rabie Posted December 16, 2004 Report Share Posted December 16, 2004 Not actually having seen one in the flesh yet I can Quote Link to comment Share on other sites More sharing options...
neonsurge Posted December 16, 2004 Report Share Posted December 16, 2004 Trials is 92 db at 45 degree and 60cm at revs of cc via chart IIRC. Every centre is *supposed* to have noise meter operators and if the bike is too noisy exclude the rider (or impose other punishments - its up to the clerk of the course) But measuring the noise of a bike like this is meaningless in the context of what's being discussed. For example, say a 2-stroke tests at 90db and a 4-stroke tests at 87db. So the 4-stroke is quieter, right? Now perform the same test at 100m distance. The 4-stroke will test way, way higher than the 2-stroke. The key to all of this is the attenuation (decay) rate of the sound pressure wave and is (approximately) calculated as the square of the frequency (a = f^2). So a higher frequency sound decays exponentially faster (over a shorter distance) than a lower frequency sound. Remember it's unlikely that the kind of people who'll be complaining about the noise will be stood a couple of meters away from the bikes. It's the people in the houses half a mile away who'll only be hearing the "thump thump" of the 4-strokes who'll be on the 'phone to environmental health in the morning. The only solution is for manufacturers of 4-stroke bikes to concentrate of making those bike exponentially quieter than a (reference) 2-stroke. If this could be achieved, the 2006 model 4RT's exhaust note would still decay more slowly than that of (for example) a 270 Rev3, but due to the lower intensity of the pressure wave, the distance at which the sound becomes inaudible might be approximately the same. Unfortunately, current 4-stroke engine and exhaust design means that more noise = more power. Ye cannae change the laws of physics. Quote Link to comment Share on other sites More sharing options...
marky boy Posted December 16, 2004 Report Share Posted December 16, 2004 (edited) I was gonna say something sarcastic (4 a change ) but after reading that Neonsurge all i can say is...... boy does that my head hurt Edited December 16, 2004 by marky boy Quote Link to comment Share on other sites More sharing options...
craftypiggy Posted December 16, 2004 Report Share Posted December 16, 2004 I agree with Marky...............my head hurts Quote Link to comment Share on other sites More sharing options...
g4321 Posted December 16, 2004 Report Share Posted December 16, 2004 It's the people in the houses half a mile away who'll only be hearing the "thump thump" of the 4-strokes who'll be on the 'phone to environmental health in the morning. Do you honestly think that the Honda will be offensive 1/2 mile away? At a trial on Sunday I couldn't hear the Honda 1/2 mile away, nor could i hear any of the two strokes. A couple of hundred yards away yes but if that level of noise upsets anyone they would complain if a motor mower was used at the end of the street or if a farmer had the gall to plough his fields with a tractor.. Think about this - how many trials venues are that close to houses/people or have no shielding due to contours or vegetation (trees/bushes). There are always people who will moan at motorsport but I can't see the noise of this bike being seen as offensive and giving them more to moan about. A roadbike witrh an aftermarket exhaust roaring past your house at 2am in the morning, a 16 year old on a moped with 'race ' exhaust, a yob in a corsa (car) with open exhaust and loud stereo or a MX race (close by) may be considered offensive (I like road bikes & MX!) but a trial - NO! If you think the Honda is too loud the simple answer is don't buy one! I won't at the moment because it is far too expensive to throw down a rocky hillside and I can get as much enjoyment out of a bike which is 20 years old and is probably just as loud! Quote Link to comment Share on other sites More sharing options...
bikespace Posted December 16, 2004 Report Share Posted December 16, 2004 Remember it's unlikely that the kind of people who'll be complaining about the noise will be stood a couple of meters away from the bikes. The only solution is for manufacturers of 4-stroke bikes to concentrate of making those bike exponentially quieter than a (reference) 2-stroke. Option 2: Run trials much closer to the houses of those who are likely to complain??? Option 3: Attach a small Gazoo to the back of the Monty silencer. This will obviously increase the frequency and therfore increase potential attenuation. If you can glue enough gazoo's together you could possibly create the worlds first stealth bike, or at least get these whingers complaining about juvenile jazz bands instead of trials. Not sure how it will stand up to scientific scrutiny, but on the way back from the pub it seems fair. Quote Link to comment Share on other sites More sharing options...
neonsurge Posted December 17, 2004 Report Share Posted December 17, 2004 A roadbike witrh an aftermarket exhaust roaring past your house at 2am in the morning, a 16 year old on a moped with 'race ' exhaust, a yob in a corsa (car) with open exhaust and loud stereo or a MX race (close by) may be considered offensive (I like road bikes & MX!) but a trial - NO! I was talking about 2-strokes vs. 4-stroke in general. Sorry if that wasn't clear. A big part of the problem is that Joe Public doesn't know the difference between trials and MX. One noisy dirt bike = all dirt bikes are noisy and environmentally unfriendly and should therefore be banned. Whether you'd be able to hear the 4RT from half a mile away... well, I dunno and it depends on which way the wind is blowing but half a mile's not that far and I think you might be surprised. If you think the Honda is too loud the simple answer is don't buy one! I personally don't think the 4RT is too loud. I like the sound it makes. If I had the cash for a new bike, I might even buy one (although I think I'll wait to see what Beta come up with first). But (and this is my point), the laws of physics state that the noise from a 4-stroke engine will travel further than the noise of a 2-stroke. And it's the objective perception of noise that's the issue, isn't it? Option 3: Attach a small Gazoo to the back of the Monty silencer. This will obviously increase the frequency and therfore increase potential attenuation. If you can glue enough gazoo's together you could possibly create the worlds first stealth bike, or at least get these whingers complaining about juvenile jazz bands instead of trials. I like it. In fact I like it so much I think it ought to go into production immediately. Anyone want to buy a "Trials Trumpet"? Quote Link to comment Share on other sites More sharing options...
lastplacebrad Posted December 17, 2004 Report Share Posted December 17, 2004 :snowman: isn't a gazoo one of the things posh folk put in their back gardens to use at tea parties !!! i think he means kazoo ..... (yes i know shut up you tw*t ) Quote Link to comment Share on other sites More sharing options...
neonsurge Posted December 17, 2004 Report Share Posted December 17, 2004 isn't a gazoo one of the things posh folk put in their back gardens to use at tea parties !!! No, they're called "filthy peasants", also known as "servants". Oh, yeah: Shut up you t---! Quote Link to comment Share on other sites More sharing options...
stuessenhigh Posted December 17, 2004 Report Share Posted December 17, 2004 Doesnt one need vibration as well as air, for the kazzoo thing to work??..so we would need a bike that vibrates alot...(not a Beta of course..they're far too smooth ) I like the trials trumpet idea too...but that would definately need vibration and air. We can then blame all the noise on the local town band..cool!! Quote Link to comment Share on other sites More sharing options...
downunder Posted December 21, 2004 Report Share Posted December 21, 2004 The problem with the 4RT (and all 4-strokes) is not the "loudness" (the number of dbs shown on a sound level meter at a distance of 2 metres), it's the lower frequency of the exhaust note that travels further and penetrates solid objects more effectively. As has been pointed out, the Beta 270 is, purely in terms of dbs, louder than the Montesa but the shorter wavelength of the sound means that is decays far more quickly. Lower frequencies travel further. And that's the real problem, I think. The 4RT would have to be much quieter than the Beta for the noise to dissipate completely over the same distance. Hi All The issue of 4 stroke noise and 2 stroke noise is sound frequency. At a trial here in Australia earlier this year I had professional sound levels taken. Although no 4RT's have found there way here yet the results were quite interesting. Some of the highest noise levels @ 20m were generated by the normal run of the mill Gassers, Shercos and Beta's while at idle. The reason being is the noise at idle is a lower frequency than at revs. Even though the high rpm noise is louder in dBA it looses power faster over even short distances than the deeper pop pop at idle. The 4RT and any 4 stroke will have a noise that is more audible over a longer distance. This is why the 4RT can pass a sound test at similar levels to a 2 stroke but be more audible at a greater distance. BJdownunder Quote Link to comment Share on other sites More sharing options...
stuartc Posted December 28, 2004 Report Share Posted December 28, 2004 At our trial on 5th Dec this year we had a few strokers present, now I am NOT pointing the blame at them, however we had the 1st complaint about noise in 20 years and more at this venue. Only 3/4 houses within 3 miles. The venue is used EVERY weekend by trials folk practising !!! It has been used like that for umpteen years. Read from that what you will, the physics don't really come into it. It is what Mr & Mrs Anybody at No 3 hears, THAT is what comes into the equation !!!! Quote Link to comment Share on other sites More sharing options...
t-shock 250 Posted January 1, 2005 Report Share Posted January 1, 2005 (edited) There was one at our trial today, i was very surprised at how loud it was when the throttle was used, and not a nice 4 stroke sound either, very harsh, bit like an old cub or something without a tail pipe. Personally I would be really surprised if it passed the noise test, it was the only bike you could hear in the woods, i know people have been saying it's no worse than a 270 Beta but i can tell you it bloody well is! It definately carries a LOT further than a 2 stroke and this is where some clubs may start to encounter difficulties with land not situated in the middle of nowhere. Edited January 1, 2005 by t-shock 250 Quote Link to comment Share on other sites More sharing options...
marky g Posted January 1, 2005 Report Share Posted January 1, 2005 Saw one today at the local Shropshire Trial, sounded as quite as the two strokes, didn't speak to the guy to ask if he'd took any restrictors etc etc. nice looking bike Quote Link to comment Share on other sites More sharing options...
t-shock 250 Posted January 2, 2005 Report Share Posted January 2, 2005 Maybe the restrictors affect the noise quite a lot, don't know what restrictors were in this one, although the rider did say he regretted buying it, he used the word "*****" in fact. Quote Link to comment Share on other sites More sharing options...
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