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Old 15th September 2011, 12:42 PM   #1
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Default Twice the sound level is +6dBA right?

I have seen some conflicting info and I would just like to confirm that +6dBA is twice the sound level (noise). It makes sense to me because Sound level is the square of the sound amplitude but I have seen many a place saying that this thought is wrong.

thanks
 
Old 15th September 2011, 12:52 PM   #2
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if the voltage goes up by 2x that's +6db
if the voltage goes down by 1/2 that's -6db
if the power goes up by 2x that's +3db
if the power goes down by 1/2 that's -3db

your ears are logarithmic you need 10x (10db power) to hear 2x as loud volume (depends on frequency) see fletcher/munsen curves wiki

you need 1/10 th power to get to 1/2 as loud
 
Old 16th September 2011, 01:44 PM   #3
DF96 is offline DF96  England
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You maybe confusing ratio with level. +6dB is a ratio, which is four times the power; other things being equal this also means twice the voltage or twice the sound pressure. +6dbA is a sound level, which is 6dB above the reference level (often 0.02mPa pressure?) and measured using an 'A weighting filter'. A bare dB figure is always expressing a ratio between two numbers. In some cases there may be a standard reference level but this should normally be indicated with a suffix e.g. dBm means dB with respect to 1mW. Unfortunately, sound people often say 6dB when they mean 6dBA.

As multisync says, 6dBA won't sound twice as loud as 0dBA.
 
Old 16th September 2011, 02:34 PM   #4
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No 3 db is twice the sound pressure level. It is measured in power. Voltage times current is power so if you have a fixed resistance and double either voltage or current you also automatically double the other so you get four times the power or 6 db more.

The rule of thumb (which is inaccurate) is that 3 db is just a perceptible change and a 10 db increase sounds twice as loud.
 
Old 16th September 2011, 03:50 PM   #5
DF96 is offline DF96  England
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According to the Australians sound pressure works like voltage, not power. 6dB is twice the sound pressure.
 
Old 16th September 2011, 03:59 PM   #6
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Quote:
Originally Posted by DF96 View Post
According to the Australians sound pressure works like voltage, not power. 6dB is twice the sound pressure.
That's nice. Why don't you take a sound level meter and measure any source. Then go to twice the measurement distance and take another reading. Let me know how much the level decreases as you double distance.
 
Old 16th September 2011, 04:18 PM   #7
sreten is offline sreten  United Kingdom
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Hi,

+6dBA is 4 times the power according to A weighting. 1B or 10dB is x10.

SPL, like voltage levels in equipment, is rated according to the power.

So +3dB in real voltage level (2x) is actually +6dB(4x) in signal level.
+10dB in real voltage level (10x) is actually +20dB(100x) in signal level.
Same goes for SPL, up pressure by x1.4 and SPL doubles i.e. +3dB.

+3dBA is twice the power A weighted.

Quote:
dB: What is a decibel? : Australians
Its not wrong, that what is says, if you can read.

+6dB SPL is twice the pressure, but not twice the SPL, its 4 times the SPL.

rgds, sreten.
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Last edited by sreten; 16th September 2011 at 04:26 PM.
 
Old 16th September 2011, 04:43 PM   #8
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But is it twice as loud?
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Old 16th September 2011, 04:48 PM   #9
sreten is offline sreten  United Kingdom
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Quote:
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But is it twice as loud?
Hi, Of course not, that is accepted as ~ 10dB or 1 Bel, rgds, sreten.
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Old 16th September 2011, 04:51 PM   #10
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Right. Thus the confusion. 3dB, 6dB, 10dB. Which is "twice as much"?
 

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