What is Noise-Induced Hearing Loss (NIHL)?

Noise-Induced Hearing Loss also known as NIHL

We are being bombarded by loud noises everyday. While we are being exposed to the environment filled with sounds and noises such as television, radio, household appliances, smartphones and traffic. Normally, these sounds are at safe level that don’t damage our hearing. But any sound can be harmful and be detrimental when they are too loud, even for a very brief of time or loud and long-lasting. Our sensitive inner ear structure (hair cells) can be damaged by these sounds and cause noise-induced hearing loss (NIHL).

How It Happens?

NIHL can be caused by a one-time exposure to an intense “impulse” sound, such as an explosion or firecracker, or by continuous exposure to loud sounds over an extended period of time, such as noise generated in a machine factory. Even your hobby and some recreational activities can put you at risk for NIHL such as listening to music at high volume, attending loud concert, or woodworking tools. If noise exposure is infrequent, hearing may recover after resting. But, chronic exposure to noise that is loud enough to cause ringing in the ears (often called tinnitus) can eventually lead to permanent noise-induced hearing loss (NIHL).

You may have a hard time to notice NIHL because it can take a longer time to develop unless you are exposed to impact and very high levels of noise (>130dBA), which then you may experience sudden hearing loss as a result of acoustic trauma. NIHL is 100% preventable; however, once acquired, it is permanent and irreversible. . Typically after a loud noise exposure, people may experience only temporary (hearing) threshold shift (TTS),  but at some point, the injury may become a permanent threshold shirt (PTS). You’ll be surprise for this type of hearing loss, regardless of the frequency of the noise that caused it, most of the hearing tests result suggest NIHL typically affects at higher frequency region in one or both ears, which usually begins audiometrically at 3000-6000 Hz without affecting the lower frequency region at the beginning of the stage.  If you are starting to aware that you have difficulty to understand what others’ trying to say, listen on the phone or need a louder volume than usual when you’re watching TV, you might have hearing loss.

Standard audiogram with speech banana overlay demonstrating a noise induced hearing loss

Picture 2: Sample audiogram of NIHL and its effect on speech banana. (Source: researchgate.net)

Can You Be Affected By NIHL?

People of all ages, including children, teens, young adults, and older people, can develop NIHL after long hours exposure to harmful noise. However, the most affected group are industrial and construction workers who constantly exposed to high level of machinery or construction noises at work without wearing any hearing protection device (HPD). According to OSHA Malaysia (2015), NIHL is the top ranked occupational health disease. Besides, recent studies had shown teenagers tends to develop hearing loss at early age due to prolonged music listening habit. As a parent you can prevent hearing loss to occur in your children and teach them healthy hearing habits for life. People of all ages can protect their hearing by just lowering the volume, moving away from the noise and wearing earplugs or other hearing protectors. Safe listening volume of general device is always below 80% of the overall volume.

How Loud Is Too Loud?

Sound is measured in a unit called decibels. It is safe to listen to sounds less than 80 decibels. To understand better, let us guide you through on these examples; a normal conversation between you and others is around 60 decibels while noise from motorcycle is around 95 decibels. Listening to music at maximum volume via headphone is around 105 decibels. Firecrackers, 140 decibels. So protect your ears this festive season! There is a recommended permissible noise level exposure in relative to time duration. A general rule of thumb is every increase of 3 decibels, it reduce half of the permissible time limit exposure of the noise.

Permissible exposure noise level in relation to time duration limit

Remember, always be alert to hazardous noises in the environment. If you are aware, keep your ears close with your hands or just simply move away from it. Your hearing needs you!