I thought it would be useful to create a thread for BT that would keep track of sound levels for a wide rage of aircraft. Here is an iPhone app you can download for free so that anyone posting here can use the same tool for consensus.

It would also be great if anyone doing an interior with soundproofing could post before and after. Might save us some money or really help the interior shops sell some additional product!

In my FAA Makeover thread, I posted before and after interior sound tests with a professional meter. Before interior it was 94db, after 91.5. My buddies 72 Vtail is 92.5 with nothing special done. a 76 F33A time capsule I was flying for awhile was also 92.5. With noise cancelling headsets, I couldn't tell a differeence.

I was waned here on BT that sound deadning wouldn't make a difference, and they were right, it doesn't and is a waste of money.

Great idea James, I will download that app and report back.

Unless you use calibrated sound meters, the results won't mean much. There is just far too much variation from unit to unit, device type to type, and from app to app to make the numbers comparable.

Mike C.

Unless you use calibrated sound meters, the results won't mean much. There is just far too much variation from unit to unit, device type to type, and from app to app to make the numbers comparable.

Mike C.

I have that app on my phone and was playing with it in the airplane (71V35B) and found it a little dependent on what my cruise settings were. I think (cant remember exactly) I was registering around 90-91 at 1450RPM. Thought that was really loud so turned it off and went back into denial that my plane was a quiet one.

I was going to re-check it after installing a new door seal and fire wall access seal.

Depending on the accuracy of the meter you did gain some reduction. A 2.5db noise reduction doesn't sound like a lot, but remember that a 3 db reduction is 50% of the sound pressure level and about an 18% reduction in perceived volume.

no, they are useless. We all pull out our phones and play with these apps while we are doing vehicle sound testing with real instrumentation. Phone-phone variability in the same spot with the same app, is huge. They are a joke.

no, they are useless. We all pull out our phones and play with these apps while we are doing vehicle sound testing with real instrumentation. Phone-phone variability in the same spot with the same app, is huge. They are a joke.

This is a well known fact.

Most cell phones use noise canceling microphones, either a single mic element with dual ports or dual mics that cancel each other out. Wrong tool for measuring background noise.

I have that app on one phone (iPhone) and a similar app on another (Android). There is about a 20-25dB difference between the two with them just sitting on my desk. A bit over 50dB "quiet street" vs a bit under 30dB "rustling leaves." I'll pick the lower number and go with that.

I downloaded that exact app a while back for the same purpose. While I don't think it's very useful to compare different aircraft for the reasons already mentioned, I do think it has some value. I was interested to know where my noise was coming from. I moved the phone all around the plane to find the "leaks".

It somewhat agreed with common sense which suggested that more mass = better sound reduction. Phone up against the panel might be @90 decibels and below panel (shin height) might be 94 decibels. Up near windscreen also 94 decibels. So the point here was the panel and it's stuff blocked some of the noise from that fan motor up front. The decibels also dropped pretty steadily as it moved aft in the long PA32. I didn't find much increase around the door seams.

If there was any take away it was that when I update my windows / windscreen I may go a little thicker. Also good carpeting and maybe some added insulation on the floor / firewall of the cargo space may provide some help.

This will be interesting to do on my A36.. In a few weeks I will have all new glass installed. 3/8 front 3 and 1/4 on the back 6. will see if it makes a difference.

Do these apps have enough repeatability to compare a measurement to one taken later by same phone/app?

For example, if I measured my cabin, then adjusted some of the interior fit to close gaps or whatnot, then measured again - would the results be accurate enough to know whether I had accomplished anything? Or is the repeatability poor even with the same phone and app?