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The auditory system provides a sound wave, its conversion into nerve impulses, their transmission to the auditory centers, analysis and integration of sound information. The frequency, strength and timbre of sounds are differentiated. With the help of speech, people communicate. Thanks to auditory memory, you can find out whether a voice belongs to a specific person, animal or sound - an object. The auditory system provides tuning of the middle ear and sensitive cells of the spiral organ to sounds of a certain strength and frequency. With strong sounds, it, to a certain extent, lowers sound conduction, performing a protective function. With the help of the hearing organ, with a sudden strong sound, protective and indicative reactions of the body are realized: blinking (ankylosing spondylitis reflex), narrowing of the pupil (cochleopupillary reflex Shurygin), turning the head towards the sound source.

An adequate irritant to the organ of hearing is sound, which is the oscillatory movement of particles of an elastic medium propagating in the form of waves in air, liquids and solids.

Sounds of the same frequency or clear sounds (tones of a tuning fork, audiometer) are rare in nature. They are characterized by sinusoidal, that is, periodic oscillations. More often we are surrounded by complex sounds and noises with overtones and aperiodic vibrations.

The parameters of sound waves are amplitude, frequency, phase, length, period, duration, spectrum and others.

Sound propagating in a medium is a wave (Fig. 1.2.1) with the phases of condensation (increase of atmospheric pressure) and rarefaction (decrease of atmospheric pressure) of its particles. The distance between the middle and extreme position of the oscillating body is called the amplitude of the oscillations. The amplitude of the periodic pressure fluctuations of a propagating wave is called sound pressure. The wavelength is the distance between two areas of compression or rarefaction of it, and the frequency is the number of oscillations (compressions or rarefactions) per second. The unit of measurement for the wavelength is 1 m, and the frequency is hertz (Hz), that is, one oscillation per second. The time during which a sound wave makes a complete oscillation is called the oscillation period. The propagation velocity of acoustic waves in air is 343 m / s, water - 1480 m / s and solids - 2000 m / s at a temperature of 200 C.

Fig. 1.2.1.

The absolute unit of measurement of acoustic quantity by sound pressure is Pascal (Pa) .1Pa = 1H.m-2. The absolute threshold of human hearing at a frequency of 1000 Hz is 2.10-5 Pa, which is taken as standard sound pressure (p0).

A relative unit of measure characterizes how much the value of a given acoustic quantity exceeds its standard value. Bel and decibels (dB) are taken as relative units.

Sound pressure, expressed in decibels relative to 2.10-5 Pa, is called the sound pressure level (SPL) or SPL (Sound Pressure Level), which is calculated using the logarithm according to the formula:

SPL = k. Lg? /? 0

At k = 2, the unit of ultrasound is Bel, and at k = 20 it is decibel / dB /.

The relative energy unit of a sound wave is calculated using the intensity level (L).

L = k. Lg I / I0

The threshold intensity (I0) is the energy threshold of sound audibility in Watts at a frequency of 1000 Hz, which is 10-12W.m-2. At k = 1, the unit of the intensity level is Bel, and at k = 10 it is the decibel (dB). Three values: p = 2.10-5 Pa; I = 10-12 W.m-2 and L = 0 dB characterize the same sound, that is, they essentially correspond to the thresholds of audibility in terms of sound pressure, power and sound intensity level.

Ia? En. 1.2.2. iieacaii,? oi i? e 20 aA caoeiaia aaaeaiea (p) corresponds to a 10-fold increase in the absolute threshold sound pressure (p0 = 2? 10-5 Pa), at 40 dB it increases 100 times, at 60 dB - 1000 times, at 80 dB - 10,000 times, at 100 dB - 100,000 times, etc.


In fig. 1.2.3. absolute hearing thresholds in Pascals and their corresponding SPL in decibels are indicated. To achieve them at frequencies of 1000 - 4000 Hz, a sound pressure of 2.10-5 Pa is sufficient. At 250 and 10,000 Hz an increase in pressure is required. Therefore, the curve of the absolute thresholds of hearing is convex upward.

Fig. 1.2.3.

In audiometry, measurement of relative auditory thresholds is accepted

(HL) from the zero isoline resulting from the average hearing thresholds of young healthy people. Hearing Level (HL) - hearing level. At the factory, the audiometers are specially tuned to the initial level of 0 dB (Fig. 1.2.3.) As the minimum auditory sensation at each frequency. The zero level of the audiometer does not correspond to the level of absolute hearing thresholds.

In fig. 1.2.4. the relative threshold isoline of hearing is presented in the form of a straight zero line and its ratio with absolute thresholds (dotted line). The lower dashed curve shows the maximum level of air conduction intensity on the audiometer, where the middle frequencies (1000 - 4000 Hz) have a greater sound range than low and high frequencies.

Fig. 1.2.4.

Sensation Level (SL) - individual threshold level of hearing of the patient from an audiometric zero at the appropriate frequency.

SPL, HL, and SL are European Community (EU) terminology.

Along with physical / objective / sound concepts, there are psychophysiological concepts corresponding to them: intensity - volume, frequency - pitch, spectrum - timbre and others that are associated with a person’s auditory sensations and have other units of measure (background, chalk, etc.).

Important properties of sound include phenomena of resonance, reflection, diffraction, and others. Resonance is the property of sound to cause sound vibrations of another object. Resonance matters in the mechanism of sound conduction in the outer, middle and inner ear. The natural oscillation frequency of the sound-conducting apparatus is about 1000 Hz. At this frequency, an increased sensitivity of the ear due to resonance is noted.

The ability of a sound wave to go around obstacles is called diffraction. Low sounds have better diffraction. The reflection of a sound wave from obstacles in an open atmosphere is an echo (in a forest, mountains), and indoors - a reverberation. As a result of the meeting in the room: the acting and reflected waves, their interaction occurs, which is called interference, while the sound is amplified or weakened.

The average duration of the acoustic signal that the human ear perceives is 0.001 s. The sound impression remains in the ear for 0.009-0.1 s. The latent period of the patient’s reaction depends on the frequency and intensity of the tone: for high tones, it is shorter and inversely proportional to the intensity.

The human ear is capable of perceiving sounds from 16 to 20,000 Hz. Oscillations with a frequency of less than 16 Hz belong to infrasounds, and with a frequency of more than 20,000 Hz - to ultrasounds. However, B. M. Sagalovich (1968) notes that a person can perceive sounds from 1 Hz to 225 000 Hz, so their division into audible and inaudible is somewhat arbitrary. Sounds comfortable for our ear (noise of the forest, rain, sea) are in the range of about 1000 Hz. Human hearing acuity is most pronounced at the age of 15-30 years. The range of frequencies perceived by the ear is divided into three parts: tones up to 500 Hz are called low-frequency, from 500 to 3000 Hz - mid-frequency from 3000 to 8000 Hz - high-frequency and above 8000 Hz - super-frequency. The area of ​​speech frequencies is located in the region of 500 - 4000 Hz.

The auditory system includes sound-conducting and sound-receiving sections. The sound-conducting apparatus includes the outer and middle ear, peri-and endolymph, the main membrane, the integumentary and Reiner membranes. Sound perception begins with the receptor cells of the organ of Corti and includes the auditory centers of various levels of the central nervous system.
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    The term “aanoeaoey? Iue aiia? Ao” iaicia? A? O ioieeoiaua e ampullary receptors of the ear labyrinth. Due to the special anatomical arrangement of the semicircular canals and sacs of the vestibule, as well as the presence of an auxiliary apparatus, the ampullar receptors respond to angular acceleration, and the otolith receptors respond to rectilinear ones. Intermediaries in the perception by receptor cells of corresponding accelerations in
    Otorhinolaryngology is a science and practical discipline about diseases of the ear, nose, pharynx and larynx (abbreviated as ENT). Given the applied nature of the manual, it is advisable to provide the main content - a description of the diseases - with information on the clinical anatomy, physiology and research methods of these organs. Since diseases of ENT organs are often interconnected with pathology nearby
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    A more accurate method is the study of hearing using tuning forks. Tuning forks emit pure tones, with the pitch (oscillation frequency) for each tuning fork being constant. In practice, tuning forks tuned to tone C (do) in different octaves are usually used, including tuning forks C ,, C, c, cv c2, c3, c4, c5. Hearing tests are usually performed by three (C128, C512, C2048 or C4096) or even two
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