source: freeimages.com |
Healthy human ear can usually register sounds for intensity of 0 dB - this is the threshold point. Some extremely sensitive individuals can hear sounds even weaker and theoretically should have gone in the measurement of auditory sensitivity to minus values. Simply, the human ear is extremely sensitive organ and is not designed for prolonged toleration of loud noise.
It's good to remember :
Danger to human hearing begins at around 85 dB. Normal human ear can withstand continuous noise of this intensity without damage for about 8 hours a day. Every 3 dB more, shortens time by half. So e. g. 91 dB is a safe value for only two hours a day, then we should take a rest for the day. Of course it also depends on the sensitivity of a particular individual, someone can endure more, someone less. Noise with an intensity of 130 dB and higher causes hearing damage almost immediately.
This image will help you get a rough idea about various noise sources:
source: eardefendersforkids.co.uk |