How loud is your aftermarket exhaust? A call for decibels

kdo2milger · 09-16-2009, 07:55 PM

Quote:

Originally Posted by JB1

Hey spearfish,

I don't have a decibel meter, but I did just get Berk HFC's installed. I'm in the Chicago burbs and would not mind driving by down town if you want to get a reading on the loudness of those.

I'm in, any kind of beer in particular?

nope, just your usual

spearfish25 · 09-16-2009, 08:17 PM

Cool, I'm down with that. You have the Berk HFCs and otherwise stock exhaust?

I sent you a PM.

Quote:

Originally Posted by JB1

Hey spearfish,

I don't have a decibel meter, but I did just get Berk HFC's installed. I'm in the Chicago burbs and would not mind driving by down town if you want to get a reading on the loudness of those.

I'm in, any kind of beer in particular?

JB1 · 09-16-2009, 11:14 PM

Quote:

Originally Posted by spearfish25

Cool, I'm down with that. You have the Berk HFCs and otherwise stock exhaust?

I sent you a PM.

Got the PM, thanks.

Yep, I have the Berk HFC's with a stock exhaust. I'm actually surprised at how much louder this already is compared to the stock cats. I'm now trying to decide whether I want to stick with this or go for an aftermarket exhaust as well. The sound now is ok, but a bit harsh, wouldn't mind a somewhat "deeper" sound.

kannibul · 09-16-2009, 08:42 PM

I live out in the middle of a social desert (compared to most of you east/west coasters), but there are those flat rate USPS boxes that aren't too bad for shipping anywhere...

We could ship around mine (it's sitting in a closet doing nothing) and get readings from everyone off the same meter.

Nikon FM · 09-16-2009, 10:01 PM

These are either dB"A" or dB"C" meters. The difference in A or C weighting is that the noise is measured and adjusted on a third octave band basis by either an A-weighted curve or C-weighted curve, essentially different values for each third octave band frequency. After the A or C adjustment a log sum of the frequency range (specified on each meter specs) is performed. The number that is shown on the display will be the log sum value.

If someone has a dBA meter and another person has a dBC meter the answers will be different from the same noise source, in addition some meters have different frequency ranges the adjustments are performed on so another different answer.....

The dBA or dBC weighting were established as a means to measure noise environments as the ear hears them and to determine hearing damage due to exposure.

Too much blah blah blah acoustics but if people start comparing numbers knowing the background information A or C weighted and frequency range determined over would be helpful.

What's really cool (at least for an acoustics guy) but expensive, would be a third octave band analyzer.

Real Time Analyzer and Sound Level Meter with 1/3 Octave Band Filters

spearfish25 · 09-16-2009, 10:07 PM

I updated the original post to request A weighted values. Some meters like mine from radioshack give the option of either weighting. My understanding is that c is best for music and includes a wider frequency range that is beyond our audible range. A weighting stops at a low frequency of 500hz, and a site I saw suggested it's best for car sound readings. As an aside, my values are listed as A weighted. When I used c weighted, everything was about 10db louder.

Nikon FM · 09-16-2009, 10:14 PM

Quote:

Originally Posted by spearfish25

I updated the original post to request A weighted values. Some meters like mine from radioshack give the option of either weighting. My understanding is that c is best for music and includes a wider frequency range that is beyond our audible range. A weighting stops at a low frequency of 500hz, and a site I saw suggested it's best for car sound readings. As an aside, my values are listed as A weighted. When I used c weighted, everything was about 10db louder.

Exhaust sounds will have quite a bit of energy below 500Hz.

For perspective...the base beat that goes through you from someone's seriously amped car audio is typically 20Hz-40Hz

spearfish25 · 10-09-2009, 07:14 PM

Of all the threads to choose too. Maybe he missed the Fast Intentions thread with nearly 3,000 posts?

jpit · 10-09-2009, 11:21 PM

On the 370Z it would be about a steady state 5600 rpm. I don't think our stock exhaust would pass that.

Minicobra1 · 10-09-2009, 11:42 PM

Quote:

Originally Posted by jpit

On the 370Z it would be about a steady state 5600 rpm. I don't think our stock exhaust would pass that.

Yeah, should pass no problem, it's only under load or revving that this engine get loud, steady rpm should be fine.

Look at OP, his DB rating is without mufflers. (although not following mic placement guidelines) gives us some kind of idea.

Stock Muffler Delete, replaced with custom bent aluminum tubes to tips.
~75-80db idle in car while warm
~80-85db in car while in 6th gear on highway (around 70-80mph)
~96db out of car under heavy acceleration
~104db inside car under heavy acceleration in 4k-5k rpm range (drone zone)

spearfish25 · 10-10-2009, 06:33 AM

Umm, yeah. Despite my readings being from a muffler delete, I think we would fail miserably. The microphone has to be 20 INCHES from the exhaust outlet. That 96dB was from about 300 feet away (watch the video again). It's probably 130dB at the tips (all I know is I did't want my ears anywhere near that close when I had the muffler off). Even with just the Stillen CBE now, I think I'd still fail to meet those guidelines.

Hell, I bet engine noise alone (forget the exhaust) would be over 95dB at 20 inches from the tips.

370Zsteve · 10-10-2009, 06:47 AM

Great thread! Look forward to some results.............................

spearfish25 · 10-11-2009, 12:12 AM

Quote:

Originally Posted by 370Zsteve

Great thread! Look forward to some results.............................

Stock cats with Stillen CBE to be added shortly...

choonga · 01-28-2010, 07:13 PM

any updates?

spearfish25 · 01-28-2010, 10:08 PM

Stillen CBE with ERZ High Flow Cats. 89dB at WOT inside the car

09-16-2009, 10:01 PM	#5 (permalink)
Nikon FM Track Member Join Date: Jan 2009 Location: Snoqualmie WA Posts: 973 Drives: 03 996TT Porsche Rep Power: 607	A little calibration (no pun intended) These are either dB"A" or dB"C" meters. The difference in A or C weighting is that the noise is measured and adjusted on a third octave band basis by either an A-weighted curve or C-weighted curve, essentially different values for each third octave band frequency. After the A or C adjustment a log sum of the frequency range (specified on each meter specs) is performed. The number that is shown on the display will be the log sum value. If someone has a dBA meter and another person has a dBC meter the answers will be different from the same noise source, in addition some meters have different frequency ranges the adjustments are performed on so another different answer..... The dBA or dBC weighting were established as a means to measure noise environments as the ear hears them and to determine hearing damage due to exposure. Too much blah blah blah acoustics but if people start comparing numbers knowing the background information A or C weighted and frequency range determined over would be helpful. What's really cool (at least for an acoustics guy) but expensive, would be a third octave band analyzer. Real Time Analyzer and Sound Level Meter with 1/3 Octave Band Filters __________________ Buddy Revell: "One man's sooner is another man's later"

10-09-2009, 11:21 PM	#9 (permalink)
jpit Enthusiast Member Join Date: Feb 2009 Location: Washington State Posts: 440 Drives: 370Z Tour MT w/Spt Rep Power: 17	On the 370Z it would be about a steady state 5600 rpm. I don't think our stock exhaust would pass that. Last edited by jpit; 10-09-2009 at 11:26 PM.

10-10-2009, 06:33 AM	#11 (permalink)
spearfish25 A True Z Fanatic Join Date: Mar 2009 Location: Naples, FL Posts: 4,117 Drives: to work Rep Power: 1857	Umm, yeah. Despite my readings being from a muffler delete, I think we would fail miserably. The microphone has to be 20 INCHES from the exhaust outlet. That 96dB was from about 300 feet away (watch the video again). It's probably 130dB at the tips (all I know is I did't want my ears anywhere near that close when I had the muffler off). Even with just the Stillen CBE now, I think I'd still fail to meet those guidelines. Hell, I bet engine noise alone (forget the exhaust) would be over 95dB at 20 inches from the tips. Last edited by spearfish25; 10-10-2009 at 06:39 AM.

10-10-2009, 06:47 AM	#12 (permalink)
370Zsteve A True Z Fanatic Join Date: Sep 2009 Location: Gold Coast CT Posts: 10,599 Drives: 2019 Corvette G.S. Rep Power: 43	dB Great thread! Look forward to some results.............................

01-28-2010, 10:08 PM	#15 (permalink)
spearfish25 A True Z Fanatic Join Date: Mar 2009 Location: Naples, FL Posts: 4,117 Drives: to work Rep Power: 1857	Stillen CBE with ERZ High Flow Cats. 89dB at WOT inside the car __________________ 2013 Cadillac V-Wagon, RIP Z

09-16-2009, 08:42 PM	#4 (permalink)
kannibul A True Z Fanatic Join Date: Jun 2009 Location: Jenks, OK Posts: 2,281 Drives: 370z Touring/Sport Rep Power: 267	I live out in the middle of a social desert (compared to most of you east/west coasters), but there are those flat rate USPS boxes that aren't too bad for shipping anywhere... We could ship around mine (it's sitting in a closet doing nothing) and get readings from everyone off the same meter.

09-16-2009, 10:07 PM	#6 (permalink)
spearfish25 A True Z Fanatic Join Date: Mar 2009 Location: Naples, FL Posts: 4,117 Drives: to work Rep Power: 1857	I updated the original post to request A weighted values. Some meters like mine from radioshack give the option of either weighting. My understanding is that c is best for music and includes a wider frequency range that is beyond our audible range. A weighting stops at a low frequency of 500hz, and a site I saw suggested it's best for car sound readings. As an aside, my values are listed as A weighted. When I used c weighted, everything was about 10db louder.

10-09-2009, 07:14 PM	#8 (permalink)
spearfish25 A True Z Fanatic Join Date: Mar 2009 Location: Naples, FL Posts: 4,117 Drives: to work Rep Power: 1857	Of all the threads to choose too. Maybe he missed the Fast Intentions thread with nearly 3,000 posts?

01-28-2010, 07:13 PM	#14 (permalink)
choonga Base Member Join Date: Aug 2009 Location: Melbourne, Australia Posts: 51 Drives: Red 09 370z 6MT Rep Power: 16	any updates?

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