Cocktail Party Ear: You Hear What You Want to Hear

Youre at a crowded fete with lots of noise, the band is playing and the noise level keeps going up with each round of drinks. Youre swimming in noise. Yet, you can focus on a single voice and carry on a conversation despite the din. How?

Conventional Wisdom

You hear in stereo. Because the ears at set apart from each other, sound waves reach each ear at slightly different times. This difference in sound recognition between ears is what enables us to determine the direction of the sound, also known as directionality.

The brain, through experience, is able to calculate the direction of the sound instantly.

But wait. If the ability to focus on a single voice within a lot of chatter and clatter is based on our ability to determine sources of sound within the room, how do we explain the ability to focus on a telephone call while the party is in full swing. You can do it, thanks to that amazing brain of yours.

New Views

Researchers now suggest that were able to maintain focus on our little group, or quiet conversation, by differentiating sound by pitch. The brain focuses on the pitch the sound quality of important conversations while dismissing party background noise as unimportant. These sounds, while heard and processed, dont take on importance within the hearing portion of the brain.

Dr. Holger Schulze, a neuroscientist at the Leibniz-Institute for Neurobiology in Germany, a lead researcher on the phenomenon of cocktail party ear, stated, It has been known for 20 or 30 years that it is possible without directional information to do the job [focus on a single conversation while blocking out unnecessary noise] but we didnt know how it [the process] works, where in the brain this happens. Now we know its in one small area of the auditory cortex. FYI, the auditory cortex is where electrical impulses produced by sound in the environment are processed in the brain.

Researchers now believe that different noises and voices are arranged in a circle in the auditory cortex.

Within a circular map you can connect each region with all other regions equally well," Schulze told LiveScience. "This is important if you want one region to be able to inhibit all other regions equally well. If it [the sound-sorting process] was linear, you could only inhibit your neighbors."

One area sends neurotransmitters to other areas to say, ‘Stop listening,’" Schulze said. "But there must be some residual activity left so that if you hear something that catches your attention you can selectively switch focus."

In other words, the brain prioritizes all of these different sounds, focusing on the individual with whom youre speaking while ignoring the less important noise, or at least relegating it in importance. However, a small portion of the brain keeps track of important incoming so when youre asked a question, one part of your auditory cortex can process an answer while relegating other noises to lower priority status.

Though we can distinguish individual voices without knowing where they are coming from, if we have directional information this process is even easier. Both the pitch-sorting mechanism and directional sorting are usually going on simultaneously, Schulze concluded.

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