Decibels

[firko]

I think Jonseys Black Betty came in around 102 and it hasn't got a muffler at all!

[Rosco400]

I think Jonseys Black Betty came in around 102 and it hasn't got a muffler at all!

Does this mean there could be an inconsistancy with multiple readings, I was dumb founded when he said he was tested at this but Black Betty with no muffler i would have thought would be of the richter scale

[Tim754]

Got a mate to come around with a noise tester just before, so I fired up the 754 in the shed (no front end at present fitted) Now it has 4 headers going into a 4 into 1 collector .then no muffler, just a chrome 60mm droopy tail piece that directs pipe under sidecars floor thats all. Worst result "102" decibels at approx. 6000 rpm??this in shed??? Shit better rename the HBS "Whispering death"

[Doc]

http://www.mccofnsw.org.au/a/117.html

this article explains kind of explains why the lower db reading Tim. Bottom line is worth a read and for those who don't wish to read the whole thing here is that bottom line.

a motorcycle with a deep "clean" note will have the energy level discounted in the test, but a motorcycle with higher frequencies in the exhaust note may not only fail the test, be also be "annoying'. Here we have the reason why "trail bike noise" is marked for attention by authorities, yet ordinary street registered machines mostly pass unnoticed by the general population

not so much how loud it is but moreso it's the the energy level or frequency which is tested, what we actually hear with our ears is deceptive and not exactly what is measured. Clear as mud 

[Tim754]

Yep looks like a case of....if you can't dazzle them with brilliance, baffle them with bullshit...........

[pokey]

Annoyance?
 They still let people play bagpipes and ABBA records

 sheesh

[Doc]

yeah! an' I bet AC-DC play their bagpipes at more than 98dB 

[pokey]

I get it now. we need to stick a nice long stinger on the end with some "Tuning" holes  along its length and be able to play Its a long way to the shop if ya wanna sausage roll by covering holes with toe of your boot  

[Doc]

impressive stuff eh Pokey! I can just hear me in the pits.."oh yeah she's goin' great now thanks mate! I dropped an octave and gave her a little more reverb..it was distorting badly up top earlier"

[Gerard De Ruyter (Twistandshout)]

how do you tell if your muffler needs repacking - does it get louder (cause more of the noise goes straight thru cause packing full of carbon) or quieter?

[vandy010]

i had my RT1 on the meter on the weekend, it runs a stock shape RT1 pipe with the baffles removed from the chamber and a shortened well packed PE silencer. at 2500rpm it was running 92db but for a motor that size the revs are supposed to be 4500rpm and i feel it would have failed {the poor bike would probably only rev to about 5500 anyway}. we were in suburbia while testing and kept the revs down so as not to bring too much attention to ourselves. my bike i feel is one of the quieter ones, so go figure that!
also tested was a current model 250f husky enduro that ran an aftermarket pipe and it was easilly well under the 96db.

[Doc]

Twistandshout, she'll be louder because of the reason you stated. The carbon chokes the perforation holes and the packing thus reducing the amount of sound it can absorb. It's like liquid into this chalk..it bloody well should get in but it doesn't! 

Vandy, this is basically what I feared, the way the sound is measured is inconsistant with capacity and engine type. There is noise and then there is really annoying noise. This is what some of the new generation 4 bangers produce, annoying noise. On a meter it may not read much as dB but this sound travels much further for some reason. It's a very 'flat' droning sound that seems to cut in over everything else and I can fully understand the complaints are forthcoming. On a VMX day, there's not a whisper to be heard and the vintage track is on the closer open side of the complex. I still say it's a cop out rule and only done to protect the guilty I believe the sound should be measured from a minimum distance of 500 metres 

[Freakshow]

thats the post with the 'A" type meters they are set up to pick up high frequency, thus the 2 smokers get a bad run off the bat

[Gerard De Ruyter (Twistandshout)]

thanks doc.  means my muffler must still be good cause its one of the quietest mx bikes i've had. 

and i agree with your description of the sound of modern four bangers - 'drone' is right.  none of the excitement that full-on two smokers on the pipe generates.  but penetrating nonetheless.  double negative.

[gorby]

I put this modern style muffler on the race bike and it went 99db

It added a couple of kilos and needed stronger brackets and supports.

I'm sure that some mufflers and baffles "fell off or blew out" as soon as the noise meter was put away

will this be the future protest issue ?