Since no audio person went on the trip, it's difficult to know what all happened. We weren't even consulted, sadly. The video guy took some of the equipment we usually use for location recordings and used it as-is. I'll have to wait for the equipment to be returned to get the exact wireless frequency, but it was in the 400-500 MHz range.
RX has a good Spectrum Analyzer. Your pointer will snap to high amplitude components and read out the exact frequency. I set the FFT to 16348. The tone is similar to a gently distorted, filtered square wave with a 3120 Hz fundamental. Strong odd harmonics, much softer even harmonics. Steady pitch, with amplitude slightly modulated by the signal.
Here's a screenshot of a portion of one of the files.
https://www.dropbox.com/s/t59p3qe7ug...tones.png?dl=0