My wife is hearing impaired and so has great difficulty using a
telephone. Unlike many whose hearing loss is caused by exposure to loud
sounds, her impairment affects the midrange rather than the high
frequencies. Above 5kHz her hearing is only about 5dB down from
baseline...but between 250Hz and 3kHz her hearing is over 70 dB down.

Unfortunately, most of the telephone hardware marketed for hearing
impaired users addresses high frequencies exclusively, or just provides
a global volume boost. In my wife's case, a high frequency boost is
pointless, and a global volume boost can't make enough of an
improvement over her midband attenuation before the upper frequencies
clip or become painfully loud.

So I figured a solution could be just a simple one- or two-band
parametric equalizer tied in to her telephone, so she could dial in a
reciprocal curve to her hearing loss and boost only those frequencies
that are severely attenuated for her.

Question is: how do I connect that equalizer to conventional phone
hardware? I suspect it might involve a hybrid coupler from Gentner or
JK Audio, but it's not immediately obvious to me how to interface the
phone & EQ. Plus I don't want to reinvent the wheel if there's
something already out there that addresses a similar problem.

Any ideas or suggestions? Thanks.

Roscoe East wrote:
My wife is hearing impaired and so has great difficulty using a
telephone. Unlike many whose hearing loss is caused by exposure to
loud
sounds, her impairment affects the midrange rather than the high
frequencies. Above 5kHz her hearing is only about 5dB down from
baseline...but between 250Hz and 3kHz her hearing is over 70 dB down.

Unfortunately, most of the telephone hardware marketed for hearing
impaired users addresses high frequencies exclusively, or just
provides
a global volume boost. In my wife's case, a high frequency boost is
pointless, and a global volume boost can't make enough of an
improvement over her midband attenuation before the upper frequencies
clip or become painfully loud.

So I figured a solution could be just a simple one- or two-band
parametric equalizer tied in to her telephone, so she could dial in a
reciprocal curve to her hearing loss and boost only those frequencies
that are severely attenuated for her.

Question is: how do I connect that equalizer to conventional phone
hardware? I suspect it might involve a hybrid coupler from Gentner or
JK Audio, but it's not immediately obvious to me how to interface the
phone & EQ. Plus I don't want to reinvent the wheel if there's
something already out there that addresses a similar problem.

Any ideas or suggestions? Thanks.

Roscoe East wrote:
My wife is hearing impaired and so has great difficulty using a
telephone. Unlike many whose hearing loss is caused by exposure to
loud
sounds, her impairment affects the midrange rather than the high
frequencies. Above 5kHz her hearing is only about 5dB down from
baseline...but between 250Hz and 3kHz her hearing is over 70 dB down.


Any ideas or suggestions? Thanks.

I don't have a solution because the very frequencies that she cannot
hear are the ones that are used in teleonone transmission (200 hz to
3kHz)

A parqametric won't bring anything up enough to make a difference.

About the only thing that could possibly help would be some form of
pitch shifter which would sample the signal and move it a couple of
octaves.

Anybody else have an idea?

Richard Kuschel

wrote:
Roscoe East wrote:
My wife is hearing impaired and so has great difficulty using a
telephone. Unlike many whose hearing loss is caused by exposure to
loud
sounds, her impairment affects the midrange rather than the high
frequencies. Above 5kHz her hearing is only about 5dB down from
baseline...but between 250Hz and 3kHz her hearing is over 70 dB
down.


Any ideas or suggestions? Thanks.

I don't have a solution because the very frequencies that she cannot
hear are the ones that are used in teleonone transmission (200 hz to
3kHz)

A parqametric won't bring anything up enough to make a difference.

About the only thing that could possibly help would be some form of
pitch shifter which would sample the signal and move it a couple of
octaves.

Anybody else have an idea?

Richard Kuschel

Right, nothing much over 3 kHz comes out of a standard phone line....

A graphic or parametric EQ can shape the frequencies within that range
followed by limiting/clipping that can reduce the dynamic range.

You might try a gradually tilted rising response across the 300 to 3
kHz range followed by moderate clipping.

Mark

"Roscoe East" wrote ...
My wife is hearing impaired and so has great difficulty using a
telephone. Unlike many whose hearing loss is caused by exposure to
loud
sounds, her impairment affects the midrange rather than the high
frequencies. Above 5kHz her hearing is only about 5dB down from
baseline...but between 250Hz and 3kHz her hearing is over 70 dB down.

But 300Hz to 3KHz is exactly the nominal bandpass for telephone
service. Something that bosts telephone volume uniformely would
effectively work only in that bandpass because that is pretty much
all that is there.

Doesn't her hearing aid do this for her?

Question is: how do I connect that equalizer to conventional phone
hardware? I suspect it might involve a hybrid coupler from Gentner or
JK Audio, but it's not immediately obvious to me how to interface the
phone & EQ. Plus I don't want to reinvent the wheel if there's
something already out there that addresses a similar problem.

There are four wires going to the handset. Two for the microphone,
and the other two for the earphone. You could physically intercept
the pair that goes to the headphone and run it through almost any
audio equipment.

Lots of pro audio equipment would likely drive the earphone to
"normal" levels. But if you need extra gain, you could add a small
power amp (just a few watts) and drive it as high as the transducer
will allow.

Richard Crowley wrote:
"Roscoe East" wrote ...
My wife is hearing impaired and so has great difficulty using a
telephone. Unlike many whose hearing loss is caused by exposure to
loud
sounds, her impairment affects the midrange rather than the high
frequencies. Above 5kHz her hearing is only about 5dB down from
baseline...but between 250Hz and 3kHz her hearing is over 70 dB
down.

But 300Hz to 3KHz is exactly the nominal bandpass for telephone
service. Something that bosts telephone volume uniformely would
effectively work only in that bandpass because that is pretty much
all that is there.

Except that it doesn't work in practice. We've tried a couple of the
global volume boost phones & they don't do anything useful for her. We
haven't bothered trying the high frequency only boost phones because it
seems pointless. Then again, if telephone bandwidth only goes to 3kHz,
exactly what "high frequencies" could they be referring to?


Doesn't her hearing aid do this for her?


Sadly, no. Don't get me started: $5,000 for a pair of allegedly
"state-of-the-art" CIC aids, and they've been back in the shop at least
twice a year for the last 4 years. Multiband compression/expansion
algorithms with sophisticated noise-discrimination capabilities, ya
right. Bite me. Worthless pieces of crap. Oops, sorry, I've digressed.

Was hoping someone had actual experience with the type of hardware I
might try.

Except that it doesn't work in practice. We've tried a couple of the
global volume boost phones & they don't do anything useful for her.
We
haven't bothered trying the high frequency only boost phones because
it
seems pointless. Then again, if telephone bandwidth only goes to
3kHz,
exactly what "high frequencies" could they be referring to?



3kHz is "high freq" relative to 300 Hz.

The range from 1kHz to 3 kHz is important for articulation.

Like I said, try to create a rising response from 300 to 3kHz i.e. 6 dB
per octave is a good start.

i.e.
300 = 0 dB
600 = +6dB
1200= +12 dB
2400 = +18 dB
300 = +20 dB

then you can add flat gain to that as needed

and some clipping after that may help

Mark