Written by Margaret Wei

Noise pollution, which is measured in decibels, is defined as any unwanted or disturbing sound that affects the health and well-being of humans and other organisms. Sounds that surpass 85 decibels are considered harmful, as they can damage ears. Noises that exceed this threshold are very prominent in our daily lives, including lawn mowers (90 decibels), subway trains (90 to 115 decibels), sirens (120 to 140 decibels), and concerts (110 to 120 decibels). Even nature can make noises that exceed 85 decibels, such as thunder (120 decibels). Long term exposure to these excessive noise sources have shown to cause nerve overstimulation which leads to not only ear damage, but also stress, poor concentration levels, communication and cognitive impairment, lack of sleep, tinnitus, and hearing loss. One of the more severe effects is setting off the body’s acute stress response, which raises pressure and heart rate, which can lead to cardiovascular disease. In addition, children are at the highest risk of the effects of noise pollution as the implications include impairments in memory, attention level, and reading skill, since their cognitive development is at its peak. 

The ears are highly responsive and never rests, even when asleep. This is because the ears are part of a “permanently open auditory system,” which means that, even when unconscious, sounds are still processed that are filtered and perceived by various areas of the brain. Due to its inability to shut down, noise pollution poses a great threat to the ears. To study the effects of noise pollution, Dr. Orfeu Buxton, a sleep expert at Harvard University, played different types of 10-second audio clips as volunteer subjects slept. Measuring the brainwaves of the subjects as the clips played, he discovered that the clips caused spiked patterns of neural activity. In contrast, when the clips were not playing, the brainwaves settled to a flatter pattern, indicating less brain activity. 

To test how hearing loss affected speech sound processing, researchers from UT Dallas scientists conducted a study that exposed rats to moderate or intense levels of noise for an hour. One group heard a high-frequency noise at 115 decibels inducing moderate hearing loss, and a second group heard a low-frequency noise at 124 decibels causing severe hearing loss. They recorded the rats’ auditory cortex neuronal response a month after the noise exposure. In the group with severe hearing loss, less than one-third of the auditory cortex sites reacted to stimulation, but the neurons reacted slower and responded to narrower frequency ranges. In the group with moderate hearing loss, a larger area of the auditory cortex responded to low-frequency sounds and neurons reacting to high frequencies needed more intense sound stimulation and responded slower. The results indicate that noise pollution affects everyone, regardless of age and species. Thus, a better understanding of the extent of environmental noise pollution is crucial in order to improve future studies in human health and environmental policies. 

Meanwhile, there are some things that individuals can do to reduce noise by turning off appliances more often and only switching on at certain times, lowering the volume on  televisions, avoiding playing unnecessary background noise. Also, one can set aside dedicated time for watching TV or listening to music. If loud noise is unavoidable, soundproofing the surroundings by adding insulation, rugs, and curtains may help muffle external sounds, and using ear protection is helpful to reduce the effects of noise pollution.

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