Is my loud ex­haust p*ss­ing off the neigh­bours?

Vance & Hines risks get­ting the net cur­tains twitch­ing

Motorcycle News (UK) - - Garage -

As I get older I’m be­com­ing in­creas­ingly sen­si­tive to noise pol­lu­tion. I live on a very quiet hous­ing es­tate with some very good neigh­bours so I’m keen that my “noisy mo­tor­bikes” don’t up­set the sta­tus quo. A lad with his Citroen Saxo and go­daw­ful

six-inch tail pipe raises my hack­les every time he drives past the house and I don’t want my neigh­bours to feel the same way about me with my Vance & Hines two-into-one pipe on the Street Twin.

On the other hand, noise is a very im­por­tant part of mo­tor­cy­cling. Be­ing able to hear the ma­chine work­ing is cru­cial to the en­joy­ment and, judg­ing by how many other af­ter­mar­ket ex­hausts are sold in the UK, I’m not alone (on­line re­tailer sports­bikeshop.co.uk sell more than 600 a year). The stan­dard twointo-two ex­hausts on the Street Twin are whis­per-quiet and make the bike feel, well, a bit wimpy. It’s a 900cc twin and it needs to sound like one.

The Vance & Hines high-level pipe is an of­fi­cial Tri­umph part (£1150) but is sold for ‘off-road use only’. When the pipe was fit­ted as part of Tri­umph’s Scrambler In­spi­ra­tion pack for the Austin Vince Twin Shock event I en­tered in Spain last month I was

ini­tially ner­vous of how loud it was go­ing to be. A pass­ing com­ment by one my neigh­bours about my “noisy mo­tor­bikes” has en­cour­aged me to do some re­search.

Sound is mea­sured in deci­bels, a sys­tem that’s log­a­rith­mic not lin­ear. The small­est au­di­ble sound is 0db. A sound 10 times more pow­er­ful is 10db and one that’s 100 times more pow­er­ful than near si­lence is 20db. If a sound is 1000 times more pow­er­ful it reg­is­ters 30db. So as you can see, when sound is mea­sured in iso­la­tion it’s dif­fi­cult to tell just how noisy some­thing is. But with a cheap sound me­ter and few com­par­a­tive mea­sure­ments it’s much eas­ier to gauge how likely I am to cause up­set.

All my mea­sure­ments were taken two me­tres from a static noise sources (the ex­haust) and 20m away from mov­ing sources, at a 90-de­gree an­gle. It’s the same method cir­cuits such as Snet­ter­ton use when as­sess­ing sound lev­els on track­days. The am­bi­ent sound level out­side my house is 37.5DBA (the ‘A’ de­notes a weighted mea­sure­ment that mim­ics the rel­a­tive loud­ness of sounds as per­ceived by the ear).

At tick­over my 2006 Honda Civic car peaks at a very low 50.4DBA, a con­ver­sa­tion be­tween two peo­ple in the street hits 59.5. In con­trast, my 150cc Briggs and Strat­ton lawn­mower peaks at 93.3 (the lawn­mower has no throt­tle con­trol).

At tick­over the Street Twin peaks at 77.5DBA, ob­vi­ously higher than the car’s tick­over but way be­low the 150cc lawn­mower and it’s not un­til I blip the throt­tle of the Street Twin vig­or­ously that I get the sound level me­ter to rise above 90DBA.

Drive-by mea­sure­ments tell a sim­i­lar story. At 20 me­tres dis­tance the lawn­mower still reg­is­ters 86.1DBA and the Civic 61.4 (while do­ing 20mph). In a third gear drive-by the Street Twin reg­is­ters just 78.6. So while the Street Twin is nois­ier than my car, it’s qui­eter than the lawn­mower and pro­vid­ing I don’t rev the bike as I’m leav­ing the es­tate, I’m pretty con­fi­dent me and the neigh­bours will get along just fine.

‘A lad with his Citroen Saxo and go­daw­ful six-inch tail pipe raises my hack­les every time’

Stan­dard pipe looks nice enough but is barely a whis­per

Beefy Vance & Hines looks ma­cho but is it just too loud?

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