Here's an interesting piece of noise trivia from the sensible and well organized lap of Mother Nature.
According to the American Tinnitus Association (ATA) a person's hearing will be damaged when exposed to sounds of over 85 decibels (dB) for more than eight hours. The noise of a screaming child is about 110 dB. The recommended maximum exposure at this level is about half an hour. This might help explain why parents so quickly attend to their children.
In fact a screaming child's dBs are higher than a chainsaw and only slightly less than a rock concert, thunderclap or a jet plane.
The human hear suffers damage after about 108 seconds of 130dB. At 140dB the ear experiences excruciating pain.
Here is how the intensity of some sounds are ranked:
- Whisper - 30dB
- Refrigerator - 40dB
- Rain; normal conversation - 50dB
- Daytime suburban street - 55dB
- Sewing machine - 60dB
- Washing machine - 70dB
- Alarm clock (2 feet or about .6 metres away) - 80dB
- Average traffic; electric razor - 85dB
- Hair dryer; subway train - 100dB
- Lawn mower; chainsaw - 105dB
- Screaming child; stereo headset - 110dB
Rock concert; thunderclap - 120dB
Jet plane (100 feet or about 30 metres away); jackhammer - 130dB
Rocket launch - 180dB
A dB is not a linear measurement like a ruler. Instead it is a logarithmic measurement. In other words 20dB is ten times more powerful than 10dB; 30dB is ten times more powerful than 20db and so on and so forth. This means for instance that a screaming child (110dB) is 100,000 times more powerful than your average sewing machine (60dB) since the dB difference is 50 or 10x10x10x10x10. Ah the sound of domestic bliss.
The dB measurement owes its name to engineers from the Bell Telephone Laboratories who developed the term in honour of their founder the inventor Alexander Graham Bell. (The deci means one tenth.)
For more information see:
www.phys.unsw.edu.au/jw/dB.html
www.dallashodgson.info/articles/Acrobat/DecibelPrimer.pdf