Top Gear Exhaust Comment

Hi guys,
as an electronic engineer I can perhaps comment on the use of decibels here. The scale of dB is not linear but natural logrythmic.

There are two different uses for the use of dB (decibels) which people often get confused. The first is attenuation of an amplifier. Whereby "0dB" is on full power and then "minus infinity dB" is silent.

And the measurement of noise levels. Which are taken as a ratio of the current measured noise (e.g. exhaust noise) against the quietest sound a human ear could hear (traditionally a candle burning).

Noise is basically sound pressure, and is dependent upon proximity of the sensor to the noise source and possible reinforcement due to confinement. Therefore an exhaust note tested in a passage would make a higher dB reading than one in a featureless desert.
This is the same as a 500w sound system being lost in a stadium, where it would be deafening in a car.

Human hearing is not linear but logrithmic, and so twice the volume in a sound system requires 10 times the wattage of output power. And at that stage, the dB measured would theoretically increase by 3dB.

Because an exhaust pipe is in effect an inverse amplifier, it would be possible to line up a row of different exhaust configurations and give them all a "negative dB rating" which shows how much quieter the pipe is at say 9000 rpm than no exhaust measured at one meter from the back wheel.

This in my view would be a useful and relevent experiment as then you would be comparing like with like, as you would use the same bike and the same test site.

However, laymen are used to the "noise level decibel" so they can compare the overall noise level to the regularly published noise levels for hairdriers, jet engines perforated eardrums, shattering concrete and Motorhead.

I'll get my coat...

Now we have an ally on Top Gear with the news that Richard Hammond has been signed up to write for MCN

So even more crap will be available to read in MCN :P

Originally Posted by muddycoffee

However, laymen are used to the "noise level decibel" so they can compare the overall noise level to the regularly published noise levels for hairdriers, jet engines perforated eardrums, shattering concrete and Motorhead.

Out of interest whats the loudest Motorhead have been recorded at? AFAIK Manowar held the loudest band title for a while, if not still, at a rocking 129.5 decibels....

and people wonder why I dont bother with earplugs anymore...

[Biker Biggles]

I once worked on a Slade gig when they played a hall no bigger than Dingwalls with a 17000 watt pa.Cum on feel the noiz. I could'nt hear for days

[northwind]

Yup, Prosound say the same about Manowar- though it's also often said that Maiden at Donington in 88 were the loudest. These days you can make much more of a racket with much less gear (seen the rigs they use at festivals this year? Weeny...) but because of tighter health and safety lawsthey don't get used to their full potential- the cowards!

Originally Posted by lynw

wheres Northwind? he posted that on visordown, though I reckon him saying its got as much chance of becoming law than him getting through next year without crashing was a bit harsh on himself

Spies! Spies everywhere! It's true though, it's just like that child pillion bill from easrlier this year- no realistic chance of becoming law whatsoever, but it gets reported as if it were inevitable.

Some bland AOR band in america are said to hold the "loudness at a gig" record with 160db apparently, but if Norris McWhirter and Roy Castle haven't said it's ok, it doesn't count as far as I'm concerned.

It is much easier to get extremely loud amplification these days, latest developments of digital psu amps have allowed 2000w amplifier units to be extremely small and light, similar to 2 laptop PCs on top of each other when once a 800w amp was as heavy as a barrel full of bricks.
Chameleon Amplifier_Only 13Kg 650W per channel

Bloody Heavy old school amplifier_35Kg 400W per channel

Originally Posted by muddycoffee

Some bland AOR band in america are said to hold the "loudness at a gig" record with 160db apparently, but if Norris McWhirter and Roy Castle haven't said it's ok, it doesn't count as far as I'm concerned.

PMSL

Um, am I the only one that finds this a bit sick?

Originally Posted by northwind

Yup, Prosound say the same about Manowar- though it's also often said that Maiden at Donington in 88 were the loudest. These days you can make much more of a racket with much less gear (seen the rigs they use at festivals this year? Weeny...) but because of tighter health and safety lawsthey don't get used to their full potential- the cowards!

I reckon if Manowar lost the record theyd just go to Brazil to get it back.... they got such a huge following there and I doubt the Brazillian government would care too much about noise level somehow

anyone up for Rock in Rio sometime?