I was thinking about how loud my pipes are and if the new set up I get is going to be as loud, louder, or quieter. So I came up with an idea. Let's have a decibel thread. Every app store has a free sound meter app. Download the app run it put your bike outside and record the decibels from your seat at idle 2000rpm, 3000rpm, and 4000rpm. Then post what the results were and what your set up is and maybe how old the pipes are as this seems to affect the decibels. I would go first but I am at work so I will post the results later.
This could also work with radios.

 

I like your enthusiasm, however there are too many variables involved. You need to set a distance from the pipes so there is a standard. I think every phone or device will read differently do to microphone placement and component differences. Also I'm sure there are several different apps and you will probably get different readings with each different app.

I'm an electrician, we sometimes have to use a light meter to read foot candles of light. Every light meter app I tried gave different results. None of them actually matched what our true light meter read.

Set a couple standards and try a few apps. Then suggest an app so everyone is on the same page. Good luck with the experiment.

 

This is exactly the same reason those YouTube clips of exhaust systems are not very useful in picking out your new pipes.
They very rarely sound anything like they did on the video clip once you get them installed on your bike, and listen to them with your own ears.

 

I tried three sound meter apps on my.phone, they were all within 1or2 decibels of each other.
In was thinking simply sit on your bike with it standing up with the phone about chest high, flat so you can read it.
It won't be scientific but it will give a general idea.

 

the standard is sound meter at 45º angle from the pipe outlet, 1 meter away, 12" above the pavement.

phone and apps encompass too many variables, each type of microphone and processor will have compression and expansion differing frequency response
...checking my own last 3 iphones and various apps against a professional quality dB meter, shows that the phone apps are no better than a guess.
In one extreme case 1 app was about 6dB high at 80 dB, about right at 96 dB and again way high over 105 dB

if YOU use you same method and equipment to measure then you'll have a comparison for various pipes, but that may not transfer to other users and their phones.
You may find that the compression circuit in your phone/processor doesn;t allow the dynamic range needed

Mike

 

Huh?.....What?....You say something'? Yup, those pipes sound loud to me!

 

1.2 dB is still significant. CDC tested a bunch of phone apps and found only (about) 10 of them to be acceptable.

 

Part of my job is making SPL measurements (dB sound checks) to make sure we are in compliance with the city's rules and regulations. I use a very expensive Bruel & Kjaer sound pressure meter, I once had a police officer aproach me and ask if he could compare his iphone's app to my meter. His readings were off by 6dB high in some cases, depending on audio frequency. I explained to him that a cell phone's mic is designed for a very narrow audio bandwidth and within that it also has audio peaks and dips purposely designed in to accentuate voice communication. A sound pressure level meter's microphone has a very broad and flat frequency response. This is done to faithfully and accurately capture all sonic ranges, unfortunately cellphone mic are nowhere near accurate to make calibrated sound tests.

 

Being deaf, Ive always felt that I should have the loudest bike....I cant hear you coming, so Im gonna make damn sure you hear me... that being said, I cant tell how LOUD my pipes are through normal means, i just go off of what shakes off the shelves and walls in the garage while its running... my FXRs over-unders are really loud, and sound good. I get comments all the time on how good it sounds. My FLHX is much deeper but loud as well... between the two I prefer the bigger bikes pipes... you can feel that rumble down to your toes from 20 feet away and its earth shaking without being ear-splitting painful once it gets going.

 

What are your thoughts on a radio shack meter vs a cell phone app? I read about the tests CDC did and picked one of the few apps they liked - its called SPLnFFT. The RS meter has two weighting choices, A of C - on the cell phone it has several weighting choices - dB, dB(A), dB(B) and dB(C) I have no idea which one to use and got no answers from the app designer. Any idea?