I've been considering the muffler from PSI but wanted to know if anyone here had tried it..
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either I don't understand noise levels or their advertising is confusing:
Their DC models range from 62 to around 80 DB or so...
They say that the muffler will reduce the noise 5 to 10 db resulting in "up to"
50% noise reduction..
I counted on my fingers and toes and realized that 10 db is not half of even 60 db... maybe db is exponential or something? (vague recollection of that)
On a graph the increase in noise from 5 to 10 to 20 db does not show up as a straight line. Think of income taxes, the more you make the higher percentage of your earnings is taxed. Decibel ratings are similar.
A 6db reduction is a 50% reduction. So 12 db would be 50% plus 50% of the remainder or 75%. You can estimate from this. If you need a more precise answer, you need to start using formulas.
"Chris Richmond - MD6-FDC ~" wrote in message news:ealbrh$6tl$ snipped-for-privacy@news01.intel.com...
decibel One entry found for decibel.
Main Entry: deci·bel Pronunciation: 'de-s&-"bel, -b&l Function: noun Etymology: International Scientific Vocabulary deci- + bel 1 a : a unit for expressing the ratio of two amounts of electric or acoustic signal power equal to 10 times the common logarithm of this ratio b : a unit for expressing the ratio of the magnitudes of two electric voltages or currents or analogous acoustic quantities equal to 20 times the common logarithm of the voltage or current ratio 2 : a unit for expressing the relative intensity of sounds on a scale from zero for the average least perceptible sound to about 130 for the average pain level 3 : degree of loudness; also : extremely loud sound -- usually used in plural
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nope, Logarithmic (base 10, not neeperian logs)...
Db mesure the difference (actually, the Ratio) between 2 sounds using the following formula: Db = 10 LOG(Sound A / Sound B) (or, more precisely Signal A / Signal B)
so, if Signal B is 1/2 of signal A (50% reduction), Db = 10 Log(1/2) ~= -3 (ie: reduction of 3 Db = 1/2 of the signal)
10Db reduction, ie: -10 = 10 LOG(A/B) means that A/B = 10^(-1) = 0.1 ie, the sound power has been reduced by a factor 10!
when a sound level is given in DB, it is assume that it is a mesurement of that sound level comared with a 'unit' sound level which has been pre-defined (but I do not remember it's definition).
now, another problem is that the human hear does not perceive different sound frequency in the same way, so a system which reduce the sound power by
10db in a certain frequency range might make no difference to your hears (for example, if it does -10 db at 20Khz (ultra sounds) it will do nothing to help you)... what is important to see is the 'frequency response' of the muffler, ie: the curve that shows the Db reduction for the whole audible frequency spectrum (usually from 20hz to 20Khz)... and ensure that the response is as high as possible in the 60 to 4000 Hz range (your main hearing band).
For some reason, as soon as you start talking about sound, audio etc any truth in advertising seems to fly out the window. They use a lot of tricks to get to the number they advertise. There are a number of ways to measure dB. Some relate to what you hear, some don't It is like those monster speaker wires. If it sounds better to you it works.
There are already plenty of replies that address the physics... I'll let you go through them and not repeat them. On the matter of your first question, yes, I have that exact one. I've never run the dust collector without it so I can't really say how much difference it makes. What I can tell you is that you can easily carry on a conversation with the dust collector running without raising your voice. You sure can't say the same about my shop vac. I'm highly satisfied with both the Penn State dust collector and the muffler.
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