Home Theater - Science of Sound -
Components
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Impact of Multiple Speakers , Distance, and
Placement
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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. |
Speaker placement within room:
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Amplifier power (watts):
(watts) |
Number of speakers:
(Note: Program assumes each speaker has the same sensitivity) |
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Listening position (number of feet from speakers):
feet |
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Important
Background Information
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- 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.
Perceptions of Increases in Decibel Level
Imperceptible Change - 1dB
Barely Perceptible Change - 3dB
Clearly Noticeable Change - 5dB
About Twice as Loud - 10dB
About Four Times as Loud - 20dB
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
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.
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Continuous dB
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Permissible Exposure Time
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85 db
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8 hours
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88 dB
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4 hours
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91 db
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2 hours
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94 db
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1 hour
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97 db
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30 minutes
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100 db
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15 minutes
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103 db
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7.5 minutes
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106 dB
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3.75 min (< 4min)
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109 dB
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1.875 min (< 2min)
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112 dB
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.9375 min (~1 min)
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115 dB
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.46875 min (~30 sec)
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