Why is it that the sound of wearing a hearing aid is loud but I can't hear clearly?

What hearing aids debug low frequency gain should not be too large?

Let's take a look at the table below

The relationship between energy and intelligibility at different frequencies, as shown in the table:

As can be seen from the table, if the energy below 500HZ is removed, the loss of speech intelligibility is only 4%, the loss of nearly 50% of the energy, if the energy above 1000HZ is removed, 5% of the energy is lost, but the loss of speech intelligibility is 60%.

The up-diffusion masking characteristics of the sound determine that low-frequency sounds have more masking for high-frequency sounds. Therefore, in many hearing aids, the method of reducing the low frequency gain is used to reduce noise. In the language phonemes, the vowels are mostly distributed in the low frequencies, and the consonants are more distributed in the high frequencies, so the vowels are more than the consonants; the lower frequency of the vowels carries only a small amount of semantic information, and the higher the consonant frequency carries most of the information. Most of the severe and extremely severe deaf children are high frequency loss low frequency loss weight, the fitters in order to compensate for high frequency loss often take a desperate effort to increase the gain of high frequency, but for those who have no or little high frequency residual hearing, the high high frequency gain can not make the no longer existing hearing react. In turn, in order to allow the deaf to hear the sound, the low frequency gain is increased.

The vowels in Chinese are consonants, where most of the central frequencies in the Qing consonants are above 4KHz, and the sound intensity range in long-term conversational sound spectrum is between 5-40dBHL, averaging 25dB, so once the deaf person has more than 60dB hearing loss at more than 4000Hz, it is only possible to perceive high-frequency consonants when it can obtain at least 20dB or more high-frequency gain. It is difficult for non-frequency shifting hearing aids to produce a gain of 20dB at frequencies above 4KHz. After wearing hearing aids, most deaf people feel that the low frequency compensation is better and the high frequency compensation effect is not good, and the result is that the hearing aid has sufficient gain in the middle and low frequency bands and insufficient high frequency gain, resulting in the masking of the vowels on the consonants in the amplified sound. This is also the reason why many foreign studies have proved that when the patient's high-frequency hearing loss exceeds 60dB, the traditional hearing aid has no effect on the patient's speech discrimination but has a negative impact. Therefore, when adjusting the machine after hearing aid fitting and stage evaluation, in order to avoid the "upward masking" phenomenon affecting the clarity of severe and extremely severe deafness neurogenic deaf children, please be careful not to debug the low frequency gain of the hearing aid too large.