The decibel scale is a logarithmic scale. Logarithmic scales are more useful than linear scales when data values are spread over a very large range. As a general rule, prolonged exposure to sound levels above 85 dB will cause slight hearing loss, and above 90 dB will result in mild to moderate loss. Above 100 dB, even short exposure can cause a permanent loss of hearing. Plastic earplugs can protect ear up to 20 dB. Some TVs emit a noise of 15,750Hz which is the frequency of the horizontal sweep oscillator.
Adults don t usually hear it, but children do.
We measure hearing loss by threshhold level where you can just barely hear a tone. The ear has an acoustic reflex that protects the inner ear from loud sounds in the same way that the pupil of the eye protects the eye by contracting in the presence of bright lights. However, the reflex requires a few hundredths of a second to respond, and so it cannot be relied upon to protect the ear in the event of a short sound such as an explosion.