Home Theater - Science of Sound -  Components

home theatre

Speaker Sensitivity, Specified output - Determine Amplifier Power

Enter your Speaker Sensitivity (SPL)   (dB 1W/1M)
1 watt/1meter SPL (sound pressure level) - Usually printed on the back of your speaker cabinet.
Highly sensitive speakers (sensitivity >95 SPL or even > 100), can produce extreme sound levels with minimal power. 
Desired output in decibels (dB) you would like to achieve (dB)
Dave reproducing concert sound for a few minutes....

Important Background Information

  • 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 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.

Sound Levels

barely audible 0 dB - Threshold of hearing
10 dB - Rustling leaf
20 dB - very quiet  - Quiet room
30 dB - Soft whisper
40 dB Quiet library
50 dB Average home
60 dB - moderately loud. Ordinary conversation, Light traffic.
70 dB - Vacuum cleaner, Heavy traffic
80 dB - Very loud.  Garbage disposal.
90 dB - Diesel truck
100 dB -  Snowmobile, Motorcycle, Train, garbage truck, 15th row of rock concert, chainsaw,
          Level - 5 to 10 using earbuds and a standard IPOD or walkman.  Uncomfortably loud. 
110 dB - Jackhammer, power saw, symphony orchestra, front row of rock concert, Car horn.  Extremely loud
120 dB - Rock concert, Jet engine.  Painful.  Threshold of pain.

Permanent Hearing Loss

Decibel Exposure Time Guidelines Accepted standards for recommended permissible exposure time for continuous time weighted average noise, according to NIOSH and CDC, 2002. Each 3 decibel (dB) increase above 85 decibels cuts the permissible exposure time in half.   Exceeding these times will likely result in permanent hearing loss.   
Continuous dB Permissible Exposure Time
85 db 8 hours
88 dB 4 hours
91 db 2 hours
94 db 1 hour
97 db 30 minutes
100 db 15 minutes
103 db 7.5 minutes
106 dB 3.75 min (< 4min)
109 dB 1.875 min (< 2min)
112 dB .9375 min (~1 min)
115 dB .46875 min (~30 sec)