噪音引起的听力损失，简称 NIHL

我们每天都在遭受噪音的轰炸。周围充满了来自电视、收音机、家用电器、智能手机和交通的声音。通常，这些声音的音量在安全范围内，不会对我们的听力造成伤害。然而，任何声音在过于响亮的情况下都会变得有害，尤其是当声音持续时间较长或非常短暂时。我们敏感的内耳结构（毛细胞）可能会因这些声音而受损，从而导致噪音引起的听力损失（NIHL）。

How Does it Happen?

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, 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 concerts, or using woodworking tools. If noise exposure is infrequent, hearing may recover after resting. But, chronic noise exposure 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 noticing NIHL because it can take a longer time to develop unless you are exposed to impact and very high levels of noise (> 130dba), at 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 shift (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 become aware that you have difficulty understanding what others’ trying to say, listening on the phone or need a louder volume than usual when you’re watching TV, you might have hearing loss.

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

谁可能受到 NIHL 的影响？

People of all ages, including children, teens, young adults, and older people, can develop NIHL after long hours of exposure to harmful noise. However, the most affected group are industrial and construction workers who are constantly exposed to high levels 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 showed teenagers tend to develop hearing loss at an early age due to prolonged music listening habits. As a parent, you can prevent hearing loss from occurring 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. The safe listening volume of a general device is always below 80% of the overall volume.

多大声算过于响亮？

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 these examples: a normal conversation between you and others is around 60 decibels, while noise from a motorcycle is around 95 decibels. Listening to music at maximum volume via headphones 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 that every increase of 3 decibels reduces half of the permissible time limit exposure of the noise.

记住，始终注意环境中的危险噪音。如果您察觉到噪音，请用手捂住耳朵或简单地远离它。您的听力需要关注！