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Sorry if I'm beating a dead horse here, but I'm trying to decide about slip-ons for my '02 M620, and their perceived loudness could be a factor in the Peoples' Republic of Ann Arbor, where I live.

So, if stock cans measure at 80db, one hypothetical set of cans at 90db, and a second hypothetical set at 100db, is it _roughly right_ (you know, all else being equal and all that), that the 90db's are 10 times as loud as the 80db's and the 100db's are 100 times as loud?

(Whew, this motorcycling is _hard_!)
 

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technically, you have it. since your question was on percieved loudness, if your neighbors are like mine they will be comparing you to straight pipe Harleys, so there should be alot of leway.
 
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The decibels are used because the human ear hears it that way.

Hope everyone rides with ear plugs.
-Spaceman.
 

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Hey Q, this is off topic - but - that how stuff works site is really cool. I didn't know about it, thanx for the link.
 

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Robert:
You have to remember that in the example they are showing that 10db is 10 times louder that 0db & that 20db is 100 times & 30db is 1000 time louder. 20 doubles 10 & 30 triples 10.

That will be different @ the 80db, 90db, & 100 db range. 90 is not 10 times greater that 80 in anything. Yes, it is 10(in this case desiblels) greater but it is still only 10 steps louder. 80 isn't being doubled by 90 or even 100. 100db is 25% louder than 80db.

On a side note to help help you understand. In the audio world (car audio or home audio), it takes twice the amount of power to increase the volume by 3db. For example, if your stereo is playing @ 80 db with 100 watts of power from your amplifier. For you to increase the volume to 83db you will need to have 200 watts of power. So, now to get to 86db you will be needing 400 watts of power. For 89db you will need 800 watts of power & .........

I hope that helps.
 

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Actually to the human ear 8 to 10 dB sounds twice as load (or half in the other direction). The ear can just hear a 1 dB difference. In audio 10 dB is about 10 times the power (and still sounds twice as loud), 3 dB is twice the power, 6 dB is twice the voltage (4 X power).

As far as the slipons go, the first hypothetical can (90 dB) should sound twice as loud as stock to your ear, the second hypothetical can (100 dB) will sound four times as loud give or take a little. The other consideration is the audio frequency released form the cans, the lower the "tone" the farther the sound will travel.... In otherwords the bike will sound twice as loud at the bike but maybe 50' away may sound more then twice as loud as stock (at the same distance) since the stock muffler does not have as "deep" a tone. This is can be observed by listening to punks in Civics cranking the bass... Your neighbours may be more offended by the distance the sound travels then by the actual amount of sound that is leaving the can (hope that makes sense).
 

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Rob,
If you want them louder, drill the rivits out, slip em apart & get rid of some, more, most or all of the internal packing. it's amazing the different notes & degree of loudness you can obtain with changing in or out 20% of the packing.

PS : db's were explained to me like this......

if you have one 747 sitting on the tarmac idling away (if they actually do that) & it's pumping out 90db & you park an identical second plane beside it also pumping out 90db, how many db will you be exposed to?

180db is incorrect, you will be exposed to 93db.

just a different way of explaining it, much the same as the other guys have.
 

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Discussion Starter #14
Again, thanks all for helping me to understand.... By the way, I've ordered a set of Giannelli CF round high-mounts. Can't wait to get them!

Rob
 

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And if that's not confusing enough... open your airbox/remove the cover and the intake pulses rival the exhaust note.

I had a trusted neighbor ride my M900 around the block a few times so I could hear it as others do. I have unknown aftermarket cans (look like Ark from England maybe?) and no airbox lid/K&N. At low steady speeds the bike sounds louder coming toward me than going away. The intake pulse becomes a hammering noise at speed and I wear earplugs every ride now.

But boy, does that Ducati sound beat everything else! I have heard comments during televised races that riders definitely hear a Ducati coming up behind them and I don't doubt it.
 

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lucky for me I listened to headphones too loud growing up, and then there was the time in the Marines as a jet mech. I figure I lost enough hearing there, that the noise doesnt bug me all that much with a helmet on.
 
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