How noise damages hearing
Sound is detected by delicate hair cells inside the cochlea. Loud noise physically flattens them, and unlike skin or bone they do not regenerate. Damage tends to appear first as a notch around 4000 Hz on the audiogram, long before the patient notices anything in conversation.
The first warning sign is usually temporary: muffled hearing or ringing after a loud shift or a loud event. It recovers overnight in the early years. Once it stops recovering, the loss is permanent.
How much is too much
The accepted occupational limit is 85 decibels averaged over eight hours. Every three decibels above that halves the safe exposure time: eight hours at 85 dB, four hours at 88 dB, two hours at 91 dB, and so on.
For a practical rule, if you must raise your voice to be understood by someone an arm's length away, the environment is loud enough to need protection.
- Busy street traffic: around 80 dB
- Workshop machinery and generators: 90 to 100 dB
- Port and construction equipment: 95 to 110 dB
- Amplified music at a club or concert: 100 to 115 dB
Protection that people actually wear
Foam plugs from a pharmacy work only when inserted correctly, and most are not. Custom-moulded plugs made from an impression of your own ear seal reliably, sit comfortably for a full shift and are far more likely to stay in.
Musicians and sound engineers should use filtered plugs, which reduce level evenly across frequencies so the music still sounds like music rather than a muffled version of it.
Screening for noise-exposed workers
If you work in noise, have a baseline audiogram taken and repeat it annually. Comparing year to year catches a shift while it is small and while changing protection can still preserve what remains. We provide signed audiograms for occupational and maritime medical requirements.