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Here is the sound level data from the New York ProSolo. Some of the sheets were hard to read and hard to understand and a couple of workers didn't get every car so as you can tell in the data not every car has all of their runs in it.

http://www.sccabb.com/sccabc/uploads/bharmer/2008-08-11_154127_2008_Seneca_PS_Sound_Level.xls

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Brian Harmer
SCCA Solo Technical Specialist
Solo National Rules: http://www.scca.com/documents/Solo_Rules/2010_scca_solo_rules.pdf

Running without mufflers was allowed.  I had no muffler for that event.

 

 

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Jim

"Those are my principles, and if you don't like them ... well, I have others." -Groucho Marx

do you happen to know the what distance these readings were taken from?

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Scott
#187 ES
95R Miata
07 Mazdaspeed 3 (for sale!)

The mic was setup to how it is specified on page 258-259 in the 2008 Solo Rules.

"Measurement will be taken at a point on course where the car can reasonably be expected to be at full throttle, under load, and at high RPM."

"The measuring point will be 50 ft from the edge of the course lane, using a coned gate as a reference."

"The meter will be mounted on a tripod, 3-4 feet above ground level."

"The meter will be positioned perpendicular to the vehicle's direction of travel."

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Brian Harmer
SCCA Solo Technical Specialist
Solo National Rules: http://www.scca.com/documents/Solo_Rules/2010_scca_solo_rules.pdf

Was the mic repositioned for Sunday's runs?  Or would different readings be due to weather conditions or something.  It seems for many cars the readings were higher by as much as 10 db.  I know we didn't change anything on our car.

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Mike Snyder (little)
STS 177 (pros)
SMF 142 (locals)

fastford16:

Was the mic repositioned for Sunday's runs?  Or would different readings be due to weather conditions or something.  It seems for many cars the readings were higher by as much as 10 db.  I know we didn't change anything on our car.

 

I don't beleive the mic was moved but a lot of things can be a factor in the change. The biggest would be weather but also factor in that sunday was runs 7-9 for everyone which meant they knew the course better and so they were able to give it better drive through it. That means on the gas more which also mean higher RPM and different sound level. Many things could be a factor in the differences.

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Brian Harmer
SCCA Solo Technical Specialist
Solo National Rules: http://www.scca.com/documents/Solo_Rules/2010_scca_solo_rules.pdf

That's interesting...

A C5 Z06 without mufflers was recorded at 95db, while a C6 Z51 with stock mufflers was recorded at 92db....

I'm not sure that any measurement technique is going to be very consistant or useful.  On Sunday the dbs seemed to be 10db higher.

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Ted

2003 C5 AE Coupe AS
2004 Z16/Z06 SS

The readings are interesting. My car (FMod #96) registered 104-106db at the NY Pro. Readings are regularly taken at all roadraces and my car has never been recorded over 98db.

-Jeff Blumenthal 

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- Jeff Blumenthal
FMod #96

Maybe the sound level meter was inadvertently set to an incorrect mode?  Such as using the wrong weighting.  Normally the A Scale should be used.  Here is a graph indicating weightings...as you can see that alone could easily lead to a 10dB change while the cars/driving stayed constant:

bharmer:

I don't beleive the mic was moved

I think it was out in the middle of the course Saturday, and closer to the finish on Sunday. Maybe someone who was working sound (or course in that area) can confirm? I tried to gather photographic evidence but it is somewhat inconclusive.

Saturday mid-course (see tripod in background)

Sunday, same general area, though it could be cut off

Saturday near the finish, no tripod in background

Sunday, tripod near finish (caution, huge pic) 

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Marnie // 99 Civic // 97 Legacy // 90 CRX Si // #116 // Finger Lakes Region SCCA

solo2racer14:

The readings are interesting. My car (FMod #96) registered 104-106db at the NY Pro. Readings are regularly taken at all roadraces and my car has never been recorded over 98db.

-Jeff Blumenthal 

Likely a matter of distance.  

ChrisFranson:

solo2racer14:

The readings are interesting. My car (FMod #96) registered 104-106db at the NY Pro. Readings are regularly taken at all roadraces and my car has never been recorded over 98db.

-Jeff Blumenthal 

Likely a matter of distance.  

 

Well in the absence of reflecting surfaces such as a huge cement building very nearby sound tends to diminish with distance fairly predictably.  Of course some frequencies can travel further (lower freqs) but an 8 dB change as noted seems pretty large.  Maybe one reading involved training...brief sounds such as a tire screech, fender liner rub, blowoff valve whoosh are allowed to go over the limit per the rules IIRC and that is fine.  Maybe a time weighting filter besides the frequency filters would reduce the need for training and the subsequent inexplicably different readings. 

bharmer:

fastford16:

Was the mic repositioned for Sunday's runs?  Or would different readings be due to weather conditions or something.  It seems for many cars the readings were higher by as much as 10 db.  I know we didn't change anything on our car.

 

I don't beleive the mic was moved but a lot of things can be a factor in the change. The biggest would be weather but also factor in that sunday was runs 7-9 for everyone which meant they knew the course better and so they were able to give it better drive through it. That means on the gas more which also mean higher RPM and different sound level. Many things could be a factor in the differences.

My Sunday runs were not substantially faster than my Saturday runs, yet my db readings were way higher on Sunday.  So I'm not buying the "know the course better" explanation.  I can even produce datalogs which back that up, with speeds and acceleration rates.

Since there appears to be photographic evidence that the meter was moved, this is probably a great set of data points on how the same cars can produce very different results depending on location of meter.  IMO, I'm glad to see that this kind of data is being looked at.  Any sort of policy based on this type of metering needs to take into consideration such variation.  Otherwise, plenty of cars that might be perfectly within limits on Day One, might be over the limit on Day Two, without changing a thing on their car.  Nobody likes surprises.

--Andy 

solo2racer14:

The readings are interesting. My car (FMod #96) registered 104-106db at the NY Pro. Readings are regularly taken at all roadraces and my car has never been recorded over 98db.

-Jeff Blumenthal 

 

10db was automatically added for it being an FMod.