The cocktail party effect

Timothy C. Hain, MD Page last modified: June 18, 2009

People with hearing loss often compain of greater difficulty in understanding speech, when there are competing sounds sources such as other people talking in a restaurant or party, or loud music.

There are several reasons for this --

• People with hearing deficits may simply have less sound coming in, so they are less able to process out signal from noise
• People with hearing deficits may have frequency drop-outs in their hearing.
• They may be unable to use their "active equilizer system", or the outer hair cells (see OAE testing).
• If one ear is much worse than the other, they may lose their ability to compare input from each ear to localize a sound source and therebye select it out from noise. This sophisticated task is done by central comparison of timing of the same signal, across ears.

The cocktail party effect denotes the advantage that a listener gains from having two ears separated in space when separating a signal from auditory noise.

In humans, when the speaker and noise come from different locations, there can be an improvement of up to 18 dB. (Gatehouse, 1987; Saberi et al, 1991).

References:

• Gatehouse RW (1987). Further research on free field masking. JASA 82, S108
• Saberi and others. (1991). Free-field release from masking. JASA 90, 1355-1370