When are audio levels harmful to Ears

The human ear is exposed to a myriad of sounds (audio) at each day. Whether one is working at industrial plants with heavy machinery, travelling through noisy highways on a motorcycle, doing simple DIY projects at home with power drills, or even listening to an iPod, there is always a risk of losing one’s ability to detect sound.

What is Noise-Induced Hearing Loss (NIHL)?

While presbycusis – the loss of hearing due to changes to one’s inner ear – is a natural process associated with aging, NIHL is the result of damage to the sensitive structures of the inner ear caused by either a sudden loud noise such as an explosion, or regular exposure to excessive noises over a period of time.

These harmful noises will cause injuries to the microscopic hair cells inside the cochlea, which respond to mechanical sound vibrations by sending an electrical signal to the auditory nerve. Over time, the hair cell’s stereocilia will get damaged or broken by pressure, which results in deafness.

A person with NIHL may have trouble understanding speech because the louder, lower frequency vowels will be audible but not the softer, higher frequency consonants; hence the speech would end up sounding muffled. Tinnitus, or a buzzing in the ears, is also a common symptom of NIHL.

Types of Harmful Sounds

The average human ear can pick up sounds from 0 decibels (dB) onwards, and sounds above 85 dB are considered harmful to the ear. Most people might not be aware that many everyday sounds fall under this category, including the following:

Listening to music on earphones at a medium volume can generate sound pressure up to a level of 100 dB, which is loud enough to cause permanent damage after just 15 minutes per day. Rock concerts are also hazardous to hearing, measuring at approximately 120 dB.

A bulldozer which is idling can reach up to 80 dB, as can lawn mowers and leaf blowers. According to the United States’ National Institute for Occupational Safety and Health, exposure to these noises for a typical work day of eight hours can be harmful to the ears.

Busy city traffic registers audio levels of up to 85 dB, so if one lives near the highway, it is a good idea to erect barricades to minimise the noise.

Power tools like pneumatic drills go up to 140 dB, which is around the same level reached by gunshots or a clap of thunder.