Useful Table - Those Decibels Again

Common Noise Levels and Typical Reactions Below is a useful comparative table of noise levels. But what does Apparent Loudness mean? Alright, it is a bit complicated! Let us start at a noise level of 70 db. We experience this sound because a certain level of noise energy is reaching our ears. Now suppose we double the energy reaching our ears. A noise meter will tell us that the noise level is now 73 db (a rise of 3 db in noise measured on the meter is always due to a doubling of the noise energy level in the air around us, e.g. 43 db has twice the noise energy of 40 db, 63 db has double the noise energy of 6o db and so on) . But the sense of sound in our brain does not react to the noise energy level in the same ratio. A rise from 70 db to 73 db does not feel to us like a doubling of the noise, it sounds like much less. For us to think that the noise has doubled, the noise energy level outside has to increase TEN times (which a noise meter will register as an increase of 10 db)! So if we start at 40 db and increase the noise to 50 db, the real noise energy outside has increased 10 times, but our ears tell us that it has only increased 2 times i.e. the apparent loudness has doubled. If we increase further to 60 db, the real noise is now 100 times greater but our ears tell us that it has increased 2 times from 40 to 50 db, and another two times from 50 to 60 db or 2 x 2, or 4 times altogether. Increase the noise once more from 60 to 70 db (the noise outside has now gone up 1000 times more than at 40 db); our ears tell us it has gone up 2 x 2 x 2 or 8 times compared to 40 db. Finally increase the noise outside another 10 times. A meter will record an increase from 70 to 80 db; the actual noise energy has now increased 10,000 times but our ears tell us it has gone up 2 x 2 x 2 x 2 or 16 times greater than it was at 40 db. So there you are! Let me summarise: 40 db Reference level -----------Real Noise Level ----------APPARENT LOUDNESS 50 db -----increased by 10-------------- increased by 2 60 db -----increased by 100------------ increased by 4 70 db -----increased by 1000 -----------increased by 8 80 db -----increased by 10000 ---------increased by 16 ************(compared to the levels at 40 db)**********

Activity	Noise Level [dB(A)]	Apparent Loudness	Typical Physical Response
Rocket launching	180		Danger level
Threshold of pain Gunshot Jet engine taking off	140		Danger level
Military jet Air raid siren Shotgun Hydraulic press (3 m away)	130	512 times as loud	Limited ability to hear amplified speech. Noise may cause pain. Can damage hearing after 3.75 minutes exposure per day
Car horn Propeller aircraft Air-raid siren	120	256 times as loud	Can damage hearing after 7.5 minutes exposure per day
Sand-blasting Squealing pigs Inboard motorboat Typical night club Unsilenced motorcycle (7m away)	110	Over 128 times as loud!!	Maximum vocal effort. Can damage hearing after 30 minutes exposure per day
Amplified Rock Music	110-130	Over 128 to 512 times as loud!!	Can damage hearing after 3.75 - 30 minutes exposure per day
Helicopter Motorised/power mower	105		Can damage hearing after 1 hour exposure per day
Jet takeoff @ 500m Train horn @ 30m Diesel truck Pneumatic drill/jackhammer	100	64 times as loud	Can damage hearing after 2 hours exposure per day
Heavy truck @ 15m Busy city street passing motorcycle Lawn mower Loud shout Sreaming child	90	32 times as loud	Very annoying. Can damage hearing after 8 hours exposure per day
Average factory Electric shaver	85
Busy traffic intersection Motorway construction site Outboard motor Alarm clock (with bell) Freight train (15m away)	80	16 times as loud	Annoying .
Motorway traffic @ 15m Roadside traffic Train horn @ 500m Vacuum cleaner Mixer electric sewing machine Noisy restaurant Conversation in a loud voice	70	8 times as loud	Telephone use difficult.
Washing machine/dishwasher	65
Light car traffic @ 15m City or commercial areas Noisy office Normal conversation Clothes dryer Background music	60	4 times as loud	Intrusive.
Quiet office	50	2 times as loud	Speech interference.
Refrigerator	45
Quiet residential area Kitchen/bathroom Public library	40	Arbitrary Base Reference Level	Quiet .
Leaves rustling Very soft music Recording studio Living/dining/bedroom	30	1/2 as loud	Very quiet.
Threshold of sound perception	10	1/8 as loud	Just audible.
Threshold of hearing	0	N/A	Not audible.