Ear’s ‘power steering’ helps decode quiet soundsApril 22nd, 2009 - 1:42 pm ICT by ANI
Washington, Apr 22 (ANI): Ever wondered how you could hear those whispers while gossiping with friends in class? Well, scientists have now found that a nano motor of sorts in the ear makes us comprehend quiet sounds.
Human ears have bundles of tiny, hair-like tubes atop “hair cells” in the ear, which move back and forth and act like miniature ‘flexoelectric’ motors to amplify sound, according to Utah and Texas researchers.
Working like a power steering system of a car, the nanoscale motors magnify quiet sounds.
“We are reporting discovery of a new nanoscale motor in the ear. The ear has a mechanical amplifier in it that uses electrical power to do mechanical amplification,” said Richard Rabbitt, the study’s principal author and a professor and chair of bioengineering at the University of Utah College of Engineering.
He added: “It’s like a car’s power steering system. You turn the wheel and mechanical power is added. Here, the incoming sound is like your hand turning the wheel, but to drive, you need to add power to it. These hair bundles add power to the sound. If you did not have this mechanism, you would need a powerful hearing aid.”
Also, the researchers speculated that flexoelectrical conversion of electricity into mechanical work might also be involved in processes such as memory formation and food digestion.
In an earlier research, other researchers indicated that hair cells within the cochlea of the inner ear could “dance” - elongate and contract - to help amplify sounds.
But, in the current study, scientists have shown that sounds also may be amplified by the back-and-forth flexing or “dancing” of “stereocilia”- the 50 to 300 hair-like nanotubes projecting from the top of each hair cell.
Such flexing converts an electric signal generated by incoming sound into mechanical work - namely, more flexing of the stereocilia - which in turn amplifies the sound by what is known as a flexoelectric effect.
“Dancing hairs help you hear,” said Katie Breneman, the first author of the study.
The study “suggests sensory cells in the ear are compelled to move when they hear sounds, just like a music aficionado might dance at a concert. In this case, however, they’ll dance in response to sounds as miniscule as the sound of your own blood flow pulsating in your ear,” she added.
And in an unpublished upcoming study, researchers have found evidence that the hair cells themselves - like the stereocilia bundles atop those cells - also amplify sound by getting longer and shorter due to flexoelectricity.According to estimates, the combined flexoelectric amplification - by both hair cells and the hair-like stereocilia atop hair cells - could make humans hear the quietest 35 to 40 decibels of their range of hearing.
The researchers claimed that the flexoelectric amplifiers are needed to hear sounds quieter than the level of comfortable conversation.
“The beauty of the amplifier is that it allows you to hear very quiet sounds,” said a co-author of the study.
Rabbit says that because hair cells die as people age, older people often “need a hearing aid because amplification by the hair cells is not working.”
The new study is published in PLoS ONE, a journal published by the Public Library of Science. (ANI)
- How does brain hear quietest sounds, notice head motions? - Feb 15, 2010
- Invisible infrared light could soon activate heart, ear cells - Mar 28, 2011
- Discovery of ion channel upturns age-old model of ear - Apr 24, 2009
- Function of novel molecule that underlies human deafness revealed - Jan 22, 2011
- Dancing hair cells are key to humans acute hearing: Study - May 08, 2008
- How loss of hearing occurs with age - Oct 15, 2010
- Inner ear can 'store' recent sounds: Study - Apr 06, 2011
- New hope for restoring hearing loss in adults - Aug 28, 2010
- Role of motor protein in hearing loss revealed - Mar 07, 2011
- Quantum mechanics could tell us 'how long a tuning fork rings' - Mar 09, 2011
- Study on frogs and fish sheds light on human hearing - Mar 20, 2011
- Cranberry juice better at fighting bugs - Oct 30, 2011
- Old theory could help in noise protection - Dec 04, 2011
- Motorcycle helmets could make you hard of hearing - Jul 31, 2011
- Recipe for making sensory hair cells from stem cells found - May 14, 2010
Tags: cochlea, conversion of electricity, earlier research, electric signal, food digestion, hair bundles, hair cell, hair cells, human ears, incoming sound, inner ear, mechanical power, mechanical work, memory formation, nanoscale, principal author, rabbitt, texas researchers, tiny hair, utah college