Decibel readings from various exhausts

[David Buschur]

O.K. back to the DB testing.

After it being pointed out to me that there was a standard way to do the testing I am starting over. We are now testing various exhausts here using the SAE1169 method.

This method is done at a 45 degree angle to the exhaust tip and 20" back. The test is done at 4500 rpm on EVO's.

Each title in this post will be for the particular system tested.

David Buschur

[kmcconn9]

I didnt know there was such a specific standard for this type of testing..great info!

It will be interesting to see how different exhausts stack up..

[David Buschur]

This testing is baffling to me. So, I went into our lunch room and shut the door. The only thing in there is a large Pepsi machine and the fan on it was running. To me this is a VERY quiet room, very quiet. No other noises that I could detect. The decibels (DB's) in this room were 54 db's.

That will give you an idea. I don't fully understand this. If I hold my hand over the end of the meter at tight as I can it still reads around 53 db's. To me that should be 0 but maybe I am not grasping the concept.

David Buschur

[David Buschur]

2006 EVO9, BR350 #013.

2.5" downpipe
3" catback with Magnaflow muffler
Stock cat
272 exhaust cam
Ported manifold, 02 housing and 10.5 turbine housing.

1,000 rpm 79.1 db's
4,500 rpm 89.4 db's

David Buschur

[David Buschur]

2004 EVO RS. My car. Very nasty.

This car has every single mod we offer.

Revolver cams
Ported head
Built bottom end
Ported/coated manifold
Ported/coated 10.5 housing
Coated SS 02 housing
BR EVO9-5

Full 3" turbo back, V-band style, bullet muffler

These are all things that will effect how much noise the exhaust makes.

My car idles at 1200 rpm, this is where it idles the smoothest with these very large cams.

1200 rpm, 94.2 db's
4500 rpm, 107 db's

[David Buschur]

My brothers car.

272 cams.
Ported manifold
SS 02 housing
Ported 10.5 turbine housing
BR EVO9-5 turbo

Full 3" turbo back
No cat
Bullet muffler

Stock head, shortblock

1100 rpm 92.8 db's
4500 rpm 104 db's

[evoair]

Hi there Dave,

I thought I might clarify the human ears perceived response to loudness and the db scale. Loudness is measure of Phons and is very similar to the db scale at moderate listening levels. The db scale is a logarithmic scale, which means that you cant add/subtract as you normally would.

For every 10db increase there is a perceived doubling in loudness. This is the reason why sitting in a quiet room had @ 55db, but the exhausts @98db sounded well more than twice the volume.

"A" weighting the sound level meter, allows the meter to have a response similar to human hearing. "A" weighting basically reduces the sensitivity to high and low freq sounds, the same as the human ear does. Measuring using "C" weighting will give a db level higher than "A" as the freq response is flat.
If you are ever getting measured, please check that the meter is "A" weighted and on slow response.

There is normally an internal calibration signal button on the meter. This is used to adjust the needle on analog meters or zreo in didgtal meters.
Radio Shack sells quite a good analog meter, if anyone wants to buy one.

So please keep in mind this scale when viewing test results, as a 3db increase is a hell of alot in reality.

Thanks for making this forum a nice home for evo owners

Cheers
Aaron

[M_Acceleration]

This testing is baffling to me. So, I went into our lunch room and shut the door. The only thing in there is a large Pepsi machine and the fan on it was running. To me this is a VERY quiet room, very quiet. No other noises that I could detect. The decibels (DB's) in this room were 54 db's.

That will give you an idea. I don't fully understand this. If I hold my hand over the end of the meter at tight as I can it still reads around 53 db's. To me that should be 0 but maybe I am not grasping the concept.

David Buschur

yep a log scale

[travman]

wow the magnaflow is a lot quieter than the bullet.....Will we get to see magnaflow and bullet comparisons with high flow cats? Thats what will determine my final decision on which will be better for me in the area I live..

[David Buschur]

Remember the Magnaflow muffler test was through a STOCK cat and 2.5" downpipe. The stock cat is a BIG restriction and quiets the exhaust down a lot.

Aaron, thanks for the more indepth information on DB testing. I am using the "a" scale as Jarrod found that was for human ears somewhere. The meter has a calibration for 94 db's and I have calibrated it.

Thanks for the explanation.

David Buschur

[NEW2006EVOIX]

I'd like to see the differences between the three. I'm leaning more towards the 3" magnaflow since it seems like it's the quieter one with power. Also, what are the differences in power between the bullet and magnaflow?

Thanks.

[kmcconn9]

interesting to see that there isnt much difference between the 272's and revolvers in terms of db's...also the stage 3 head and block...

[NEW2006EVOIX]

Bump for updates

[David Buschur]

Very interesting stuff this morning.

I have a few cars. One of which is a 1987 Turbo Buick. On this car I was running the ATR single 3" exhaust. It was LOUD. Sounded good but loud. A couple years ago I moved the muffler from the rear where they had it to where the cat is suppose to go. To my surprise this quieted the car down quite a bit.

A year later I bought a beautiful 1995 Durango Copper, AWD Eagle Talon. It also had an ATR exhaust on it when I bought it. I also moved the muffler to where the cat was and again, was surprised at how much quieter the system got.

Next up was my brothers 1940 Ford Pick up. He runs a 4g63 in the truck and I put the muffler in the middle of the truck and built a tailpipe, it is 2.5" and is SO FREAKING quiet.

This brings me, finally, to my point. I just ordered a JDM EVO9 rear bumper cover for my RS. I was thinking about building the exhaust custom for this fascia so the muffler wasn't visable after the rear bumper cover swap. Then I got to thinking about all the above situations and the quieter exhausts.

Today I did fresh DB testing of my RS and dyno'd it. (poor freaking car) After this I pulled it off the dyno, installed a new bullet muffler where the cat usually goes, built a new section for the rear to replace the old muffler and repeated the testing.

Very odd finding. First thing I thought when I started the car was WOW it is A LOT quieter. My brother said the same thing. I then put it on the dyno and got the meter out.

Before at idle (1200 rpm on my car) was 91.5 DB's.
Before at 4500 rpm was 106.6 DB's.

After at idle was 92 DB's.
After at 4500 rpm was 107 DB's.

The meter moves around a bit from the pulsing of the exhaust but the point I am making is as much as it sounds quieter the meter says it is not.

Next oddity. Dyno. The low end (under 5,000 rpm) lost power and some boost. However after 5500 rpm or so the car gained power. The two comparisons made me very "confused" and unable to choose what I wanted to do, leave it like it is now or change back. I ended up choosing to leave it as the new rear bumper cover is going to look sweet with it like it is.

I then went for a road test. Took the decibel meter with me and held it up where my head is. At 55 mph in 5th gear, cruising, the car was at 82 db's inside with the windows up. Odd again, I rolled the window down and to me it sounded quieter in the car, I could barely hear the exhaust. Decibel meter told a different story, it went up to 86 db's.

These readings seem high so before anyone jumps the gun, my car has absolutely NO sound deadener in it what-so-ever, a very stiff suspension, solid motor mounts etc. The car is loud even if I shut it off and coast.

So this was suppose to be a huge break through but with the DB's outside the car and the power being a wash I am going to call it just another Buschur Racing test. Gained some a knowledge and maybe a car that is a little quieter on the inside.

David Buschur

[justchil]

I wonder if I could test my exhaust sound next time I come up? If it's not a huge deal to setup.. would be interesting to see.

[David Buschur]

Yes, I can test it. Isn't it our exhaust on your car?

David Buschur

[ERAAB]

Dave you can test my exhuast while my car is there if you want. Its a Turbo-XS.


ERIK RAAB

[brian 5150]

Very interesting stuff this morning.

I have a few cars. One of which is a 1987 Turbo Buick. On this car I was running the ATR single 3" exhaust. It was LOUD. Sounded good but loud.
David Buschur

and people think im jokeing when i say my talon is about a 100db at idle and its ungodly loud when its in the 4500 rpm range

[David Buschur]

As you can see, just tested Keith's EVO with dual bullet mufflers on it. One where the cat goes one in the rear.

90 db's at idle, 1200 rpm

103.4 db's at 4500 rpm

David Buschur

[David Buschur]

Have a great customer from the DC area. Been getting harrassed from his neighbors and police over his exhaust sound level. He has tried a few different exhausts. Came in yesterday with his BR built EVO with a full 3" exhaust with our bullet muffler on it. We took the bullet, cut it and installed it where the cat goes, then we installed a new Magnaflow muffler in the rear. UNFREAKING believable. This whole decibel testing has been baffling to me since I started it and this makes it worse.

The sound readings after this stuff was installed was very quiet.

1200 rpm (idle) was 88 db's.
4500 rpm was only 95 db's.

The car is quiet enough now that you can hear the engine over the exhaust standing behind the car. Inside the car, VERY quiet. It is surprising how just a few DB's less makes a huge difference to what you hear as loud.

David Buschur