- 1decibel (dB) is roughly the smallest change we can perceive.
- Doubling the amplifier wattage results in ONLY a 3dB increase in volume ("slightly louder"). Switching from a 50 watt amplifier to a 100 watt amplifier or from a 100 watt amplifier to a 200 watt will only increase the volume by 3 dB as long as you use the same speakers.
- In order to double the current volume of the home theater requires roughly a 6 to 10 dB increase. A 6 dB increase requires 4 times the power! and a 10 dB increase requires a 10-fold increase in amplifier power.
Perceptions of Increases in Decibel Level
Decibel: The decibel (abbreviated dB) is the unit used to measure the intensity of a sound.
1) On the decibel scale, the smallest audible sound (near total silence) is ~0-1 dB.
2) A sound 10 times more powerful is 10 dB.
3) A sound 100 times more powerful than near total silence is 20 dB.
4) A sound 1,000 times more powerful than near total silence is 30 dB.
* Near total silence - 0 dB
* A whisper - 15 dB
* Normal conversation - 60 dB
* A lawnmower - 90 dB
* A car horn - 110 dB
* A rock concert or a jet engine - 120 dB
* A gunshot or firecracker - 140 dB
Imperceptible Change - 1dB
Barely Perceptible Change - 3dB
Clearly Noticeable Change - 5dB
About Twice as Loud - 10dB
About Four Times as Loud - 20dB
[Any sound above 85 dB can cause hearing loss, and the loss is related both to the power of the sound as well as the length of exposure.]
dB SPL laws
Impact of the various changes on sound levels
Double amplifier wattage - increase of +3 dB
Double number of speakers - increase of +3 dB
Double distance from sound source - Decrease of - 6 dB
Halve distance from sound source - Increase of +6 dB
Double driver excursion - increase of +6 dB (note: Equivalent to doubling wattage and # of speakers)
-----Placement of Speakers--------------
Place speaker on the floor - increase of +3 dB - half loading
Place speaker on floor, and against a wall - increase of +6 dB - quarter loading
Place speaker on floor, near a wall, and in the corner - increase of +9 dB eighth loading