Decibel Thread
Road Captain
Joined: Mar 2007
Posts: 660
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From: Southern Illinois
My meager understanding of decibels is that it is a measure of loudness. I wonder if there is a quantitative measurement of the quality or pitch of the sound of a muffler. Everyone always wants to know which muffler has the deepest sound. Does anyone know if there is an instrument to measure this. Sort of like a bass vs. treble on a stereo.
Grand HDF Member
Joined: Jan 2010
Posts: 3,514
Likes: 1,992
From: Vancouver BC
What are your thoughts on a radio shack meter vs a cell phone app? I read about the tests CDC did and picked one of the few apps they liked - its called SPLnFFT. The RS meter has two weighting choices, A of C - on the cell phone it has several weighting choices - dB, dB(A), dB(B) and dB(C) I have no idea which one to use and got no answers from the app designer. Any idea?
Personally I wouldn't trust the cellphone measurements regardless of app, only because their mics and audio processing circuitry are tailored to pass a narrow portion of voice grade audio within the greater audio spectrum. All the frequencies below 500 Hz and above 4 kHz are severely rolled off. For voice transmission and intelligibility those frequencies are useless and require more cellphone bandwidth, for those reasons the phone companies and manufacturers chop off that portion of the audio spectrum.
As far as meters go I haven't tested the Radio Shack one but I have tested similar $99 SPL meters, and for the most part they're pretty accurate. I found them to be within 1-1.5 dB of our calibrated meter. Hope that answers your question.
Last edited by Ride my Seesaw; May 9, 2015 at 04:56 PM.
Grand HDF Member
Joined: Jan 2010
Posts: 3,514
Likes: 1,992
From: Vancouver BC
My meager understanding of decibels is that it is a measure of loudness. I wonder if there is a quantitative measurement of the quality or pitch of the sound of a muffler. Everyone always wants to know which muffler has the deepest sound. Does anyone know if there is an instrument to measure this. Sort of like a bass vs. treble on a stereo.
A Decibel, or dB for short is just a ratio in which to measure power. Every 3 dB increase is a doubling of power. For example a 1 watt amplifier might be measured at 10 dB, a two watt amplifier would then measure a level of 13 dB (when using the same speaker.) The human ear however does not perceive this as a doubling of audio power. It will seem a little louder, just not twice as loud. For the ear and brain to 'perceive' it to be twice as loud you must increase the power 4 times, i.e. a 1 watt amplifier must be increased to 4 watts to 'sound' twice as loud to our ears. This would be a 6 dB increase in level.
Just an afterthought, those $20 digital electronic guitar tuners might work if you want to measure lowest frequency or 'rumble.' That, and a cheap SPL meter could give you a meaningful frequency and level measurement by which to compare exhaust systems.
Last edited by Ride my Seesaw; May 9, 2015 at 05:25 PM.
Knowing there are differences....
I think it's a great idea.
Non-scientific, if everyone uses the same app, and tells what device they are using, sitting on the bike, phone at chest level, we could still get a rough estimate.
And as my mo****r implies, I was a safety man for years, and had to take sound level readings with a high dollar unit weekly. I do understand the difference.
But I still like the idea as a rough-good-ol-boys method of comparison.
I think it's a great idea.
Non-scientific, if everyone uses the same app, and tells what device they are using, sitting on the bike, phone at chest level, we could still get a rough estimate.
And as my mo****r implies, I was a safety man for years, and had to take sound level readings with a high dollar unit weekly. I do understand the difference.
But I still like the idea as a rough-good-ol-boys method of comparison.
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