How loud is your aftermarket exhaust? A call for decibels

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?

kannibul · 09-16-2009, 08:39 PM

Quote:

Originally Posted by kenchan

might want to include distance from the exhaust tip for out of car measurements...

Might want to come up with a standard of measurement...

IE, 3ft back, mic facing driver's side exhaust tip, centered.

Then maybe another sample from 10ft back, centered on the same plane between the tips.

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

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.

kdo2milger · 10-09-2009, 06:58 PM

reported TyiweonRaq as a dumba_ _

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?

onethreefive · 10-09-2009, 08:09 PM

Quote:

Originally Posted by kdo2milger

reported TyiweonRaq as a dumba_ _

Thanks for reporting. Took care of him.

kdo2milger · 10-09-2009, 10:22 PM

Quote:

Originally Posted by onethreefive

Thanks for reporting. Took care of him.

most excellent otf! glad to see you got AK's back

Minicobra1 · 10-09-2009, 10:45 PM

I heard someone on here got a noise ticket in Ca. they were running Stillen CBE & Berk HFC's. I'm curious to see how loud that combo is. I noticed that the test is suppose to be run at a constant RPM (see below) I wonder if this guy was accelerating when he got the ticket. Anyway, Here are the rules for California. Don't know how old this is.

CCR 1036 Passenger Cars and Light Trucks and Buses

Exhaust systems for motor vehicles, other than motorcycles, gross vehicle weight rating of less than 6,000 LB (2,722 kg) shall comply with the specified noise limits when tested in accordance with the following specifications:

(a) Measuring Site. The vehicle under test shall be positioned either on outdoor pavement or on a shop floor ( but not over a hoist or pit) in a location where the exhaust outlets are near an open shop door. No sound-reflecting surface other than the pavement and the vehicle being measured shall be within 10 ft (3.0m) of any part of the vehicle.

The testing is done in an environment in which there is minimal sound contamination. Please note that there is nothing stating highways or other public roads as being an exception to this criterion.

(b) Microphone Location. The microphone for the sound level meter shall be at the same height as the center of the exhaust outlet. The microphone shall be no closer to the pavement than 8 in. (203mm) when the exhaust outlet is lower than this height. The microphone shall be positioned with its longitudinal axis parallel to the ground, 20 inches plus or minus 1 inch (508mm plus or minus 24mm) from the nearest edge of the exhaust outlet, and 45 degrees plus or minus 10 degrees from the axis of the outlet. For exhaust outlets located under the vehicle body, the microphone shall be located at the specified angle and at least 8 in., (203mm) from the nearest part of the vehicle. For exhaust outlets that make an angle of 45 degree or less with the longitudinal axis of the vehicle, the microphone shall be outboard of the exhaust axis. For exhaust outlet angles of more than 45 degrees, the microphone shall be on the side of the exhaust axis to the rear of the vehicle.

This denotes where the sound measuring device is relatively close to the exhaust outlet. Notice that it does not make any references to provisions for sound level testing done from distances greater than 21 inches. <

(c) Engine Operation. The engine shall be at a normal running temperature with the transmission in neutral. System sound level measurements conducted for certification by exhaust manufacturers shall be made at an average steady-state engine speed of three-quarters of maximum rpm. Sound level measurements conducted by licensed muffler certification stations shall be made at an average steady-state engine speed of 3,000 rpm for vehicles manufactured before 1972 for which the station does not have a maximum rpm data.

Please notice that the engine is supposed to be running and the law has no provisions for parked vehicles. Note that the certification can be done by the manufacturer of the exhaust system. There is no requirement that the manufacturer sound test each individual vehicle. Re: "licensed muffler certification stations," the letter from the California Highway Patrol file Number 60.A9190.A9181.062.9610186 states in the third paragraph that these facilities were canceled in 1978 due to budgetary cut-backs.

(d) Exhaust Sound Level Measurement. The recorded exhaust system sound level of a stationary vehicle shall be the highest reading obtained during the test, disregarding unrelated peaks due to extraneous ambient noise. When there is more than one exhaust outlet, the reported sound level shall be for the loudest outlet. When there are two or more exhaust outlets separated by less than 12 in. (305mm), measurements shall be made on the outlet closest to the side or rear of the vehicle. (Figure 4). The sound level for the motor vehicles with the manufacturers' gross vehicle ratings of less than 6,000 LB (2,722 kg) except motorcycles, shall not exceed the following limit:

The statement stating extraneous ambient noise refers to noise coming from places other than the exhaust. For this reason, testing cannot be done in a sound-contaminated environment. It would be logical that a roadside or a highway would be a sound-contaminated environment.

(1) Sound Level Limit. The exhaust noise shall not exceed 95 dB(A).

kdo2milger · 10-09-2009, 10:48 PM

is that 95db at idle rpm?

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)

09-16-2009, 10:01 PM	#19 (permalink)
Nikon FM Track Member Join Date: Jan 2009 Location: Snoqualmie WA Posts: 973 Drives: 03 996TT Porsche Rep Power: 606	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, 10:45 PM	#27 (permalink)
Minicobra1 A True Z Fanatic Join Date: Nov 2008 Location: Orange County, CA. Posts: 1,205 Drives: 370Z Tour, Spt, 6mt Rep Power: 644	I heard someone on here got a noise ticket in Ca. they were running Stillen CBE & Berk HFC's. I'm curious to see how loud that combo is. I noticed that the test is suppose to be run at a constant RPM (see below) I wonder if this guy was accelerating when he got the ticket. Anyway, Here are the rules for California. Don't know how old this is. CCR 1036 Passenger Cars and Light Trucks and Buses Exhaust systems for motor vehicles, other than motorcycles, gross vehicle weight rating of less than 6,000 LB (2,722 kg) shall comply with the specified noise limits when tested in accordance with the following specifications: (a) Measuring Site. The vehicle under test shall be positioned either on outdoor pavement or on a shop floor ( but not over a hoist or pit) in a location where the exhaust outlets are near an open shop door. No sound-reflecting surface other than the pavement and the vehicle being measured shall be within 10 ft (3.0m) of any part of the vehicle. The testing is done in an environment in which there is minimal sound contamination. Please note that there is nothing stating highways or other public roads as being an exception to this criterion. (b) Microphone Location. The microphone for the sound level meter shall be at the same height as the center of the exhaust outlet. The microphone shall be no closer to the pavement than 8 in. (203mm) when the exhaust outlet is lower than this height. The microphone shall be positioned with its longitudinal axis parallel to the ground, 20 inches plus or minus 1 inch (508mm plus or minus 24mm) from the nearest edge of the exhaust outlet, and 45 degrees plus or minus 10 degrees from the axis of the outlet. For exhaust outlets located under the vehicle body, the microphone shall be located at the specified angle and at least 8 in., (203mm) from the nearest part of the vehicle. For exhaust outlets that make an angle of 45 degree or less with the longitudinal axis of the vehicle, the microphone shall be outboard of the exhaust axis. For exhaust outlet angles of more than 45 degrees, the microphone shall be on the side of the exhaust axis to the rear of the vehicle. This denotes where the sound measuring device is relatively close to the exhaust outlet. Notice that it does not make any references to provisions for sound level testing done from distances greater than 21 inches. < (c) Engine Operation. The engine shall be at a normal running temperature with the transmission in neutral. System sound level measurements conducted for certification by exhaust manufacturers shall be made at an average steady-state engine speed of three-quarters of maximum rpm. Sound level measurements conducted by licensed muffler certification stations shall be made at an average steady-state engine speed of 3,000 rpm for vehicles manufactured before 1972 for which the station does not have a maximum rpm data. Please notice that the engine is supposed to be running and the law has no provisions for parked vehicles. Note that the certification can be done by the manufacturer of the exhaust system. There is no requirement that the manufacturer sound test each individual vehicle. Re: "licensed muffler certification stations," the letter from the California Highway Patrol file Number 60.A9190.A9181.062.9610186 states in the third paragraph that these facilities were canceled in 1978 due to budgetary cut-backs. (d) Exhaust Sound Level Measurement. The recorded exhaust system sound level of a stationary vehicle shall be the highest reading obtained during the test, disregarding unrelated peaks due to extraneous ambient noise. When there is more than one exhaust outlet, the reported sound level shall be for the loudest outlet. When there are two or more exhaust outlets separated by less than 12 in. (305mm), measurements shall be made on the outlet closest to the side or rear of the vehicle. (Figure 4). The sound level for the motor vehicles with the manufacturers' gross vehicle ratings of less than 6,000 LB (2,722 kg) except motorcycles, shall not exceed the following limit: The statement stating extraneous ambient noise refers to noise coming from places other than the exhaust. For this reason, testing cannot be done in a sound-contaminated environment. It would be logical that a roadside or a highway would be a sound-contaminated environment. (1) Sound Level Limit. The exhaust noise shall not exceed 95 dB(A). __________________ 370z Tour\| Spt Pack\|Navi\|BERK CBE\|Berk HFC's\| Eibach Springs\| Hotchkis Sway Bars\|SPC Camber Arms\|15mm Ichiba Wheel Spacers\| 19"Factory Nismo Wheels-Matt Black\|Stop Tech Rotors\|TWM Shifter\|3M Tint\|Black Fangs\|Black Rear Valance\|JDM Fog Light\| MY BAND-www.myspace.com/petroleum Last edited by Minicobra1; 10-09-2009 at 10:49 PM.

10-09-2009, 10:48 PM	#28 (permalink)
kdo2milger OG Priesthood Join Date: Feb 2009 Location: Fargo, ND Posts: 17,859 Drives: NISMO T Rep Power: 59	is that 95db at idle rpm? __________________ Project *NISMO*

10-09-2009, 11:21 PM	#29 (permalink)
jpit Enthusiast Member Join Date: Feb 2009 Location: Washington State Posts: 440 Drives: 370Z Tour MT w/Spt Rep Power: 16	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.

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09-16-2009, 08:42 PM	#18 (permalink)
kannibul A True Z Fanatic Join Date: Jun 2009 Location: Jenks, OK Posts: 2,281 Drives: 370z Touring/Sport Rep Power: 266	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	#20 (permalink)
spearfish25 A True Z Fanatic Join Date: Mar 2009 Location: Naples, FL Posts: 4,117 Drives: to work Rep Power: 1856	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	#24 (permalink)
spearfish25 A True Z Fanatic Join Date: Mar 2009 Location: Naples, FL Posts: 4,117 Drives: to work Rep Power: 1856	Of all the threads to choose too. Maybe he missed the Fast Intentions thread with nearly 3,000 posts?