Sound Meter App???

That's the one I have.  Even use it for some general, non critical measurements at work.

I use "Audio Tools" from http://www.studiosixdigital.com

One of the audio ops for CBS was using the Audio Tools app in the main audio room in our newly built truck for them...needless to say he was quite happy with the lack of external noise and dead board level.  Something that is extremely hard to get rid of in a mobile unit that has an air conditioning unit running, equipment fans, and external street noise.

I ran a 7-car passenger train behind the 4-6-0 at 45mph and the highest reading I got was 75db, said that equaled the sound inside a moving car.

I also downloaded a couple of apps for a stopwatch and a distance/time/speed calculator.

With my steamers being under battery power now I no longer have the DCS handheld readout that gave me a smph reading.  After doing all this I realized under DCS I was looking at the readout more than I was at the moving train, to me a moving train appears faster than it's actually going.  My remote control handheld transmitter only has a knob and some pushbuttons.  The 45mph equals 75 degrees of turn on the throttle knob.  When running just the engine 75 degrees equals 55mph.

I wish I had had a sound meter before I ballasted the track, I know it was quieter but I'd like to have a figure.