How do tracks measure noise levels?

[Funkatronic]

been thinking about the track day in August and am concerned that my arrow full race exhausts will be too loud to let me ride

how would i go about measuring the noise level?

i know i need a dB meter (my iphone can oblige or i have some more serious audi test kit fom my sound engineering days) but how do the tracks go about measuring noise trackside?

is it measured 1 meter from the rear of the bike revved to 5000rpm in neutral??
do different tracks use different methods?

also what is the noise limit at Caldwell?

thanks in advance
ali

[CK & AK]

All race tracks have a max of 105db.
On occasions there are quiet days, which can mean down to 98db or less - check on the TD info before booking, as each track is different.
Cadwell is an MSV track, that will be 105 unless stated on the booking form.

Noise testing is done before you go on track at all MSV tracks & many others (some other tracks do 'on track' testing - like Donington which has noise metres overhead, Castle Combe have both - noise testing 1st & also on track meters too).
You usually take your bike to the designated place from about 8am on a TD to join the queue

MSV tracks follow the ACU regs to the letter (in our experience): (Long bit now from here: http://www.acu.org.uk/uploaded/docum...eSection11.pdf )
14.8.3 is what you want

14.8 Control of Exhaust Sound Level
1. The Clerk of the Course will disqualify any machine which exceeds the maximum permitted sound level, or which in his opinion is deemed to be excessively noisy. An official sound level test results form will be completed at each meeting and will be submitted by the Clerk of the Course to the Stewards of the meeting.
2. Noise limit in force for all machines is a maximum of 105dB/A. For testing the fixed RPM specified in 6 below will be used.
3. The noise test will be conducted with the microphone placed at 50 cm from the exhaust pipe at an angle of 45° measured from the centre-line of the exhaust end and at the height of the exhaust pipe, but at least 20 cm above the ground. If this is not possible, the measurement can be taken at 45° upwards.
4. During a noise test, machines not equipped with a gear box neutral must be placed on a stand.
5. The driver shall keep his engine running out of gear and shall increase the engine speed until it reaches the specified Revolutions Per Minute (RPM). Measurements must be taken when the specified RPM is reached.
6. Due to the similarity of the piston stroke in different engine configurations within the capacity classes, the noise test will be conducted at a fixed RPM. For reference only, the mean piston speed at which the noise test is conducted, is calculated at 13 m/sec (2-stroke engines) and 11 m/sec (4-stroke engines).
Sports Production and Sports Production based engines:
1 cylinder 2 cylinder 3 cylinder 4 cylinder
250cc (4-stroke) 5,500 RPM 8,500 RPM
400cc (4-stroke) 5,000 RPM 6,500 RPM 7,000 RPM 8,000 RPM
600cc (4-stroke) 5,000 RPM 5,500 RPM 6,500 RPM 7,000 RPM
750cc (4-stroke) 5,000 RPM 5,500 RPM 6,500 RPM 7,000 RPM
Over 750cc (4-stroke) 4,500 RPM 5,000 RPM 5,000 RPM 5,500 RPM


There is more on the rules page, but basically your monster has to be checked at 5000 rpm.

[Funkatronic]

awesome and super thorough answer

thanks loads, thats exactly what i needed

CK & AK

In your experience will a set of full 50mm termis pass?

I thought they asked a new arrival to the village if she had to turn the sound up while watching the Eastenders omnibus. If yes, the bikes are too loud and will have to be banned. If not, they'll go to another house.

I have been wrong before, though.

[CK & AK]

Originally Posted by PDL

CK & AK

In your experience will a set of full 50mm termis pass?

iffy - you could get lucky & many have been, but if I was you - rather than run the risk of being possibly borderline - I'd pop baffles in to start with.
That said, our 1098s on 70mm passes at 105 dead on with no baffles, but it does have some damned good cans on it (non-termi's).
The M800 makes 102 without baffles but with its full race system - with baffles it makes 96 +/-

[slob]

...and pull the lever in during the noise test of you have an open/dry clutch, every little helps.

...and warm the engine up first

[CK & AK]

Originally Posted by Gilps

...and warm the engine up first

Most definately Gilps - really warm

[J.P]

At the MSV date's I've done they actually incert a probe into the exhaust rather than just listen to the end of it. The Cadwell date you're on about is 105 db's limit and it a track rule not the company so if it don't pass, it don't get in. My bike is very loud, and hits 105 db's every time, BUT i do have a set of baffle's to put in IF it doesn't make it.

[LouSCannon]

I was just going to take a set of DB killers just in case...