New research from the Science subjournal calls into question old ideas about how hearing works

The way we experience music and language is different
from what people have believed so far.
That's the conclusion
of a study by researchers at Linkping University in Sweden and Oregon Health and Science University in the United States.
The findings make it possible
to design better cochlear implants.

We are social animals
.
The voices of others are important to us, and our sense of hearing is meant to experience and distinguish between sound and human language
.
The sound that reaches the outer ear is transmitted through the ear drum to the spiral-shaped inner ear, also known as the cochlea
.
The sensory cells of hearing, the outer and inner hair cells, are located in the cochlea
.
Sound waves cause the "hairs" of internal hair cells to bend, sending signals through nerves to the brain, which interprets
the sounds we hear.

For the past 100 years, we've believed that each sensory cell has its own "optimal frequency" (a measure of the number of sound waves per second
).
Hair cells respond most strongly
to this frequency.
This idea means that the optimal frequency of 1000 hz of the feeling cells to respond much
weaker to sounds with slightly lower or higher frequencies.
It is also believed that all parts of the cochlea work
in the same way.
Now, however, a team of researchers has found that this is not the case for sensory cells that process sounds with frequencies below 1000 hertz (considered low-frequency sounds
).
The vowels in human language are in this area
.

"Our study shows that many cells in the inner ear respond
to low-frequency sounds simultaneously.
We believe that this makes it easier for people to experience low-frequency sounds because the brain receives information from many sensory cells at the same time," said
Anders Friedberg, a professor in the Department of Biomedical and Clinical Sciences at Linkping University.

Scientists believe that this structure of the auditory system makes our auditory system stronger
.
If some sensory cells are damaged, many others can still send nerve impulses
to the brain.

Not only are vowels in human language located in the low-frequency region: many of the sounds that make up music are also located in this region
.
For example, the frequency of the middle C on a piano is 262 Hz
.

These results can eventually have a significant impact on people with severe hearing impairments
.
The most successful treatment in this case is currently a cochlear implant, where electrodes are implanted into the cochlea
.

"The current design of cochlear implants is based on the assumption that each electrode can only stimulate nerves at specific frequencies, in some way trying to replicate the function of
our auditory system.
We suggest that changing the low-frequency stimulation method will be closer to the natural stimulus, and the user's hearing experience should be improved in this way," said
Anders Friedberg.

The researchers now plan to study how to apply their new knowledge to practice
.
One project they are working on involves a new way
to stimulate the low-frequency parts of the cochlea.

These results come from experiments on guinea pig cochlea, whose hearing is similar
to that of humans in low-frequency regions.
The study was funded
by the National Institutes of Health and the Swedish Research Council.

essay

Best frequencies and temporal delays are similar across the low-frequency regions of the guinea pig cochlea