Sound – Part 3
The phenomenon of resonance plays an important role in the conduction of sound, in which the sound wave of a vibrating object causes the vibratory movements of another (resonator).
The resonance can be sharp, if the natural oscillation period of the resonator coincides with the period of the acting force, and muffled, if the oscillation periods do not coincide. With a sharp resonance, the oscillations decay slowly, dull, quickly. It is important to note that the vibrations of the structures of the ear that conduct the sounds decay rapidly; This eliminates external sound distortion, so that a person can receive more and more sound signals quickly and steadily. Some structures of the cochlea have a sharp resonance, which helps to distinguish between two closely spaced frequencies. The main properties of the hearing analyzer. The main properties of the hearing analyzer include its ability to distinguish between the pitch (frequency concept) of sound, its volume (intensity concept) and the timbre, which includes the main tone and harmonics. As is common in classical physiological acoustics, the human ear perceives a band of sound frequencies from 16 to 20,000 Hz (12-24 to 18,000-24,000 Hz). The greater the amplitude of the sound, the better the audibility. However, up to a known limit, beyond which sound overload begins. Vibrations with a frequency of less than 16 Hz are called infrasound and above the upper limit of auditory perception (that is, more than 20,000 Hz) – ultrasound. Under normal conditions, the human ear does not pick up infrared and ultrasound, but with a special study these frequencies are also perceived, hearing gradually deteriorates with age. it moves towards the perception of low frequencies and the area of greatest sensitivity. So if at age 20-40 it is in the 3000 Hz region, then at age 60 and older it shifts to the 1000 Hz region. The upper and lower limits of hearing can change with disease. of the auditory organ, as a result of which the area of auditory perception is reduced. In children, the upper limit of sound perception reaches 22,000 Hz, in older people it is lower and usually does not exceed 10,000-15,000 Hz. In all mammals, the upper limit is higher than in humans: for For example, in dogs it reaches 38,000 Hz, in cats – 70,000 Hz, in bats – 200,000 Hz or more. As studies carried out in our country have shown, a person is capable of perceiving ultrasounds with a frequency of up to 200-225 kHz, but only with bone conduction.
+ The entire range of frequencies perceived by the human ear is divided into several parts: tones up to 500 Hz are called low frequency, 500 to 3000 Hz – medium frequency, 3000 to 8000 Hz – high frequency. Different parts of the range are perceived by the ear differently. It is most sensitive to sounds in the 1000-4000 Hz range, which is important for the perception of the human voice. The sensitivity (excitability) of the ear at frequencies below 1000 and above 4000 Hz is significantly reduced. Therefore, for a frequency of 10,000 Hz, the threshold sound intensity is 1000 times greater than for the optimal sensitivity zone of 1000-4000 Hz. The different sensitivity to low and high frequency sounds is largely due to to the resonant properties of the external auditory canal. The corresponding properties of the sensitive cells of the individual snail curls also play a role.
