Here's a new one....measuring sound in an aircraft

[pscm]

I recently have picked up a measuring mic and going down the rabbit hole of improvement to my room. I work in the commercial and corporate aircraft maintenance side of the world. We just had a customer approach us about options to lower the db in the cabin of their aircraft that has some economics to it.
In the past we have utilized a company that comes in, flies on the aircraft to take sound readings, makes up a kit based on these readings. We install and then a second flight is done to verify the improvements. This particular company guarantees a 5 db improvement. As you might imagine this is very expensive due to regulations, burn testing, etc. To the tune of $150K.

We have found a vendor that makes a product that based on testing has promise. So this got me to thinking that I would use my mic to go up in the aircraft and take measurements just to see if we could prove the improvement. I am wondering what function in REW would be the best for taking noise measurements to show db and frequencies. Or is this not maybe the best software for this.

 

[The_Nephilim]

Well I would imagine the one thing you could use is would be the SPL Meter. that way you can have a before db reading and after.. that is one thing I can think of that might be useful to you..

 

[sm52]

pscm
I think the RTA button in REW will work for you. But in order to prove your reasoning to people with large instruments, you need to calibrate the level meter in REW. So that your microphone + REW shows the same with the measuring equipment of those people. You also need to calibrate your microphone. So that he correctly catches the entire frequency range.

 

[skid00]

You *can* do a sweep measurement, to see the loudness at each frequency. I'm guessing the RTA panel would be more appropriate.

I'd think you'd want to do a quick RTA during takeoff, at cruise, etc.

I wonder if there's a way to get successive, quick RTA's, to get a 'movie' of SPL changes...

 

[DanDan]

5dB is a single number representation. For this type of work we need a spectrum to include the nuisance value and audibility of the sound. The real SLMs from NTI, Bruel and Kjaer, etc. are megabucks. But studiosixdigital and Faberacoustical have some very useful affordable iOS options.

 

[pscm]

Based on some previous experience, the vendor's scenarios were to get the db down at cruise flight as that is where most of the time is spent. From what I was told, there are to many variables to try and get a perfect cabin in all flight phases. There are typical areas that are known problem areas such as passenger door leakage, aft cabin close to the engines when engines are mounted on the fuselage and cargo areas that can bleed into cabin. One interesting thing that was pointed out, are long haul flights and those low frequencies that you can't hear but over a long period of time actually fatigue the body. At leas this is what I was told anyways. We did a combination of mass load suppresion and then soft insulation. To the point mentioned about 5db being a representation, this is absolutely true. It is a case of not just sound but what frequency and how to address it and addressing those that create discomfort. If anything I would like the opportunity to do some tests. If anything to see what it looks like and share with the group. There are indeed many companies far more knowledgeable than I to address this although I sense a bit of snake oil from some of them.