Having just been sound tested at 108,5 db I NEED TO MODIFY MY EXHAUSTS (MUFFLERS).does anyone know of a good system and meter to check the levels. The track insisted that testing was at 4500 rpm so as you guessed I wasnt able to test the car.Already have the bundle of snakes ,Its the boxes that I need to look in to
good priced decibel meter
- Thread starter HUW PEPLOW
- Start date
yep got the same app but wasn't sure it was accurate
Seymour Snerd
Lifetime Supporter
In the US we have an electronics chain store Radio Shack which sells a ~$50 unit that would be good enough. http://www.radioshack.com/product/index.jsp?productId=2103667&CAWELAID=107593122
However, suspecting you can't easily get those over there, the next level up in quality is Extech which I see on Amazon for $90.
http://www.amazon.com/Extech-407730-130-Decibel-Digital-Sound/dp/B000EWY67W
Tandy = Radio Shack
You might want to talk with the track's Chief of Sound / Tech...
I can tell you from my experience with the SCCA that there are many different factors and inputs to measure than just a DB reading on any meter.
Wind, Temperature, track surface, length of the grass (I am not joking) all play a role.. There are also different weighting settings that need to be used.
Now to your exhaust system.
You might want to consider adding a balance pipe between the two collectors. This way the individual exhaust pulses are split (pressure wise) between both mufflers.
I can tell you from my experience with the SCCA that there are many different factors and inputs to measure than just a DB reading on any meter.
Wind, Temperature, track surface, length of the grass (I am not joking) all play a role.. There are also different weighting settings that need to be used.
Now to your exhaust system.
You might want to consider adding a balance pipe between the two collectors. This way the individual exhaust pulses are split (pressure wise) between both mufflers.
Seymour Snerd
Lifetime Supporter
Randy raises a good point. Ideally you should measure it at the same track with the meter in the same position as there's. Second best is to have a written standard for how the measurements is to be taken (so many feet away, car going in such and such a relative direction, microphone at height x, etc.) Otherwise you may think you've fixed it base on a measurement at home and then get to the track only to be disappointed. Sound is a four-dimensional phenomenon and it's really hard to reproduce a measurement in a different physical environment.
In the UK motor sport is governed by the MSA they have a rule book known as the Blue Book. The content is available on line. It is almost certain that the Blue Book defines how the sound test sould be done. Even if your visit to the track is not for an event the odds are they will follow the Blue Book in how the test is conducted.
Most of tracks in germany and austria are noise level controlled.
They have some exception days.
Anyway usually they don´t do static measurements. They measure on the track
( for example on SALZBURGRING on the long straight where you are usually WOT i high RPM´S).
So the only way to improve is to do relative measurements. If you fail on track and they tell you how much you have been over than try to reduce at least the same percential factor on your statuc measurement.
My conclusion. I will go to eastern europe tracks, where you are still allowed to run megs. ( also the tracks are very nice and more cost friendly)
TOM
They have some exception days.
Anyway usually they don´t do static measurements. They measure on the track
( for example on SALZBURGRING on the long straight where you are usually WOT i high RPM´S).
So the only way to improve is to do relative measurements. If you fail on track and they tell you how much you have been over than try to reduce at least the same percential factor on your statuc measurement.
My conclusion. I will go to eastern europe tracks, where you are still allowed to run megs. ( also the tracks are very nice and more cost friendly)
TOM
Hi.
Try this vendor on ebay. I just bought one last month and it arrived here iin the UK with me from HK after only 5 days. Item ref 260796203902. Cant see any others listed at present but I am asure they have more. Works a treat. Up to 130dB c/w a 'max dB' setting so you can test it by yourself from the safety of the cockpit without getting you ears blasted or suffering CO poisoning!.
With the straight through megs and with rpm at 75% of max and holding the device at a distance of 1m from tailpipes (without any obstructions behind to cause any echo) gave a reading of 120.6dB at 3000rpm and 121.8dB @4000rpm. OUCH !!!
Try this vendor on ebay. I just bought one last month and it arrived here iin the UK with me from HK after only 5 days. Item ref 260796203902. Cant see any others listed at present but I am asure they have more. Works a treat. Up to 130dB c/w a 'max dB' setting so you can test it by yourself from the safety of the cockpit without getting you ears blasted or suffering CO poisoning!.
With the straight through megs and with rpm at 75% of max and holding the device at a distance of 1m from tailpipes (without any obstructions behind to cause any echo) gave a reading of 120.6dB at 3000rpm and 121.8dB @4000rpm. OUCH !!!
Hi Huw
car builders sell one about £20 Andy
car builders sell one about £20 Andy
You never tell the sound tester the true max RPM for this exact reason.
I've been race engineering a motorbike engined sportscar this season and at times we've had to tell the the max was 4,000 rpm off the limit to squeeze in under the limit. But interestingly what was causing the problem was over fuelling when cold and it running slightly rough. The crackles etc pushed the noise over 108 dB. When the engine was hot and had been cleared out completely it was comfortably under 105.
We did go testing alongside a Cobra with a tuned 351 and he had real trouble, in the end he stuffed some rags up the pipe for the noise test and got through.
I think Maplins sell good cheap meters.
I've been race engineering a motorbike engined sportscar this season and at times we've had to tell the the max was 4,000 rpm off the limit to squeeze in under the limit. But interestingly what was causing the problem was over fuelling when cold and it running slightly rough. The crackles etc pushed the noise over 108 dB. When the engine was hot and had been cleared out completely it was comfortably under 105.
We did go testing alongside a Cobra with a tuned 351 and he had real trouble, in the end he stuffed some rags up the pipe for the noise test and got through.
I think Maplins sell good cheap meters.
It really depends on the background noise. I've had accurate readings most of the time but some really wrong ones every now and then. :laugh:
________________________________
Steve Works
sound level meter
Howard Jones
Supporter
I am the Calibration Tech for my employer. We have both Radio Shack and Simpson sound level meters. The Simpson is pricey....like 1.2K+ (US). Radio Shack is far less expensive but doesn't have the same measuring capabilities as the Simpson.
Both are good units. In 15 years of maintaining them I have yet to have one fail annual calibration checks.
And as others have stated, find out all the noise requirements and how the readings are to be taken. Many factors can alter the readings.
Both are good units. In 15 years of maintaining them I have yet to have one fail annual calibration checks.
And as others have stated, find out all the noise requirements and how the readings are to be taken. Many factors can alter the readings.
