Cocktail party effect
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The cocktail party effect describes the ability to focus one's listening attention on a single talker among a mixture of conversations and background noises, ignoring other conversationsArons, B. (1992, July). [A Review of The Cocktail Party Effect.]. This effect reveals one of the surprising abilities of our auditory system, which enables us to talk in a noisy place.
The cocktail party phenomenon can occur both when we are paying attention to one of the sounds around us and when it is invoked by a stimulus which grabs our attention suddenly Moray, N. (1959) Attention in dichotic listening: Affective cues and the influence of instructions Quarterly Journal of Experimental Psychology. For example, when we are talking with our friend in a crowded party, we still can listen and understand what our friend says even if the place is very noisy, and can simultaneously ignore what another nearby person is saying. Then if someone over the other side of the party room calls out our name suddenly, we also notice that sound and respond to it immediately. The hearing reaches a noise suppression from 9 to 15 dB, i.e., the acoustic source, on which humans concentrate, seems to be three times louder than the ambient noise. A microphone recording in comparison will show the big difference.
The effect is an auditory version of the figure-ground phenomenon. Here, the figure is the sound one pays attention to, and the ground is the any other sounds ("the cocktail party").
Experiments and theoretical approaches
The effect was first described (and named) by Colin Cherry in 1953Cherry,E.C. (1953) Some experiments on the recognition of speech, with one and with two ears. Journal of Acoustic Society of America 25, 975--979.. Much of the early work in this area can be traced to problems faced by air traffic controllers in the early 1950's. At that time, controllers received messages from pilots over loudspeakers in the control tower. Hearing the intermixed voices of many pilots over a single loudspeaker made the controller's task very difficult.
Cherry (1953) conducted perception experiments in which subjects were asked to listen to two different messages from a single loudspeaker at the same time and try to separate them. His work reveals that our ability of separating sounds from background is based on the characteristics of the sounds such as gender of the speaker, direction from which the sound is coming, pitch, or the speaking speed.
In the 1950's, BroadbentBroadbent, D.E. (1954). The role of auditory localization in attention and memory span. Journal of Experimental Psychology, 47, 191-196. conducted dichotic listening experiments: subjects were asked to hear and separate different speech signals presented to each ear simultaneously (using headphones). From results of his experiment, he suggested that "our mind can be conceived as a radio receiving many channels at once": the brain separates incoming sound into channels based on physical characteristics (e.g. perceived location), and submits only certain subsignals for semantic analysis (deciphering meaning). In other words a kind of audio filter in our brain which selects which channel we should pay attention to from many kinds of sounds perceived. This is called Broadbent's filter theoryBroadbent, D. E. (1958). Perception and communication. New York:Pergamon.. There is some empirical evidence to support this theory, although it has been criticized by some (Norman, et al).
There are other theories, including those of Treisman (1960), and Deutsch and Deutsch (1963).
This phenomenon is still very much a subject of research, in humans as well as in computer implementations (when it is typically referred to as source separation or blind source separation). The neural mechanism in human brains is not yet fully clear.
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