I finally brought my Sound Level Meter home to do some testing.
Test Standard: SAE J1287

Method:
-Meter @ outlet elevation.
-At 45 dgree angle from bike centerline and 20" away.
-On black top, no reflective surfaces near.
-Engine in neutral @ 1/2 the 10,500 RPM Redline (5,250 RPM).

Conditions:
-Wind of 0-2mph.
-70 F and 87% Humidity.
-Ambient background level of 42dBA.

Equipment:
-Quest 2800, Type 2 with current calibration and currently calibrated calibrator.
Settings:
-dBA, slow response

Results:
-Totally stock 2007 KLX 250s 84dBA
-HMF with QC insert. 96dBA
-HMF without QC insert. 98dBA

Note:
1) An 8-10dB increase is percieved by the ear as being twice as loud.
2) These exhausts typically attenuate the higher frequency content and the remaining lower frequency content has a higher energy level and travels a greater distance.
3) The stock pipe indicates 80dBA max, but that is probably a test in an anechoic chamber.

If anyone in the Syracuse area has other manufacturers slip on or full systems and want to stop over, we can get readings for them to compare.

 

The meter I use is if the wax in my ears vibrates out then its loud enough.

 

If your stock reading is slightly high from what the factory says it is, then the HMF reading is in line as being slightly high too.

We need to get a reading of the FMF Q4 as they claim most are under 93dB I think.

 

Swear mine got louder with the snorkle out...

Id luve to see the same bike specs with lid off etc....Then a slip on....Then the 300 header..


Sound clip would be friggin awesome....Im a small hike away from your place but wouldnt mind making it on the 2Do before seasons ends typea run....PM me if interested...14609

Rocco

 

Maybe I missed it, did you test at a specific RPM? If so, what?

 

7200rpms is the ripper.....I get the deer to run for the hills at 72..

 

I knew I'd forget something! The standard is to test at 1/2 the rated rpm 10,500, so all readings were taken @ 5,250 rpm. I'm sure that it may be louder at a higher rpm, but this rpm must may be considered a crusing RPM?
A test without the cover would most likely be higher, since the intake noise would not be reduced.

 

Bingo

If the normal study is 6th gear at 5200rpms....That would be slick....Thats gotta be about an 1/8 throttle on the dyno....Thats how I have to pass the police in town sorta throttle noise combo.....4th or 5th throttle at 7300rpmz would be interesting to see with your same KLX..........

Cool thread........

Rocco

 

The test number that I have for the stock bike dBA, may also be higher because of variables such as radiated noise from sources such as the timing chain -it may possible that factory tests block the noise that is radiated from these other sources and is the "true" level of only the exhaust -but not "true" in the sense of the real world.

 

I wear earplugs. Two Brothers pipe and no airbox lid. Sounds fine to me.