Decibel Meters, anyone use them?

[BavarianZHP]

Sound... There's a tool that humans have invented that can quantitatively measure its amplitude, yet I hear nothing about it. Are they just not very reliable? Are they just not precise enough since it's on a log scale?

I'm by no stretch a sound engineer, but I have always thought it would be a great idea to place a decibel label to different exhausts, headers/mods, intake noise, tire/road noise, cabin noise, sound systems, you name it. Something that I can label and compare directly, rather than through vague comparisons... I read and hear too often of "oh, the noise is slightly louder than <so and so>" or "this cabin seems more quiet <than another>". Needless to say, it doesn't help me much. :dunno

Maybe I'm just a geek, but if we provided each other frequency vs amplitude graphs, that would make my day. (Of course things would be compared in like/controlled sound environments)

Now for those that have used decibel/sound meters, how do you use them? Most I have seen (on tv lol) just have a single digital readout (one channel system?) that I assume picks up the highest amplitude within the audible frequency band? Does it also tell you which frequency it is measuring? Are there multichannel systems that pick up the amplitude of multiple frequencies (eg: high freq = X decibels, low freq = Y decibels, mid freq = Z decibels?)? It just surprises me why no one ever quantitatively talks about sound... This would resolve so many discussions!

I'm really interested in how my ZHP cabin noise is affected when I will inevitably switch tires (and also would like to compare it to my bro's e39), or how adding sound deadening, changing exhaust... affect the sound - stuff like that. I want to be able to quantitatively measure the difference. Any thoughts? I've been eyeing tools on amazon/ebay.

[M0nk3y]

Only dB I've dealt with is with SCCA Autocross.

You can't bust 98 dB at 50 feet during a full throttle part of the course. They usually have a station set up on this area

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[Stewbie]

Same for our autocross club, except we only get 92db at 50ft, and our events are held at an airport! :)

[derbo]

Sound... There's a tool that humans have invented that can quantitatively measure its amplitude, yet I hear nothing about it. Are they just not very reliable? Are they just not precise enough since it's on a log scale?

I'm by no stretch a sound engineer, but I have always thought it would be a great idea to place a decibel label to different exhausts, headers/mods, intake noise, tire/road noise, cabin noise, sound systems, you name it. Something that I can label and compare directly, rather than through vague comparisons... I read and hear too often of "oh, the noise is slightly louder than <so and so>" or "this cabin seems more quiet <than another>". Needless to say, it doesn't help me much. :dunno

Maybe I'm just a geek, but if we provided each other frequency vs amplitude graphs, that would make my day. (Of course things would be compared in like/controlled sound environments)

Now for those that have used decibel/sound meters, how do you use them? Most I have seen (on tv lol) just have a single digital readout (one channel system?) that I assume picks up the highest amplitude within the audible frequency band? Does it also tell you which frequency it is measuring? Are there multichannel systems that pick up the amplitude of multiple frequencies (eg: high freq = X decibels, low freq = Y decibels, mid freq = Z decibels?)? It just surprises me why no one ever quantitatively talks about sound... This would resolve so many discussions!

I'm really interested in how my ZHP cabin noise is affected when I will inevitably switch tires (and also would like to compare it to my bro's e39), or how adding sound deadening, changing exhaust... affect the sound - stuff like that. I want to be able to quantitatively measure the difference. Any thoughts? I've been eyeing tools on amazon/ebay.


dB is a measure of intensity. It measures amplitude. it is independent of frequency. A high pitch noise that is loud can have the same dB reading as a low frequency noise of equal loudness.

It only can measure relative sound intensity. If you do use a decibel meter, you will need to have a static location for the device to keep the tests consistent. Ie suction to the inside of the sunroof or window. The road material and condition will also be a variable that would need to be eliminate with the same course during the experiments. A static location like a soundbooth at the track is good one to eliminate the variables from inside.

There is alot of variables to take into account and you should eliminate as many unknowns to make sure whatever variable you are trying to analyze is truly the reason for the changes in the experiment. Hope this helps!

[billyjack]

I use a decibel meter all the time but never to measure my car :). I use them to calibrate the studios I work in. As derbo mentioned they strictly measure amplitude. You'd need something like a Real Time Analyzer to measure frequency as well and plot it into a graph. Then you could differentiate between a low exhaust note and a high whiny one. Decibel meters and measurement microphones are extremely sensitive and need to be mounted on static shock resistant mounts to measure accurately. But the harder part would be eliminating variables of the environment which help shape the way cars (and everything else) sound to us.

Its a great idea but I don't know how you'd get reliable and consistent results.

[az3579]

I had to get my car measured when I put my TSE3 exhaust on. The limits I have to adhere to is I believe now it's 89dB. I forget Lime Rock's policy since that damn limit seems to get lower every year. Sheesh.

With a stock intake the TSE measured at 89dB at 50 feet. I think Lime Rock takes measurements at 75 feet so I think I'm good... haven't gotten black flagged for it yet!

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[damonchoy]

Stock intake and UUC TSE is 89dB at 50 feet?

Wonder what mine would be like with catless headers, Carbonio intake and Rogue DMS at 50 feet, then!

Also, if I recall correctly NASIOC (North American Subaru Impreza Owner's Club) used to have a master list of almost every exhaust with decibel readings included. It was really neat and I think it's a great idea.

[az3579]

Stock intake and UUC TSE is 89dB at 50 feet?

Wonder what mine would be like with catless headers, Carbonio intake and Rogue DMS at 50 feet, then!

Also, if I recall correctly NASIOC (North American Subaru Impreza Owner's Club) used to have a master list of almost every exhaust with decibel readings included. It was really neat and I think it's a great idea.

Keep in mind that 50 feet isn't the standard distance to measure sound. I think most places measure at 75 feet or longer. That extra 25 feet makes a huge difference.

Of course now, I have a GruppeM intake with the TS3 (stock headers) so that definitely gives it more growl. I wonder if it'll show up on the sound meter are being significantly more... it certainly is louder.

[derbo]

http://cdn.nexternal.com/uuc/images/SAEJ1169_TSE3.gif

TSE3 test with california sound laws.

[M0nk3y]

Does anyone else find that to be a very stupid standard?

Exhaust with no engine load is COMPLETELY different than an exhaust under load

[az3579]

http://cdn.nexternal.com/uuc/images/SAEJ1169_TSE3.gif

TSE3 test with california sound laws.

What distance is that taken at though?

[RITmusic2k]

FYI, since we're not tuning room acoustics here, you don't need the most precise equipment to satisfy your own curiosity...

If you have a smartphone you can probably choose from a multitude of decibel meter apps to download.

For my iPhone, I have an app from a company called Performance Audio called 'Audio Tool', which has all sorts of features, but they offer a stripped down standalone app called dB Meter Pro (and a free version called dB Meter). They're quite good at giving you a relatively accurate picture of how loud your particular system is.