Low and high frequency of hearing loss

< P style = "color:; font family: Arial, Verdana, sans serif;" >
General manifestations of HFD:

< P style = "color:; font family: Arial, Verdana, sans serif;" >
Performance 1, can’t hear others’ voices clearly, especially the female voice and children’s voice or smaller voice;

< P style = "color:; font family: Arial, Verdana, sans serif;" >
Performance 2: can’t hear the voice of two or more people talking clearly;

< P style = "color:; font family: Arial, Verdana, sans serif;" >
Third, the pronunciation, enunciation is not clear, there is a “big tongue” phenomenon, do not love to talk, do not love to communicate with everyone;

< P style = "color:; font family: Arial, Verdana, sans serif;" >
Fourth, the key voice with high frequency, such as bird call, insect call or telephone ring tone, can not be heard;

< P style = "color:; font family: Arial, Verdana, sans serif;" >
Performance 5. Listening to the voice is not natural and uncomfortable.

< P style = "color:; font family: Arial, Verdana, sans serif;" >
The most common high frequency sudden drop hearing loss is related to the anatomical parts of the ear.

< P style = "color:; font family: Arial, Verdana, sans serif;" >
Let’s first look at the following cases:

< P style = "color:; font family: Arial, Verdana, sans serif;" >
　　

< P style = "color:; font family: Arial, Verdana, sans serif;" >

< P style = "color:; font family: Arial, Verdana, sans serif;" >
1. The funnel-shaped structure of the outer ear and the curved “s” shaped ear canal have changed the acoustic physics of the outside world.

< P style = "color:; font family: Arial, Verdana, sans serif;" >
　　

< P style = "color:; font family: Arial, Verdana, sans serif;" >

< P style = "color:; font family: Arial, Verdana, sans serif;" >
As shown in the figure above, the change of sound gain of human auricle and ear canal for different frequency segments can be seen: the ear canal has the largest sound gain in the range of frequency 2khz-4khz. The results show that the hearing loss caused by noise is often located in the frequency range of twice the noise frequency, industrial noise is relatively constant in the low if range, and the natural resonance peak of the external auditory canal is 2khz-4khz, so it is most likely to cause hearing loss in the frequency range of 4khz-6khz. This is why noise induced hearing loss usually starts from about 4kHz at first, and gradually affects the better frequency.

< P style = "color:; font family: Arial, Verdana, sans serif;" >
2. Spiral structure of cochlea

< P style = "color:; font family: Arial, Verdana, sans serif;" >
　　

< P style = "color:; font family: Arial, Verdana, sans serif;" >

< P style = "color:; font family: Arial, Verdana, sans serif;" >
Sound is transmitted from the external auditory canal through the ossicular chain to the vestibular window of the internal ear. The shearing motion of the basement membrane suspended in the cochlea causes the change of the hair cell potential on it, and then it is transmitted to the cerebral cortex to feel sound.

< P style = "color:; font family: Arial, Verdana, sans serif;" >
　　

< P style = "color:; font family: Arial, Verdana, sans serif;" >

< P style = "color:; font family: Arial, Verdana, sans serif;" >
The structure of the cochlea is similar to that of the snail, which is about 2.5-2.75 turns. The propagation mode of sound wave on the basement membrane is based on the traveling wave theory in physics. The maximum amplitude of the basement membrane is related to the frequency of the sound wave, that is, each frequency of the sound wave has a corresponding maximum amplitude at different positions on the basement membrane: the maximum amplitude caused by high frequency sound is near the vestibular window at the bottom of the cochlea, the maximum amplitude at the low frequency is near the top of the cochlea, and the resonance occurs in the middle part of the intermediate frequency. Therefore, the transmission of sound from high frequency to low frequency requires the vibration of the basement membrane around the bottom, that is, the basement membrane at high frequency is relatively easy to fatigue. At the same time, the hair cells of the basal membrane around the cochlea contain lower antioxidant enzymes than the hair cells at the top. Therefore, the hearing loss of the aminoglycoside antibiotics (gentamicin, kanamycin, streptomycin, etc.) in the ototoxic drugs is a sudden drop type hearing curve.

< P style = "color:; font family: Arial, Verdana, sans serif;" >
3. Audio distribution of auditory nerve

< P style = "color:; font family: Arial, Verdana, sans serif;" >
　　

< P style = "color:; font family: Arial, Verdana, sans serif;" >

< P style = "color:; font family: Arial, Verdana, sans serif;" >
The distribution of the auditory nerve is in the same line with the spiral structure of the basilar membrane of the cochlea. The changes of physical and chemical environment, such as trauma, ischemia and hypoxia, herpes virus, affect the high frequency firstly.

< P style = "color:; font family: Arial, Verdana, sans serif;" >
Jinghao hearing aid reminder: hearing aid wearing requires professional “matching”, so it is very important to choose a professional hearing aid matching center and a hearing aid tester! If you have any hearing problems, you can call Jinghao for consultation, or come to the matching center for experience. Hearing aid free consultation Tel.: + 86-18566295705

< P style = "color:; font family: Arial, Verdana, sans serif;" >