Decibel readings from various exhausts

[Monochrome]

http://buschurforums.com/forum/showp...2&postcount=35

[David Buschur]

Interesting monchrome. I can't believe there isn't a huge difference in the sound. It's even harder to believe the lack of loss of power, generally I see the cats kill power. What cat did you put on the car?

[Monochrome]

Interesting monchrome. I can't believe there isn't a huge difference in the sound. It's even harder to believe the lack of loss of power, generally I see the cats kill power. What cat did you put on the car?

I was surprised too! It's your 3" catco cat that you sell for your exhausts. ...and yes I did check. The filter material is still in there.

Maybe it's just not a large enough restriction at this power level. Think I'll hold onto it for testing purposes when I get a larger turbo in the future.

[JorgeYaHeard]

Hi there Dave,

I thought I might clarify the human ears perceived response to loudness and the db scale. Loudness is measure of Phons and is very similar to the db scale at moderate listening levels. The db scale is a logarithmic scale, which means that you cant add/subtract as you normally would.

For every 10db increase there is a perceived doubling in loudness. This is the reason why sitting in a quiet room had @ 55db, but the exhausts @98db sounded well more than twice the volume.

"A" weighting the sound level meter, allows the meter to have a response similar to human hearing. "A" weighting basically reduces the sensitivity to high and low freq sounds, the same as the human ear does. Measuring using "C" weighting will give a db level higher than "A" as the freq response is flat.
If you are ever getting measured, please check that the meter is "A" weighted and on slow response.

There is normally an internal calibration signal button on the meter. This is used to adjust the needle on analog meters or zreo in didgtal meters.
Radio Shack sells quite a good analog meter, if anyone wants to buy one.

So please keep in mind this scale when viewing test results, as a 3db increase is a hell of alot in reality.

Thanks for making this forum a nice home for evo owners

Cheers
Aaron

I know this is really old, but I just wanted to correct this. Sound energy doubles every 3dB, not every 10dB. So, if you go from from 96dB to 99dB the loudness is doubled. Therefor if you go from 96dB to 106dB it is 3.33 times louder, huge difference. So for every 3dB you increase or decrease the sound, the perceived loudness is either doubled or cut in half.