I guess this question would be for someone who has been ticketed or pulled over for loud exhaust. Where or how do they measure the dba's? Do they put the meter right behind the exhaust or next to it? Is there a standard how they measure it?

I would like to measure mine and would like to measure it correctly. Thanks for the info!

 

i think they are referred to as db's. i got mine recorded by some harley dudes at the daytona speedway last year. i think they put a wand of somesort directly into the pipe.

 

i think its 3ft away at a 45degree angle from the exit point of the exhuast

 

I dont think theres one bike In new jersey that would pass that test...but its funny seems like them race bikes are making more noise these days..............I was next to a guy the other day I could not even hear my bike over this screeming thing and the guy was just crusing

 

They use different positions and distances for how they measure. It seems like there is not just one standard way to do it.

 

The actual test method used will vary from state to state. Some may stick a sensor up the pipe, some may take the reading from 20-30 feet away, some directly from behind, some off at a 45 degree angle. Each of the above will have a different limit based upon how the test is set up. Naturally for a test that sticks the sensor up the pipe the pass/fail limit will be lower than the test taken from 25 feet.

The test will be made almost all the time using dBA as the measurement unit, it is a fairly recognized measurement unit used primarily in the audio recording industry. For reference, 0 dBA is about the softest sound that can be heard by the human ear. 3 dBA is twice as loud as that, 6 dBA is 8 times that and so on. Most state limits are in the upper 80s to low 90s as their pass/fail spec.

 

dba is correct -
Stands for decibel (db) on the “a” weighted scale (closer to the response of the human ear) You really need to check local laws.

 

Actually, unless you are in an anechoic chamber, you will never experience 0 db. The noise level in a very good recording studio is still around 40 db, and your average sound level in your house will be around 65-70 db. Also, when sound level increases by 6 db, it sounds twice as loud, not 8 times louder. Sound level is logorithmic, not linear.

 

You can bet it will be standardized or it should be.Even if it is you can be assured it will be up to the LEO who stops you.

 

Soundman, looks like from your name you're in the industry so certainly not gonna argue about sound measurements. I'm in the optics industry where we use the dB scale to measure optical power levels so I went back and checked my math and actually we're both wrong to a degree. A 3 dB change in power level is 2 times (1.99), a 6 dB change is 4 times (3.98) and a 9 dB change is 8 times (7.94).
This is probably way too far down in the weeds for a lot of people but a little bit of a pet peeve and also so folks understand the terms when they see them. The term dB is a relative measurement between two levels. So to say my pipes are 80 dB loud means nothing because I don't know what sound level you referenced your measurement against. Now if you say your pipes are at 80 dBA that says your pipes are 80 dB louder than a reference sound level. Differnet industries use different reference levels. In optics we use 0 dBm in reference to 1 milliwatt, I looked up the one for sound and got real confused but appears to be 20 microPa (don't have mu symbol here). If you're still with me this far you're probably a pretty sick pup but I digress. BTW, I got my statement about the 0 dBA sound level from Wikipedia.

"The decibel is commonly used in acoustics to quantify sound levels relative to some 0 dB reference. The reference level is typically set at the threshold of perception of an average human and there are common comparisons used to illustrate different levels of sound pressure. As with other decibel figures, normally the ratio expressed is a power ratio (rather than a pressure ratio).

For everyone's enjoyment, sound levels for some various interesting objects:

Source of sound Sound pressure Sound pressure level Sound in air pascal RMS dB re 20 μPa
western Pacific Ocean 1979 (Typhoon Tip) & Agata, U.S.S.R. 1968 87,000 - 108,400 Pa 192.8–194.7 dB calculated
Krakatoa explosion at 100 miles (160 km) in air -- from estimate of energy of explosion[dubious – discuss] 20,000 Pa 180 dB
Stun grenades 6,000–20,000 Pa 170–180 dB rocket launch equipment acoustic tests ~4000 Pa ~165 dB
M1 Garand rifle being fired at 1 m 5,023 Pa 168 dB
Jet engine at 30 m 632 Pa 150 dB
Threshold of pain 63.2 Pa 130 dB
Vuvuzela at 1 m 20 Pa 120 dB(A)[6] Hearing damage (possible) 20 Pa approx. 120 dB
Jet engine at 100 m 6.32 – 200 Pa 110 – 140 dB
Jack hammer at 1 m 2 Pa approx. 100 dB
Traffic on a busy roadway at 10 m 2×10−1 – 6.32×10−1 Pa 80 – 90 dB Hearing damage (over long-term exposure, need not be continuous) 0.356 Pa 85 dB
Passenger car at 10 m 2×10−2 – 2×10−1 Pa 60 – 80 dB TV (set at home level) at 1 m 2×10−2 Pa approx. 60 dB Normal conversation at 1 m 2×10−3 – 2×10−2 Pa 40 – 60 dB
Very calm room 2×10−4 – 6.32×10−4 Pa 20 – 30 dB Light leaf rustling, calm breathing 6.32×10−5 Pa 10 dB Auditory threshold at 1 kHz 2×10−5 Pa 0 dB