The decibel (dB) is the unit used to measure the intensity of a sound. The logarithmic decibel scale measures sound base on human hearing.
Many regulatory noise limits are specified in terms of A-weighted decibels, or dBA, which is adjusted so that low and very high frequencies of sound are given less weight - as perceived by human ears. Zero decibels (0 dB) is the quietest sound audible to a healthy human hear.
From there, every 3 dB increase represents twice the sound intensity, or acoustic power.
Loudness and intensity are different. Whereas a 10dB increase equtes to 10x in intensity, is is perceived to be only twice as loud.
If one vacuum cleaner is measured to be 70dB, then ten vacuum cleaners has an acoustic power of 80db (not 700dB!), and they would sound only twice as loud as one vacuum cleaner.
You would need 100 vacuum cleaners to reach a noise level of 90dB, and together they would sound only four times as loud as a single vacuum cleaner.
Air conditioners range from 40-60 dB. With an advance in technology, newer models of air conditioners lean towards the lower end of the spectrum and are often described as ‘whisper quiet’.
Normal human conversation is 60 dB and is the best benchmark for comparison. If something is advertised to be below 60 dB, you’ll know it is quieter than you speaking. Conversely, anything above 60 dB may drown out your voice.
The loudest recorded snore is a window-rattling 111.6 dB, by Briton granny Jenny Chapman!
Police sirens are loud to warn motorists of their presence. It has to be louder than human conversation so that it won’t be ignored. This is also why a lot of motorbike traffic officers wear ear plugs.
A motorcycle passing you, the subway and a garbage truck are some of the everyday occurrences at 100 dB. Extended exposure to sound at this level can lead to hearing damage. The recommended maximum noise exposure limit is 85 dB for not more than 8 hours.
The loudest tennis grunt is made by Michelle Larcher de Brito at 109 dB!
Always put on hearing protection when working in noisy industrial settings. Full earmuff style protection is recommended over ear plugs. Other examples of sound at this range are oxygen torches, jackhammers and pneumatic riveters.
Sound at this level is over the pain threshold for most people. Do NOT be near sound at this level for more than a few seconds. Immediate damage to your hearing is possible.
The Tunguska Meteor explosion in 1908 was measured to be 300-315 dB – similar to the impact of 1000-Mega-ton bombs!
What do you do when you hear a gun shot? You run. Similarly, when you hear something as loud, get far away as it could lead to a loss of hearing.
A space shuttle take-off or a volcano explosion can go as loud as 180 dB. Your eardrum can rupture at this level. The good news is: you’ll probably never be standing next to a rocket launch or a volcanic eruption.
The loudest sound possible is 194 dB. At this level, sound waves become shock waves and is enough to kill a human. Sonic boom!
National Institute for Occupational Safety and Health (NIOSH)
Center for Hearing and Communication, Common environmental noise levels
Purdue Science, Department of Chemistry, Noise Sources and Their Effects
HealthLinkBC, Harmful Noise Levels
IAC Library|Comparitive Examples of Noise Levels
California Department of Transportation, Loudness Comparison Chart