Cal Club Autocross Forums

Jayson Woodruff wrote:Nothing says where you have to be. This sound is measured in 1sec averages ("slow" setting), which means the sound you're making as you pass the meter typically won't show up on the meter for 1+ seconds, which at 60mph is 80ft later.

Jay W

Jeff Wong wrote:When taking readings from the sound meter, is it only valid when the car is directly in front of the meter? I know our car lined up with the sound meter only read 90db, when we passed the sound meter is when we acutally got the violation.

Thanks Jason, I should really read those rules.

Stacey, Tadd, and I will be running a rental Prius in ST/STL for the Tour.

I'm making the gamble that we'll be the only car that passes sound...

Steve Ekstrand wrote:Stacey, Tadd, and I will be running a rental Prius in ST/STL for the Tour.

I'm making the gamble that we'll be the only car that passes sound...

good... should be faster than your civic anyway

Don't get so caught up in trying to figure sound readings.
The sound meter is calibrated and reads correctly.
It is always placed 50' from the edge of the course.
The variable here is the location of the sound meter on course.
Weather (cloudy, clear) also plays a smaller factor.

When the meter is placed in an unfavorable position (such as Sunday) higher readings will always be found.
A stock C6 Z06 should not be over sound.

The good news is that the location of the meter for the tour will be in a much more visitor friendly (but still rule compliant) location.

That corvette if it was truly unmodified, should have been 85db under a testing protocol that should read HIGHER than SDR's.

Sounds like the failing last weekend was with COMMON SENSE!

Mark Duerst wrote: A stock C6 Z06 should not be over sound.

The stock C6Z has a set of vacuum actuated flaps that basically turn the exhaust into a strait system under load, which is loud. The standard C6 also has an optional factory exhaust that is right up there with the loudest of the aftermarket stuff. I would not be surprised to see either of these over the limit in SD.

The C5Z guys with Borla and Corsa systems have always been on the edge, and often over.

Leonard Cachola wrote:

Jamie Lessie wrote: Thanks Leonard!

Hope you had a good time, I sure did! Are you sore today? lol

Not as sore as I thought I'd be, but yeah I totally had fun and have been telling everyone at work today about my experience driving your car! :gpower:

Glad you had a good time! Hopefully we will see you at El Toro on the 4th!

But this wasn't about any particular car. Cars are too loud at SD all the time. Obviously, this weekend something went wrong! Cars were often 10db louder than in past SD experiences. It wasn't isolated it was across tons of different cars at different points in the day.

Jason Isley BS RX8 wrote:

Mark Duerst wrote: A stock C6 Z06 should not be over sound.

The stock C6Z has a set of vacuum actuated flaps that basically turn the exhaust into a strait system under load, which is loud. The standard C6 also has an optional factory exhaust that is right up there with the loudest of the aftermarket stuff. I would not be surprised to see either of these over the limit in SD.

The C5Z guys with Borla and Corsa systems have always been on the edge, and often over.

That one Borla system that is actually lighter than the factory C5Z titanium system (because there are tiny resonators only) is quite loud. Other than that one, we have never had a stock class C5Z or C6 over the limit. Even My old ASP car (now Berry's), was over only on occasion with the factory titanium mufflers, but it has headers, light 3" pipe and no cats at all.

I worked the trailer in the afternoon, and they called in Richard C. in his C6 as significantly over. He runs there every event, and has never been a problem before. Atmospheric conditions (particularly wind direction) and placement have a huge effect on readings, unfortunately.

I think they are just trying to scare everyone before the Tour so that you all add sound deadening before hand rather than them constantly watching people make changes during the event. Tricky tricky.



(PS. Gary, we sold the ASP car, it lives in Illinois now)

We used my iPhone DB Meter application ($1.99) to check Pete's CR S2K at El Toro. We were closer then 50' and were just over without the add-on restrictor to his tail pipe, and just under with the added "cork." Hopefully he'll be OK without it at the Tour.

Regarding the accuracy of the iPhone Decibel application, our tests so far has shown excellent agreement between professional sound level meters and the iPhone application (less variation than +- 2dB) when fed by a calibrated white noise source.

We hope you will enjoy your purchase!

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