Kitz Forum
Broadband Related => Telephony Wiring + Equipment => Topic started by: renluop on March 30, 2018, 12:54:33 PM
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Guys, this may be an odd one!
My sister-in-law has been increasingly deaf for years, has had a cochlear implant fitted a month or so ago. Her husband has to be careful as she now hears what he says. :lol:
More seriously though, she has found it a blessing, but we have noticed problems with communications by phone. We know it will improve, but I'd like to know, is there something like compression applied in the transmission caller to called, which causes her difficulty?
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If it's a mobile phone it may just need the volume to be turned down a bit.
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The bandwidth of standard landline voice circuit is limited to between about 300Hz and 3.4kHz, so it may be having some effect.
:)
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Is she able to put the phone on 'speakerphone'? Does that help?
A friend of mine has had an implant; apparently things get easier as the brain gets attuned to the changed sounds. :) :fingers:
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My query is about the tech side.She has a helpful family, so I shall not butt in unless asked. :)
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There is no audio compression applied; the bandwidth is just very limited. As tubaman has stated, the standard UK telephone audio pass-band is 300 to 3400 Hz.
Persons with normal hearing (whatever that might be!) will be able to recognise and understand a caller using just those frequencies. Perhaps your SIL could experiment by moving the ear-piece of the handset to various off-set locations around the ear and see if that aids the speech recognition?
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When an anologue (voice) signal is digitally encoded in a digital phone network, it is normally subjected to a ‘companding’ algorithm, which improves efficiency, allowing a lower bit rate. Based upon assumptions of human hearing perception, the audible artefacts caused by that compression/expansion will, in theory, be unnoticeable. For example, A-law encoding is common in North America and Japan, u-law in Europe.
https://en.m.wikipedia.org/wiki/Companding
I wonder if anybody has carried out the necessary research, to establish whether the assumptions about arteracts being unnoticeable to ‘normal’ perception also apply to cochlear implants?