The sounds we hear in almost every environment are reflected by nearby objects, producing many delayed and distorted copies of the original sound, known as reverberation. Our brains are usually able to filter this out, allowing us to recognise the source of each sound regardless of the environment, to the extent that people with normal hearing rarely notice it at all. However, reverberation is known to cause severe difficulties for many people with hearing impairments, and for speech recognition algorithms such as those designed to assist those who cannot hear.
Despite the ubiquity of reverberation, the question of how the brain’s auditory system copes with reverberation has been largely unanswered. Recent research has observed that the effects of room reverberation seem to be partially removed from the neural responses to sounds in the auditory cortex. However, so far it has been largely unknown how the brain could ‘remove’ reverberation in this way.
A new paper from DPAG's King and Walker research groups has demonstrated, for the first time, how the brain may accomplish this ‘reverberation cancellation’. Their data shows that auditory cortical neurons adjust their filtering properties to adapt to changing acoustics of reverberant environments and reduce the effects of reverberation.