How do sounds combine in inner ear?

Thread Starter


Joined Jun 1, 2021
I'm reading this answer on Bose's Sleepbuds product page, it says:
Masking works because of the way different sounds combine in our inner ears; if they have the right match of frequencies and the masking sound is just enough louder than the disturbing sound, the inner ear and brain cannot detect the disturbing sound.
Is there any place where I can find more information about how different sounds combine in inner ear?


Joined Aug 27, 2009
The mechanical vibrations of the organ of Corti had been analyzed by engineers since the 1940s. Their analysis was able to explain the frequency selectivity originally measured by von Bekesy in cochlea obtained from cadaver ears. It was known at the time that the measured frequency selectivity and the frequency selectivity computed from the engineering analysis did not approach the frequency selectivity of the human hearing or the frequency selectivity that could be measured from individual nerve fibers. Shortly after WW2 an American astrophysicist who had worked on radar during the war suggested that the frequency selectivity of the cochlea could be enhanced if a source of mechanical energy were present in the cochlea. His suggestion was largely ignored until several engineering groups in the late 70s rediscovered the potential benefits of this hypothetical energy source. They were forced to consider the possible existence of this “cochlear amplifier” when improved measures from living (as opposed to dead) ears revealed that the mechanical frequency selectivity in the living ear began to approach that of human hearing. The concept that a source of mechanical energy exists in the cochlea appeared validated when in the late 70s it was discovered that sound is produced by the inner ear. These sounds can be measured by placing a sensitive microphone in the ear canal. They were called otoacoustic emissions and they are now routinely measured in the clinic to assess hearing. Their discovery was amazing for sensory physiology because it was equivalent to finding that light comes out of the eye (which has never been observed). Within five years it was discovered that the outer hair cell could be made to elongate and shorten by electrical stimulation. The function of the outer hair cell in hearing is now perceived as that of a cochlear amplifier that refines the sensitivity and frequency selectivity of the mechanical vibrations of the cochlea.