“…The 2 main reasons for this difficulty are the restricted frequency range transmitted through conventional telephones (300Y3,400 Hz), which thereby limits the high-frequency content of speech (4), and the digital audio signal compression of the telephone switchboard. Users of hearing aids may face additional problems, such as feedback or unwanted noise, when their device is coupled to the telephone, either directly or with the use of various telephone improvement devices or amplifiers (4). Hearing-impaired individuals therefore often favor nonverbal communication tools, such as surface mail, fax, short messages (sms), e-mail, teletype writer, or Internet chatting (8,9).…”