：聴覚損失

アメリカで現在、Hearing Loss聴覚損失を患う人々が急増しているという。

More than 28 million Americans have some degree of hearing loss, a number that could reach 78 million by 2030.

記事中、耳の内部構造の一角である、繊毛細胞をピアノの鍵盤にたとえた箇所は、強く鮮明な印象を残す。単純に小さい音が聞こえないのではない、聞きづらい音素のようなものがあるのだ。

Most common types of hearing loss occur at the higher frequencies and are caused by damage to hair cells. Slattery describes the cochlea as "a piano, with 15,000 keys rather than 88." Different parts of the cochlea process different frequencies of sound, so when you have hearing loss at a certain frequency, it's as if that part of the keyboard is not functioning.

Source:A Little Bit Louder, Please By David Noonan Newsweek June 6 issue