Why are you afraid of noise when you are deaf

We always think that deaf people can’t hear in a low voice. It’s better to speak louder, and the bigger the better. Actually not. Many deaf people are afraid of noise, even very afraid of noise.

Our hearing is limited. Just as the temperature of freezing water is set at 0 ℃, audiologists artificially set hearing level 0 (0dbhl) for several different frequencies that normal young people just can hear. People with normal hearing level 0 can barely hear. The conversation sound in quiet environment is about 60 listening level, which sounds soft and appropriate. If we shout in our ears, we will all be disgusted because the voice is too loud. We can’t stand the louder sound. Generally speaking, our tolerance limit will not exceed 140 listening levels.

From the 0 listening level that we just can hear to the maximum 140 listening level, it is the range that we can hear, which is called “dynamic range of hearing”. If there is hearing loss (deafness), the sound that just can be heard will not be level 0, but may be level 30, 60, 70 or more. If a deaf person’s average hearing loss (PTA) is 60 hearing level (which means 60 hearing level is the sound he just can hear, equivalent to our 0 hearing level) and if he also has 140 hearing level’s dynamic range of hearing, then the deaf person seems to be able to bear about 200 hearing level’s sound. In fact, not only can no one bear the sound with a hearing level of 200, but such a big sound does not exist in nature. The second assumption is totally wrong.

Although the low voice can’t be heard, most of the deaf, especially the patients with nervous deafness, can’t tolerate the loud voice better or worse than those with normal hearing. Don’t say 140, that is 130, 120, 110 hearing level, they also often hear “deafening”. This is because their auditory dynamic range is narrowed to varying degrees, sometimes even to less than 5 decibels, that is to say, reducing 5 decibels can’t hear, increasing 5 decibels can’t stand. Therefore, many deaf people are more afraid of noise than normal hearing people.

Fear of noise after deafness, the term is “rejuvenation” (reverberation) phenomenon. Rejuvenation is a pathological change accompanied by hearing loss. Its essence is the result of the maladjustment of inner and outer hair cells. How to understand rejuvenation? We can think of it as “auditory allergy” under certain conditions. Simply put: when the voice is doubled, the normal people’s listening feeling is doubled; when the voice is increased 10 times, 100 times, the normal hearing people will correspondingly increase 10 times, 100 times. This is not the case for the deaf who have been revived. When their voice is doubled, their listening sensation will be increased 10 times, 20 times or even 50 times. The overgrowth of auditory sensation (loudness) leads to the phenomenon of rejuvenation. Because of this, deaf patients with rejuvenation problems are particularly afraid of noise.