The principle of hearing examination is open--the transmission of sound and hearing examination 1

Although the current pure tone hearing test in China is very common, do you really understand the hearing test?

Many people will ask the hearing test to do air conduction. Why do you still need a bone conduction test?

Why should pure tone audiometry be based on different frequencies to measure different intensity sounds?

What is the principle of hearing test?

Waiting for these, if you want to understand all the hearing tests, let us first understand and understand from the aspects of the generation and transmission of sound, the measurement of sound, the intensity of sound and the loudness.

1. What is the generation and spread of sound?

As a kind of wave, sound is generated by the vibration of matter or object to produce mechanical waves (ie, sound waves). Sound waves are transmitted by air, liquid or solid, and are perceived by human or animal hearing organs.

There are two ways in which the sound is picked up by the human ear:

1. Gas conduction: sound → air → tympanic membrane vibration → listening to small bone vibration → auditory nerve → nerve center → cerebral cortex auditory perception

2. Bone conduction: sound → air → skull, jaw, etc. → auditory nerve → nerve center → cerebral cortex auditory perception

2. Measurement of sound: frequency and decibel
Frequency: The number of times the audible wave source changes periodically, that is, the number of vibrations of the vocal wave source within 1 second. The unit of frequency is Hertz (Hz). Nature and humans may produce a wide range of sound frequencies, but not all sonic vibrations are heard by the human ear. The audible frequency of the human ear ranges from 20 Hz to 20,000 Hz. Generally speaking, the low frequency affects the fullness, thickness and strength of the sound, and the high frequency affects the brightness, clarity and transparency of the sound.

Decibel: The unit (dB) used to indicate the intensity of the sound. The sound is also accompanied by the propagation of energy. It is expressed in units of energy (the energy flow density of the acoustic wave) perpendicular to the direction of propagation of the sound wave per unit time. Physical instruments (such as sound level meters) to measure. Even 0 dB does not mean that there is no sound, which means that the sound pressure value that the normal human ear can just hear at 1 kHz is 20 uPa (A), which is recorded as 0 dB.