A study coming from University of Texas, Dallas has shown that noise pollution is more than just a nuisance. Researchers found that consistent loud noises hurt the brain’s ability to function, especially with regard to decoding speech.
Noise is defined as any unwanted sound – it can be a jack hammer incessantly drilling away on the roads outside your apartment on a busy city street: the sound of loud, irritating cell phone ringing, the low hum of a train, or monorail that is located near your domicile. It could even be the decibel-shattering music coming from that car next to you on your morning commute.
Increased urbanization has led to more sound pollution, and while scientists already figured out that this unwanted noise can lead to sleep deprivation, concentration issues, headaches, and irritability, UTD scientists now say it can even impair how our brain processes human speech in a quiet environment.
A paper published this week in Ear and Hearing suggests that noise-induced hearing loss can keep the brain from recognizing familiar speech sounds. About 15% of Americans between the ages of 20 and 69 suffer from this condition.
Consistent loud sounds damage the tiny hairs in our ears that act as receptors. Once they are damaged, they can’t grow back.
“As we have made machines and electronic devices more powerful, the potential to cause permanent damage has grown tremendously,” said Dr. Michael Kilgard, co-author and Margaret Fonde Jonsson Professor in the School of Behavioral and Brain Sciences. “Even the smaller MP3 players can reach volume levels that are highly damaging to the ear in a matter of minutes.”
Even emergency vehicles have had to turn up the volume to compete with urban noise pollution. They went from 110 decibels a few years ago to the siren on an emergency vehicle now being at 120 decibels.
Rats in the study with severe hearing loss were exposed to consistent loud noises, and the following was observed:
“. . .the auditory cortex, one of the main areas that processes sounds in the brain, is organized on a scale, like a piano. Neurons at one end of the cortex respond to low-frequency sounds, while other neurons at the opposite end react to higher frequencies.
In the group with severe hearing loss, less than one-third of the tested auditory cortex sites that normally respond to sound reacted to stimulation. In the sites that did respond, there were unusual patterns of activity. The neurons reacted slower, the sounds had to be louder and the neurons responded to frequency ranges narrower than normal. Additionally, the rats could not tell the speech sounds apart in a behavioral task they could successfully complete before the hearing loss.”