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Prolonged Exposure to Loud Noise Alters Speech Processing

  • Jessica Berman

New research suggests exposure to loud sounds like emergency vehicle sirens... even high volume from an mp3 player... may be damaging the brain as well as the ears.

15 percent of Americans between the ages of 20 and 69 have some problem with noise induced hearing loss. And scientists know that loud noises can physically damage the hair cells in the ear that receive sound.

This new research suggests that hearing damage also could affect your brain's ability to process sounds into speech and conversation.

Scientists at the University of Texas at Dallas exposed rats to loud noises causing moderate and severe hearing loss.

Afterwards the scientists tested the parts of the rats brains that process sound, an area called the auditory cortex.

In the severely damaged rats, less than one third of the cortex responded to stimulation. And the areas that did, reacted slower.

The moderately damaged rats' brains also changed... reacting more slowly, and needing more stimulation than rats with normal hearing function.

This is important because, as the researchers point out in the journal Ear and Hearing, hearing is a complex process. They say the physical act of hearing is just the first step in a neural process your brain uses to turn sounds into understandable speech.

They also point out that once the hair cells of the ear are damaged, they don't grow back so the damage is irreversible.