Creating natural
sound experiences
Today’s most advanced hearing aids are able to deliver better,
personalised sound without annoying artifacts, as Lise Henningsen explains
Natural sound: It’s all around
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us. The voices of our loved
ones; waves crashing and birds
singing, symphonies playing, traf c
passing by. But many people have a
hard time enjoying natural sound - or
any sound for that matter.
According to the National Institute
of Health (NIH), one in eight people
aged 12 years and older has hearing
loss in both ears. Twenty- ve per cent
of adults aged 65 to 75 and half of
adults aged 75 and older experience
disabling hearing loss. All told, it’s
estimated that about 26 million adults
in the US have suffered permanent
hearing damage, with estimates that a
further 28.8 million could bene t from
using hearing aids.
But for many, there’s a problem
with wearing hearing aids in that they
don’t sound natural. In fact, sound
quality and the “naturalness” of
sound remain among the most-cited
reasons people don’t pursue hearing
assistance, despite the great strides
in hearing aid innovation made over
the last decades.
Ironically, the unnaturalness of
hearing aid sound is, to a great extent,
the by-product of that innovation.
When hearing aids went digital, drastic
improvements in noise reduction and
advanced signal processing came at
a price.
In the beginning, hearing aids
were built to compensate for hearing
loss and make speech audible again.
Of course, the reality was - and
remains - that ambient noise and the
consequences of hearing loss are
variable and listener speci c.
Today, high end hearing aids are
intelligent. They can process and
separate out unwanted noise, like
background conversation in a coffee
shop, while simultaneously enhancing
nearby speech so the wearer can
better hear their companion. Really
good digital hearing aids can even
automatically adapt to different
listening environments so the wearer
doesn’t have to, and they eliminate
feedback that might have been
associated with analogue technology.
They do all this through advanced
digital signal processing, but
therein lies the rub, and the
reason for further innovation
in creating a more natural sound
experience for the millions of people
seeking it.
Unnatural sound
Taking an analogue sound wave,
converting it to a digital signal,
processing it, then re-converting it
back into a sound wave that the ear
can perceive, takes time - in most
cases 4 to 8 milliseconds. A signal is
passed through the input stage and
converted to digital numbers, passed
through a lter bank, which splits it
into various channels for processing,
for example to compensate for a
person’s unique hearing de ciencies
in one frequency range but not
another.
Finally, the digital signal again
needs to be converted from numbers
back to an analogue sound wave
at the output stage of the hearing
solution. Studies have shown that a
processing delay within that 4-to-8-
13 October 2020 www.newelectronics.co.uk
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