一个健康人的耳朵能分辨出40万种不同的声音,足够感受精彩的外部世界。可是,在我们周围常能发现有些健康人表现出听力衰老的现象。如在看电视或接电话时,需要开大音量;在音乐厅、剧院等公共场所,声源距听者较远时,听起来常感到困难;在与人进行交谈时将头转向讲话者或扬声器,很 A healthy person’s ears can distinguish 400,000 different sounds, enough to feel the wonderful outside world. However, we can often find some healthy people around us to show the phenomenon of hearing loss. Such as when watching television or answering a phone call, it is necessary to turn on the loud volume; when the sound source is far away from the listener in public places such as a concert hall, a theater, etc., it often sounds difficult to talk to the speaker or the speaker Loudspeaker, very