Twice the sound level is +6dBA right?
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 15th September 2011, 12:42 PM #1 diyAudio Member   Join Date: Sep 2010 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
 15th September 2011, 12:52 PM #2 diyAudio Member   Join Date: Jan 2008 Location: Carp 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
 16th September 2011, 01:44 PM #3 diyAudio Member   Join Date: May 2007 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.
 16th September 2011, 02:34 PM #4 diyAudio Member   Join Date: Nov 2008 Location: Oakmont PA 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.
 16th September 2011, 03:50 PM #5 diyAudio Member   Join Date: May 2007 According to the Australians sound pressure works like voltage, not power. 6dB is twice the sound pressure.
diyAudio Member

Join Date: Nov 2008
Location: Oakmont PA
Quote:
 Originally Posted by DF96 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.

diyAudio Member

Join Date: Nov 2003
Location: Brighton UK
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.

 16th September 2011, 04:43 PM #8 diyAudio Moderator     Join Date: Oct 2004 Location: North Carolina Blog Entries: 4 But is it twice as loud? __________________ Take the Speaker Voltage Test!
diyAudio Member

Join Date: Nov 2003
Location: Brighton UK
Quote:
 Originally Posted by Pano But is it twice as loud?
Hi, Of course not, that is accepted as ~ 10dB or 1 Bel, rgds, sreten.
__________________
There is nothing so practical as a really good theory - Ludwig Boltzmann
When your only tool is a hammer, every problem looks like a nail - Abraham Maslow

 16th September 2011, 04:51 PM #10 diyAudio Moderator     Join Date: Oct 2004 Location: North Carolina Blog Entries: 4 Right. Thus the confusion. 3dB, 6dB, 10dB. Which is "twice as much"?

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