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Decibel Meter


Paul H
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My car has been noise tested by CMC rally scrutineering at 96db at 1 metre, and at Goodwood at "less than 98db", at 1 metre.  I understand that.

But I'm a bit confused with db levels in practical use.  I know that in audio electronics an increase of 3db is a 100% increase in level, a doubling of amplitude, but this does not mean that it is twice as loud in audio terms. Why is that? If a 3db increase gives you 100% more amplitude why is it not audibly twice as loud? 

 

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7 minutes ago, dougbgt6 said:

I blame the Quo.

Saw them perform last century. It was after their hit Pictures of Matchstick men. I used to go to a pub on the Fulham Road in London at the weekends, free group but expensive and terrible beer! The regulars were all rock/ heavy metal fans, so there was a collective groan when they were announced. After their first number the response was much better!

A 'bad' group weren't booed, there was just a couple of seconds silence at the end of a number then the chattering started up . .

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Ah yes, you are correct Doug.  Human hearing is not linear, but something like a logarithmic curve, so it would be a much higher multiplication factor that would sound twice as loud, and therefore a larger increase than +3db.

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2 hours ago, Chris A said:

I used to go to a pub on the Fulham Road in London at the weekends,

The Greyhound? I used to go there! Dreadful Bands, unpleasant beer, but pretty girls. We kept going back, for some reason.

Doug

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1 hour ago, dougbgt6 said:

The Greyhound? I used to go there! Dreadful Bands, unpleasant beer, but pretty girls. We kept going back, for some reason.

Doug

I can't deny it. 😒

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On 05/07/2021 at 15:35, JohnD said:

I have a "real" sound meter, and inside my race Vitesse, which is stripped of all potentially sound deadening trim, I get 98dB.   It's so loud in there that I wear ear defenders while driving it on the road, without a helmet.   Otherwise .... sorry, what did you say?   That level of noise is equivalent to standing next to a chain saw, and it WILL damage your hearing after just a few hours exposure!  That's why tree surgeons wear defenders!

The legal limit at the roadside is 74dB.    The limit on the race track is 93db at 2 metres

100dB inside a road-going, fully trimmed car?   I don't think so.  Or I hope not, for their ears sake!

John

Surely the limit depends on the track? I'm sure at Mira the limit was 98db (antilag not allowed) - other venues are 100db - and Le Mans was higher than that - so the BMW M whatever rear engined car could run with basically 2 3" or 4" pipes off the manifold through the turbos and out the back - they had another exhaust for noise limited tracks that apparently twisted around the engine bay to get the silencers in and also robbed them of a measurable amount of power.

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I'm quoting MotorsportUK competiton regulations, Anglefire, which apply to any circuit, stage or other venue in the UK that operates to their regs.

 See the Blue Book (The Yearbook) Section J, page 153, Chart 5.18: https://www.motorsportuk.org/wp-content/uploads/2019/12/145-154-Vehicles-J.pdf

image.png.49ecf9290444102e2cc0f6bad085c3fb.png

 

I don't know anything about noise regulation in France, but MIRA doesn't run to Motorsport regs.

JOhn

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9 hours ago, JohnD said:

I'm quoting MotorsportUK competiton regulations, Anglefire, which apply to any circuit, stage or other venue in the UK that operates to their regs.

 See the Blue Book (The Yearbook) Section J, page 153, Chart 5.18: https://www.motorsportuk.org/wp-content/uploads/2019/12/145-154-Vehicles-J.pdf

I don't know anything about noise regulation in France, 

JOhn

Probably 3 levels of acceptability:

1. Quick shrug of shoulders : All ok

2. Long shrug of shoulders : OK, but at the limit

3. Long shrug of shoulders & forearms extended with palms of hands facing up: Putain!

 

 

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