• Protip: Profile posts are public! Use Conversations to message other members privately. Everyone can see the content of a profile post.

Stock Exhaust Sound - dbA - of 91 NSX

Joined
8 April 2004
Messages
3,004
Location
Edmonton, Alberta
Here are the sound readings taken 10 feet from behind the rear of my car.
I have 94,000 miles on this totally stock, engine & exhaust wise, car.
Car was stationary.
I just thought people might want to know and might use this as a reference.
Trev
The instrument used is as follows:
Bruel & Kjaer Precision Integrating Sound Level Meter Type 2230
Measurements where taken as SPL, RMS, A weighted, Frontal Sound Incidence.

RPM------10' OUT BACK-----INSIDE CAR AT EAR LEVEL
IDLE------61dbA------------51dbA
3000------74 dbA-----------60 dbA
5000------84 dbA-----------71 dbA
7000------93 dbA-----------81 dbA
 
I was doing some extensive readings during the day on a noisy paint booth fan and a Oskar welding fume arm system I supplied to a shop and found no real difference at what angle I was at but then again the noise was radiating out in all directions in a free field so............ Results could be a little quieter at 45 deg. for sure, but at ten feet, probably not much.
Trev
 
At those readings, a stock NSX wouldn't pass the current 90 db max set at Laguna Seca for normal track schools. They're getting pretty lousy about making it that low so that even a stock car, and the NSX isn't the only problem car, can't pass the sound level they set. Now if you're IRL, or CART or a big name venue running an event, then those levels are never brought out. Seems money overrides any real concerns about noise control. :mad:
 
ATERPAK said:
At those readings, a stock NSX wouldn't pass the current 90 db max set at Laguna Seca for normal track schools. They're getting pretty lousy about making it that low so that even a stock car, and the NSX isn't the only problem car, can't pass the sound level they set. Now if you're IRL, or CART or a big name venue running an event, then those levels are never brought out. Seems money overrides any real concerns about noise control. :mad:

The microphones/decibel meters at Laguna Seca are probably more than 10 feet away from the car.
 
They are but we are hearing that a lot more cars are having problems passing their sound restrictions lately. They're getting lower and lower with no real justification. :frown:
 
Double the distance and subtract 3 dbA!
So double from 10' to 20' and idle is 58.
Double 20' to 40' and idle would be 55.
Just a rule of thumb!
Dr. Tre
 
Didn't know the OEM exhaust make much sound...

I think it's not the exhaust that makes the sound but the engine itself.

Very interesting measures. Do you have the SPL at ear at WOT?
 
Its the exhaust that makes the noise when I am behind the car for sure.
I only had the sound meter rented for that day and thats all I measured.
I since had cored out two stock exhaust with a increase in noise but nothing I was looking for.
I now have a flowmaster and its the bomb!!!
Trev
 
My stock exhaust got up to 106dba on the dyno. Nothing too scientific. I was holding the meter at hip level, standing just to the side of the car. Maybe 5' max tip to meter? I recorded in rough 1000RPM increments but I don't have the numers with me.
 
Cool, that would be the best place to test sound, on a dyno so the engine is under controlable and sustainable rpm and load.
And just like the different readings we get with different dyno's, testing sound is a strange thing in itself. So many different reading, setting and factors.
Post what you got when you get them.
Always interesting.
Trev
 
My stock exhaust got up to 106dba on the dyno. Nothing too scientific.

Don't you have very much noise of the wires on the dyno. I recall a dyno of a stock NSX where you coudn't hear the exhaust note at all.
 
Back
Top