In this project, Dr Torsten Marquardt at University College London seeks to develop a new and more sensitive test of how damage to outer hair cells affects hearing.
Project start date: September 2020
Project end date: April 2023
Read about the project outcomes here.
About the project
In the inner ear, outer hair cells change their shape in response to sound, becoming longer (expanding) or shorter (contracting). Their movement enhances quiet sound signals, acting like an amplifier to make the signal stronger for our hearing brain. These cells are very fragile and loud noise, specific drugs and ageing can damage them, causing hearing loss.
We can detect the movement of outer hair cells in respond to sounds, because it generates an echo, known as an ‘otoacoustic emission’, which can be detected by a microphone positioned in the ear canal. A specialised kind of hearing test is used to capture these otoacustic emissions. If two simultaneous tones (at different pitches) are played to a listener, the echoes produced by the outer hair cells in response to those sounds are called ‘distortion products’. It’s these distortion products that give an indication of how well the outer hair cells are working.
This project will investigate a new way of combining these distortion products to develop a new and more sensitive test of how damage to outer hair cells affects hearing.
How it works
The slow changes in outer hair cell length are thought to underlie how the inner ear maintains its exquisite sensitivity to sound, by ensuring that the inner ear is always in the optimal state to detect the widest range of sounds. The researchers will use a new method to measure these changes using an animal model.
The length changes and their timing will be compared with simultaneously recorded ‘otoacoustic emissions’. If they match, this will show that the new diagnostic method truly reflects the ability of the inner ear to maintain its sensitivity to sound, even when the environment around it changes.
How will this research benefit people at risk to hearing loss?
The new measuring technique may form the basis of the first clinical test that can non-invasively detect problems with the inner ear’s ability to control its sensitivity. This will allow audiologists to more specifically diagnose the cause of a person’s hearing loss and choose the best treatment.
What we’ve learned so far
This project showed that a new type of hearing test, based on otoacoustic emissions, is reliable, including in humans. It provided new insight into how the inner ear regulates its sensitivity, highlighting the need for further research.
About the researcher
Dr Torsten Marquardt is Associate Professor in Auditory Biophysics at University College London Ear Institute. He was awarded an RNID Discovery Research Grant for this project in 2020.
I am immensely grateful to RNID for my Discovery Research Grant to support the development of new diagnostic tests that will help to evaluate the suitability of new treatments for individual patients. RNID also funds one of my PhD students, who will develop technology that will distribute these treatments evenly throughout the cochlea … RNID’s PhD studentships ensure that the UK remains a strong contributor to global hearing research.
