iPhone Sound Meter App

Hooper · March 16, 2013, 01:44:56 AM

Playing with my 1377 carbine and 2400KT trying to get accurate sound measurements. Had in mind long and short barrels, number of pumps, etc. Hard to tell by ear what's louder than what. Downloaded an iPhone app called Decibel 10th. Looked pretty good and didn't cost a thing; nothin' to lose.

But after running a string of shots I had readings that ran from High 70's to low 90's. Discounting the outliers I still had a range of 10db. Even if the absolute numbers weren't correct I would have been happy with a fairly narrow consistent range. But 10db would indicate that some shots were 10 times louder than others with nothing changed. Doesn't seem right.

There are a bunch of similar apps. Anyone have luck with any of them?

arkmaker † · March 16, 2013, 01:48:32 AM

Did you follow directions for calibrating the app? I had some weird readings until I made sure everything was set up right in the software and distance to muzzle maintained.
Rich

quickster47 † · March 16, 2013, 01:54:24 AM

Quote from: arkmaker on March 16, 2013, 01:48:32 AM
Did you follow directions for calibrating the app? I had some weird readings until I made sure everything was set up right in the software and distance to muzzle maintained.
Rich

What Rich pointed out is very, very true. A good and proper calibration makes all the difference in the world to these phone apps for measuring sound levels.

Carl

breakfastchef · March 16, 2013, 02:52:32 AM

I've had good luck with dB Meter Pro for the iPhone. SPL readings seem to be pretty consistent. I prefer to take readings outdoors because pellet impacts on a target can sometimes be louder than some guns and throw off your measurements. As long as the app is fairly accurate, you can establish a reasonable scale of loudness for your guns. A 10dB spread is too wide a variance.

Hooper · March 16, 2013, 05:38:39 AM

Thanks for the quick responses. There is a calibration slider in the app but no directions as to how to use it. Checked in the app, iTunes and developer website. I can adjust the sample update frequency up to 10 Hz which I did hoping that would give a good sample.

Breakfastchef dB Meter Pro is no longer available but there is another app called Decibel Meter Pro that is highly rated. Will give it a shot for .99 cents.

arkmaker † · March 16, 2013, 02:14:02 PM

I am using a Kindle Fire HD and got a couple of the free sound apps. The calibration is crude, but I went by what we get in the shop around our cnc lathes. We are always being monitored for sound levels by the safety/environmental group, so I had a solid base to adjust mine to.
I think that the muzzle placement will make a big difference in your readings.
Does your program record the readings? Mine does not. I wish it did, so I could compare one ldc to another.

Hooper · March 16, 2013, 03:34:55 PM

arkmaker

The first app that I used, Decibel 10th, records readings and will send the results to your email. I tried it and I got a zipped .csv file that I was able to open with Excel. I think it recorded a reading every tenth of a second or so which gave me a very long list, not just peak readings. I was going to use an excel formula that eliminated all readings below 70dB for example. Didn't bother to follow up since the peak readings were all over the place. Possibly adjusting the app settings and relocating the phone a bit further away from the muzzle will help. I'll try it and see. Might have had the phone too close to the muzzle blast to get accurate readings.

I've also installed Decibel Meter Pro and will try that too. I'll post something when I get done.

7624452 · March 16, 2013, 09:24:32 PM

I'm currently allergic to anything made by apple, but I have a nice Android app.
https://play.google.com/store/apps/details?id=kr.sira.sound&hl=en

7624452 · March 16, 2013, 09:30:24 PM

[youtube]https://www.youtube.com/watch?v=gBhVOH5fxE8#ws]Sound Meter Apps for Android and iPhone App Reviews[/url]

Hooper · March 17, 2013, 01:28:11 AM

Hi Art,

Thanks for your postings. I actually like Android. I had an original Motorola Droid early on and stuck with it right up until my Samsung Galaxy Nexus. Just got worn out by the Android chaos. Gingerbread, Ice Cream etc., apps that didn't work, and lack of integration between apps and OS. Only switched with the iPhone 5 introduction. Very bland but most everything works. (And I already had a MacBook Pro).

Back to the sound meter stuff. There are just so many "sound meter" apps it's hard to decide where to begin. I'm going to work with some stuff and see if I can find something that works for me. First app I tried (Decibel10th) seems very sensitive and picks up small sound differences. Problem is that it has difficulty responding to rapid level increases. More or less "dead quite" to the "pow" of the 2400KT. Those big spikes in sound level don't seem to get recorded properly. With the phone about 3 feet to the side of the muzzle I got readings that varied from 73dB to 94db. Thats a 20dB difference which means the loudest shot was 1000 times louder than the quietest. No way. Phone might be too close so I'll make a few more test runs.

7624452 · March 17, 2013, 02:03:08 AM

I believe the accuracy probably depends on the quality of the microphone that is built into your telephone. Is it possible to attach an external mike to a phone ?

Hooper · March 17, 2013, 05:18:00 PM

An external mic might help and fortunately the iPhone has a 3.5mm input for a microphone. I have a decent quality Sony mic around somewhere so I'll take a look for that. Will undoubtedly need an adaptor of some sort.

In the meantime I have had some success with dBMeter Pro by Performance Audio. I mention that because it's hard to differentiate one app from another with the very similar names.

It's giving me fairly consistant readings and has dB A, B, and C filters. C filter is said to be useful for recording high sound pressure levels according to the literature. So far I'm getting readings plus/minus 2 dB but the absolute value seems too high at around 104 dB. Probably needs some calibration. At least it looks like I'll be able to get numbers that will allow me to compare one setup with another. More testing needed.

breakfastchef · March 17, 2013, 09:00:17 PM

Quote from: Hooper on March 17, 2013, 05:18:00 PM
So far I'm getting readings plus/minus 2 dB but the absolute value seems too high at around 104 dB. Probably needs some calibration. At least it looks like I'll be able to get numbers that will allow me to compare one setup with another. More testing needed.

Do not worry so much about the absolute value when employing this tool. It is not meant to replace a $2,000 SPL meter. Rather, if it remains fairly consistant, compare the relative differences between your guns. Think of it as producing comparative, not absolute, readings.

Hooper · March 17, 2013, 10:39:28 PM

Right, it's the comparison that matters not the actual number. I don't have anything to calibrate against anyway.

Been trying various combinations and I think I've got it pretty much worked out. Using a 1377 (PC77) I get very consistent readings like plus or minus 1dB after making an adjustment to the app parameters and moving the phone further away from the muzzle blast. Adjusted the sensitivity down from 0.10s to 0.05s. Not clear what the units of measure are, or what it does, but it gives more consistent numbers. An interesting observation is that it is accurate enough to detect the difference between 10 vigorous pumps and 10 lazy pumps. Readings of 108dB down to 104-105dB if that makes sense.