frequencies can clearly influence psychological condition person, although they will not be tapped in the usual manner. Otherwise, the role of high frequencies, again by analogy with low frequencies, is more enriching and complementary. Although the high-frequency range has a much greater effect on recognition specific sound, reliability and preservation of the original timbre, rather than the low-frequency section. High frequencies give music tracks "airiness", transparency, purity and clarity. 
Many musical instruments also play in the high frequency range, including vocals that can reach the region of 7000 Hz and above with the help of overtones and harmonics. The most pronounced group of instruments in the high-frequency segment are strings and winds, and cymbals and violin reach almost the upper limit of the audible range (20 kHz) in sound.
In any case, the role of absolutely all frequencies of the range audible to the human ear is impressive and problems in the path at any frequency will most likely be clearly visible, especially to a trained hearing aid. The goal of reproducing high-precision sound of “hi-fi” class (or higher) is the reliable and maximally even sound of all frequencies with each other, as it happened at the time the phonogram was recorded in the studio. The presence of strong dips or peaks in the frequency response of the speaker system indicates that, due to its design features, it is not capable of reproducing music as originally intended by the author or sound engineer at the time of recording. 
Listening to music, a person hears the combination of sounds of instruments and voices, each of which sounds in some part of the frequency range. Some instruments may have a very narrow (limited) frequency range, while for others, on the contrary, it can literally extend from the lower to the upper audible limit. It must be taken into account that despite the same intensity of sounds at different frequency ranges, the human ear perceives these frequencies with different loudness, which is again due to the mechanism of the biological structure of the hearing aid. The nature of this phenomenon is also largely explained by the biological need to adapt primarily to the mid-frequency sound range. So in practice, a sound with a frequency of 800 Hz at an intensity of 50 dB will be perceived subjectively by ear as louder compared to a sound of the same intensity, but with a frequency of 500 Hz.
Moreover, different sound frequencies flooding the audible frequency range of sound will have different threshold pain sensitivity! Pain threshold the reference is considered to be at an average frequency of 1000 Hz with a sensitivity of approximately 120 dB (may vary slightly depending on the individual characteristics of the person). As in the case of uneven intensity perception at different frequencies when normal levels loudness, approximately the same dependence is observed in relation to the pain threshold: it occurs most quickly at mid-frequencies, but at the edges of the audible range the threshold becomes higher. For comparison, the pain threshold at an average frequency of 2000 Hz is 112 dB, while the pain threshold at a low frequency of 30 Hz will be 135 dB. The pain threshold at low frequencies is always higher than at medium and high frequencies. 
A similar disparity is observed in relation to hearing threshold- this is the lower threshold after which sounds become audible to the human ear. Conventionally, the hearing threshold is considered to be 0 dB, but again it is valid for the reference frequency of 1000 Hz. If, for comparison, we take a low-frequency sound of 30 Hz, then it will become audible only at a wave radiation intensity of 53 dB.
The listed features of human auditory perception, of course, have a direct impact when the question of listening to music and achieving a certain psychological effect of perception is raised. We remember from that sounds with an intensity above 90 dB are harmful to health and can lead to degradation and significant hearing impairment. However, a low-intensity sound that is too quiet will suffer from severe frequency unevenness due to biological features auditory perception, which is nonlinear in nature. Thus, a musical path with a volume of 40-50 dB will be perceived as depleted, with a pronounced lack (one might say failure) of low and high frequencies. This problem has been well known for a long time; to combat it, a well-known function called tone compensation, which, through equalization, equalizes the levels of low and high frequencies close to the mid-level, thereby eliminating unwanted dip without the need to raise the volume level, making the audible frequency range of sound subjectively uniform in the degree of distribution of sound energy. 
Taking into account the interesting and unique features of human hearing, it is useful to note that as the sound volume increases, the frequency nonlinearity curve levels out, and at approximately 80-85 dB (and above), sound frequencies will become subjectively equivalent in intensity (with a deviation of 3-5 dB). Although the leveling does not occur completely and a smoothed but curved line will still be visible on the graph, which will maintain a tendency towards the predominance of the intensity of the middle frequencies compared to the rest. In audio systems, such unevenness can be resolved either with the help of an equalizer, or with the help of separate volume controls in systems with separate channel amplification.
Dividing the audible range into smaller subgroups
In addition to the generally accepted and well-known division into three general groups, sometimes there is a need to consider this or that narrow part in more detail and in detail, thereby dividing the frequency range of sound into even smaller “fragments”. Thanks to this, a more detailed division has appeared, using which you can quickly and quite accurately designate the expected segment of the sound range. Consider this division:
A small selected number of instruments fall into the region of the lowest bass and especially sub-bass: double bass (40-300 Hz), cello (65-7000 Hz), bassoon (60-9000 Hz), tuba (45-2000 Hz), horns (60-5000 Hz), bass guitar (32-196 Hz), bass drum (41-8000 Hz), saxophone (56-1320 Hz), piano (24-1200 Hz), synthesizer (20-20000 Hz) , organ (20-7000 Hz), harp (36-15000 Hz), contrabassoon (30-4000 Hz). The indicated ranges take into account all instrument harmonics.
Therefore, it is the upper bass that is responsible for the attack, pressure and musical drive, and also only this narrow segment of the sound range is capable of giving the listener the feeling of the legendary “punch” (from the English punch - blow), when a powerful sound is perceived as tangible and with a strong blow in the chest. Thus, you can recognize a well-formed and correct fast upper bass in a music system by the high-quality development of an energetic rhythm, a collected attack and by the good design of instruments in the lower register of notes, such as cello, piano or wind instruments. In audio systems, it is most advisable to give a segment of the upper bass range to midbass speakers with a fairly large diameter of 6.5"-10" and with good power characteristics and a strong magnet. The approach is explained by the fact that it is the speakers of this configuration that will be able to fully reveal the energy potential inherent in this very demanding region of the audible range. 
But don’t forget about the detail and intelligibility of sound; these parameters are just as important in the process of recreating a particular musical image. Since the upper bass is already well localized/defined in space by ear, the range above 100 Hz must be given exclusively to the front-mounted speakers, which will shape and build the scene. In the upper bass segment, stereo panorama can be heard perfectly, if it is provided for by the recording itself.
The upper bass region already covers a fairly large number of instruments and even low-pitched male vocals. Therefore, among the instruments are the same ones that played low bass, but many others are added to them: toms (70-7000 Hz), snare drum (100-10000 Hz), percussion (150-5000 Hz), tenor trombone (80-10000 Hz), trumpet (160-9000 Hz), tenor saxophone (120-16000 Hz), alto saxophone (140-16000 Hz), clarinet (140-15000 Hz), alto violin (130-6700 Hz), guitar (80-5000 Hz). The indicated ranges take into account all instrument harmonics.
In this range, the lower harmonics and overtones that fill the voice are concentrated, so it is extremely important for the correct transmission of vocals and saturation. Also, it is in the lower middle that the entire energy potential of the performer’s voice is located, without which there will be no corresponding impact and emotional response. By analogy with the transmission of the human voice, many live instruments also hide their energy potential in this part of the range, especially those whose lower audible limit starts from 200-250 Hz (oboe, violin). The lower middle allows you to hear the melody of the sound, but does not make it possible to clearly distinguish instruments. Accordingly, the lower middle is responsible for the correct design of most instruments and voices, saturating the latter and making them recognizable by their timbre coloring. Also, the lower mids are extremely demanding regarding the correct transmission of the full bass range, since it “picks up” the drive and attack of the main striking bass and is supposed to properly support it and smoothly “finish” it, gradually reducing it to nothing. The sensations of sound purity and bass intelligibility lie precisely in this area, and if there are problems in the lower middle due to excess or the presence of resonant frequencies, then the sound will tire the listener, it will be dirty and slightly booming. 
If there is a shortage in the lower mids, then the correct feeling of the bass and the reliable transmission of the vocal part will suffer, which will be devoid of pressure and energy return. The same applies to most instruments, which without the support of the lower middle will lose “their face”, will become incorrectly shaped and their sound will noticeably become poorer, even if it remains recognizable, it will no longer be as complete.
When building an audio system, the range of the lower middle and above (up to the upper) is usually given to mid-frequency speakers (MF), which, without a doubt, should be located in the front part in front of the listener and build the stage. For these speakers, the size is not so important, it can be 6.5" or lower, but detail and the ability to reveal the nuances of sound are important, which is achieved by the design features of the speaker itself (diffuser, suspension and other characteristics). 
Also, for the entire mid-frequency range, correct localization is vitally important, and literally the slightest tilt or turn of the speaker can have a noticeable impact on the sound from the point of view of correctly realistically recreating the images of instruments and vocals in space, although this will largely depend on the design features of the speaker cone itself.
The lower middle covers almost all existing instruments and human voices, although it does not play a fundamental role, but is still very important for the full perception of music or sounds. Among the instruments there will be the same set that was capable of playing the lower range of the bass region, but others are added to them that start from the lower middle: cymbals (190-17000 Hz), oboe (247-15000 Hz), flute (240-17000 Hz), 14500 Hz), violin (200-17000 Hz). The indicated ranges take into account all instrument harmonics.
If the middle fails, the sound becomes boring and inexpressive, loses its sonority and brightness, the vocals cease to bewitch and actually fade away. The middle is also responsible for the intelligibility of basic information coming from instruments and vocals (to a lesser extent, since consonant sounds are higher in the range), helping to distinguish them well by ear. Majority existing tools come to life in this range, becoming energetic, informative and tangible, the same thing happens with vocals (especially female ones), which are filled with energy in the middle. 
The mid-frequency fundamental range covers the vast majority of instruments that have already been listed earlier, and also reveals the full potential of male and female vocals. Only a few selected instruments begin their life at medium frequencies, playing in a relatively narrow range initially, for example, the small flute (600-15000 Hz).
But overemphasizing this range has an extremely undesirable effect on the sound picture, because it begins to noticeably hurt the ears, irritate and even cause painful discomfort. Therefore, the upper middle requires a delicate and careful attitude, because Because of problems in this area, it is very easy to ruin the sound, or, on the contrary, to make it interesting and worthy. Typically, the color in the upper middle area largely determines the subjective genre of the speaker system. Thanks to the upper middle, vocals and many instruments are finally formed, they become clearly distinguishable by ear and sound intelligibility appears. This is especially true for the nuances of reproducing the human voice, because it is in the upper middle that the spectrum of consonant sounds is placed and the vowels that appeared in the early ranges of the middle continue. In a general sense, the upper midrange favorably emphasizes and fully reveals those instruments or voices that are rich in upper harmonics and overtones. In particular, female vocals and many bowed, stringed and wind instruments are revealed truly vividly and naturally in the upper middle. 
The vast majority of instruments still play in the upper middle, although many are already represented only in the form of wrappers and harmonics. The exception is some rare ones, initially characterized by a limited low-frequency range, for example, the tuba (45-2000 Hz), which ends its existence completely in the upper middle.
They practically do not play a role in distinguishing instruments and recognizing voices, although the lower upper remains an extremely informative and fundamental area. Essentially, these frequencies outline the musical images of instruments and vocals, they indicate their presence. If the lower high segment of the frequency range fails, the speech will become dry, lifeless and incomplete, approximately the same thing happens with instrumental parts - brightness is lost, the very essence of the sound source is distorted, it becomes clearly unfinished and under-formed. In any normal audio system, the role of high frequencies is taken over by a separate speaker called a tweeter (high-frequency). Usually small in size, it is undemanding in terms of power input (within reasonable limits) similar to the middle and especially the low-end sections, but it is also extremely important for the sound to play correctly, realistically and at least beautifully. The tweeter covers the entire audible high-frequency range from 2000-2400 Hz to 20,000 Hz. In the case of high-frequency speakers, almost by analogy with the midrange section, the correct physical location and directionality is very important, since tweeters are maximally involved not only in the formation of the sound stage, but also in the process of fine-tuning it. 
With the help of tweeters, you can control the stage in many ways, bring performers closer/farther away, change the shape and presentation of instruments, play with the color of the sound and its brightness. As in the case of adjusting midrange speakers, the correct sound of tweeters is affected by almost everything, and often very, very sensitively: the rotation and tilt of the speaker, its vertical and horizontal location, distance from nearby surfaces, etc. However, the success of proper tuning and the finickiness of the HF section depends on the design of the speaker and its polar pattern.
Instruments that play to the lower treble do so primarily through harmonics rather than fundamental notes. Otherwise, in the lower-high range, almost all of the same ones “live” as were in the mid-frequency segment, i.e. almost all existing ones. The same goes for the voice, which is especially active in the lower high frequencies, with particular brightness and influence being heard in female vocal parts.
In fact, the presented segment of the range is comparable to increased clarity and detail of sound: if there is no dip in the mid-high, then the sound source is well localized mentally in space, concentrated at a certain point and expressed by a feeling of a certain distance; and vice versa, if there is a lack of lower top, then the clarity of the sound seems to be blurred and the images are lost in space, the sound becomes cloudy, compressed and synthetically unrealistic. Accordingly, regulation of the lower high frequency segment is comparable to the ability to virtually “move” the sound stage in space, i.e. move it away or bring it closer. 
The mid-high frequencies ultimately provide the desired effect of presence (or rather, they complete it in full, since the basis of the effect is deep and penetrating low frequencies), thanks to these frequencies the instruments and voice become as realistic and reliable as possible. We can also say about the mid-highs that they are responsible for the detail in the sound, for numerous small nuances and overtones both in relation to the instrumental part and in the vocal parts. At the end of the mid-high segment, “air” and transparency begin, which can also be quite clearly felt and influence perception.
Despite the fact that the sound is steadily declining, in this part of the range the following are still active: male and female vocals, bass drum (41-8000 Hz), toms (70-7000 Hz), snare drum (100-10000 Hz) , cymbals (190-17000 Hz), air support trombone (80-10000 Hz), trumpet (160-9000 Hz), bassoon (60-9000 Hz), saxophone (56-1320 Hz), clarinet (140-15000 Hz), oboe (247-15000 Hz), flute (240-14500 Hz), small flute (600-15000 Hz), cello (65-7000 Hz), violin (200-17000 Hz), harp (36-15000 Hz ), organ (20-7000 Hz), synthesizer (20-20000 Hz), timpani (60-3000 Hz).
In addition, in addition to the immediate audible part, the region of the upper highs, smoothly turning into ultrasonic frequencies, can still have a certain psychological effect: even if these sounds are not heard clearly, the waves are emitted into space and can be perceived by a person, while more at the level mood formation. They also ultimately affect the sound quality. In general, these frequencies are the most subtle and gentle in the entire range, but they are also responsible for the feeling of beauty, elegance, and sparkling aftertaste of music. If there is a lack of energy in the upper high range, it is quite possible to feel discomfort and musical understatement. In addition, the capricious range of the upper treble gives the listener a sense of spatial depth, as if immersed deep into the stage and enveloping the sound. However, an excess of sound saturation in the designated narrow range can make the sound excessively “sandy” and unnaturally thin. 
When discussing the upper high frequency range, it is also worth mentioning the tweeter called a “super tweeter”, which is actually a structurally expanded version of a regular tweeter. Such a speaker is designed to cover a larger part of the range in the upper direction. If the operating range of a conventional tweeter ends at the supposed limiting mark, above which the human ear theoretically does not perceive sound information, i.e. 20 kHz, then the super tweeter can raise this limit to 30-35 kHz. The idea behind the implementation of such a sophisticated speaker is very interesting and curious, it comes from the world of “hi-fi” and “hi-end”, where it is believed that no frequencies can be ignored in the musical path and, even if we do not hear them directly, they are still initially present during the live performance of a particular composition, which means they can indirectly have some influence. The situation with a super tweeter is complicated only by the fact that not all equipment (sound sources/players, amplifiers, etc.) are capable of outputting a signal in the full range, without cutting off frequencies from above. The same is true for the recording itself, which is often done with frequency range cutting and loss of quality.
The division of the audible frequency range into conventional segments in reality looks approximately this way as described above; with the help of division, it is easier to understand problems in the sound path in order to eliminate them or to level out the sound. Despite the fact that each person imagines some unique standard image of sound that is understandable only to him, in accordance only with his taste preferences, the nature of the original sound tends to balance, or rather to the averaging of all sounding frequencies. Therefore, the correct studio sound is always balanced and calm, the entire spectrum of sound frequencies in it tends to a flat line on the frequency response (amplitude-frequency response) graph. The same direction is trying to implement uncompromising “hi-fi” and “hi-end”: to obtain the most even and balanced sound, without peaks and dips throughout the entire audible range. Such a sound may seem boring and inexpressive in nature to the average inexperienced listener, lacking brightness and of no interest, but it is precisely this sound that is truly correct in fact, striving for balance by analogy with how the laws of the universe itself in which we live manifest themselves .
One way or another, the desire to recreate a certain sound character within the framework of one’s audio system lies entirely on the preferences of the listener himself. Some people like a sound with a predominance of powerful lows, others like the increased brightness of “raised” highs, others can spend hours enjoying harsh vocals emphasized in the middle... There can be a huge number of perception options, and information about the frequency division of the range into conditional segments will just help anyone who wants to create the sound of their dreams, only now with a more complete understanding of the nuances and subtleties of the laws to which sound as a physical phenomenon is subject. 
Understanding the process of saturation with certain frequencies of the sound range (filling it with energy in each of the sections) in practice will not only facilitate the setup of any audio system and make it possible to build a stage in principle, but will also provide invaluable experience in assessing the specific nature of the sound. With experience, a person will be able to instantly identify sound defects by ear, and very accurately describe the problems in a certain part of the range and suggest a possible solution to improve the sound picture. Sound adjustments can be made various methods, where you can use an equalizer as “levers,” for example, or “play” with the location and direction of the speakers - thereby changing the nature of early wave reflections, eliminating standing waves, etc. This will be a “completely different story” and a topic for separate articles.
Frequency range of the human voice in musical terminology
The human voice plays a separate and distinct role in music as a vocal part, because the nature of this phenomenon is truly amazing. The human voice is so multifaceted and its range (compared to musical instruments) the widest, with the exception of some instruments, such as the piano. 
Moreover, in different ages a person can make sounds of different pitches, childhood up to ultrasonic heights, in adulthood male voice quite capable of going extremely low. Here, as before, individual characteristics are extremely important. vocal cords person, because There are people who can amaze with their voices in the range of 5 octaves!
- Children's
- Alto (low)
- Soprano (high)
- Treble (high for boys)
- Men's
- Bass profundo (super low) 43.7-262 Hz
- Bass (low) 82-349 Hz
- Baritone (medium) 110-392 Hz
- Tenor (high) 132-532 Hz
- Tenor-altino (super high) 131-700 Hz
- Women's
- Contralto (low) 165-692 Hz
- Mezzo-soprano (medium) 220-880 Hz
- Soprano (high) 262-1046 Hz
- Coloratura soprano (super high) 1397 Hz
The person is deteriorating, and over time we lose the ability to detect a certain frequency.
Video made by the channel AsapSCIENCE, is a kind of age-related hearing loss test that will help you find out your hearing limits.
Various sounds are played in the video, starting at 8000 Hz, which means your hearing is not impaired.
The frequency then increases and this indicates the age of your hearing based on when you stop hearing a particular sound.
So if you hear a frequency:
12,000 Hz – you are under 50 years old
15,000 Hz – you are under 40 years old
16,000 Hz – you are under 30 years old
17,000 – 18,000 – you are under 24 years old
19,000 – you are under 20 years old
If you want the test to be more accurate, you should set the video quality to 720p or better yet 1080p, and listen with headphones.
Hearing test (video)
Hearing loss
If you heard all the sounds, you are most likely under 20 years old. Results depend on sensory receptors in your ear, called hair cells which become damaged and degenerate over time.
This type of hearing loss is called sensorineural hearing loss. A variety of infections, medications, and autoimmune diseases can cause this disorder. The outer hair cells, which are tuned to detect higher frequencies, are usually the first to die, causing the effects of age-related hearing loss, as demonstrated in this video.
Human hearing: interesting facts
1. Among healthy people frequency range that the human ear can detect ranges from 20 (lower than the lowest note on a piano) to 20,000 Hertz (higher than the highest note on a small flute). However, the upper limit of this range decreases steadily with age.
2. People talk to each other at a frequency from 200 to 8000 Hz, and the human ear is most sensitive to a frequency of 1000 – 3500 Hz
3. Sounds that are above the limit of human audibility are called ultrasound, and those below - infrasound.
4. Ours my ears don't stop working even in my sleep, continuing to hear sounds. However, our brain ignores them.
5. Sound travels at 344 meters per second. A sonic boom occurs when an object exceeds the speed of sound. Sound waves in front and behind the object collide and create a shock.
6. Ears - self-cleaning organ. Pores in the ear canal secrete earwax, and tiny hairs called cilia push the wax out of the ear
7. The sound of a baby crying is approximately 115 dB, and it's louder than a car horn.
8. In Africa there is a Maaban tribe who live in such silence that even in old age they hear whispers up to 300 meters away.
9. Level bulldozer sound idling is about 85 dB (decibels), which can cause hearing damage after just one 8-hour day.
10. Sitting in front speakers at a rock concert, you're exposing yourself to 120 dB, which begins to damage your hearing after just 7.5 minutes.
