Why do hearing aids need binaural fitting?

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Hearing aids can help patients to make use of residual hearing and compensate for lost hearing. As a rehabilitation tool, first of all, it is necessary to hear more clearly, then it is necessary to reduce noise, gain, balance function, etc., to protect residual hearing, slow down the time of hearing loss, and better communicate with others.

From the physiological point of view, the human body is not a symmetrical structure, and the hearing of both ears will be different, especially when both ears are hearing loss, the degree of damage is often different. Is that all I need to do is to have a hearing aid for one ear? Of course not. Let Xiaobian tell you the advantages of binaural fitting.

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Location and noise reduction of binaural sound source

1. Sound source location

Sound source localization is the auditory system’s judgment of the position of the vocal object. It includes horizontal and vertical sound source localization as well as the recognition of the distance from the listener. The balance of binaural hearing is one of the decisive factors for the localization ability of human sound source. Just as it is impossible to judge the distance of an object when observing it with one eye, it is also impossible to judge the position of the sound source with one ear hearing. So if the hearing damage of two ears is different, and only one side of the serious ears is equipped with hearing aids, the sound from any direction will be heard by the side with better hearing threshold, so the direction of the sound source cannot be determined.

2. Noise suppression

The auditory system is a good noise reduction system. The signal-to-noise ratio of the signal received by both ears is higher than that of the single ear, that is to say, both ears can reduce the noise more effectively than that of the single ear, and hear more clearly in the noise. When two ears receive the same signal, there will be a small time difference and phase difference. The brain can use these differences to identify the desired sound and ignore the noise.

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Binaural interaction

1. Integration effect

The sound signal from the two ears will be transmitted to the auditory center through the two auditory nerves, and the corresponding response will be made after the signal is integrated by the two cerebral cortex. The results show that the gain of binaural hearing is 3 dB more than that of single hearing. Because the wearing of both ears can improve the integration effect, especially reduce the energy integration of low-frequency sound, and reduce the overall output gain of the hearing aid, so the shell or ear mold of the hearing aid can be made short and loose, and the air hole can be increased, leaving as much space as possible for the inner part of the ear canal, so as to reduce the trouble caused by the ear blocking effect. This kind of integration and accumulation effect is more important for patients with binaural poisoning and extreme hearing impairment.

2. Auditory fusion

In nature, thousands of sound sources produce sounds that linger around people. Different kinds of sounds have different frequencies and intensities. These chaotic sounds are transmitted to both ears from different directions. The frequencies and intensities of the sounds heard in each ear are different. Through the auditory fusion effect, different sounds can be effectively integrated to both ears, so that they can be fused into a sound, improving the sound quality Stereo and sound quality.

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Avoiding head shadow effect and hearing deprivation

1. Avoid head shadow effect

The sound intensity of the two ears is different because of the different position of the sound source. When the sound is emitted from the left side, the sound heard in the left ear is significantly larger than that heard in the right ear. This phenomenon is the head image effect, which is caused by the barrier effect of the head.

If the hearing loss of a patient’s ears is asymmetric, when the sound comes from the direction of one ear with poor hearing, the ear with good hearing will face the sound source. Similarly, if both ears have hearing loss (symmetrical or asymmetrical), and only one ear is selected to wear when the hearing aid is selected, this phenomenon also exists. Because when the sound source comes from the other ear, the head can block and attenuate the transmission of sound wave, especially for high frequency sound higher than 2000Hz, the attenuation can reach 10-17db. Therefore, the definition of hearing aids will be greatly reduced. There are quite a number of patients with unilateral selection who are very difficult to listen to the sound from the side ear, and tend to turn the ear of the hearing aid to the other side. If the patient chooses to wear both ears, it will solve the head shadow effect, and there will be no embarrassment of listening to the voice with one ear, and can easily listen to the voice from multiple directions.

2. Avoid hearing deprivation

Hearing deprivation refers to the long-term acquisition of compensated hearing in one ear by patients with bilateral symmetrical hearing loss, and the speech recognition rate of uncompensated ears will gradually decrease with time. This phenomenon is related to the long-term asymmetric sound stimulation and unequal input of information. When one ear of the patient receives hearing aid, it can obtain relatively more sound information, while the non hearing aid ear can not receive sufficient sound stimulation, and the signal transmitted from the cochlea to the central auditory system is weak, so it is suppressed by the signal transmitted from the hearing aid. Over time, the brain seems to give up processing the information transmitted from the non hearing aid ear, resulting in the auditory deprivation effect. The speech recognition rate will be restored to a certain extent, some of which can even be restored to the initial level after hearing deprivation has been compensated for a period of time.

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When a lot of patients are fitting hearing aids (both ears have different degrees of hearing loss), they often put hearing aids on one ear, instead of carrying out double ear fitting, which may be due to price, psychological discomfort and other reasons. When you see the importance of double ear fitting now, you should pay more attention to hearing rehabilitation and ear health Ah, Jinghao has a large number of audiologists, who can solve all kinds of listening problems for you. Please call or come to the store directly.

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