Can the Shure ULX wireless systems be used for acoustical measurement using sweep tones?
Most wireless microphone systems, Shure and other manufacturers, usually have a slight "rock-and-roll" equalization, i.e., low frequency and high frequency boosts. These systems are not designed to be perfectly flat from 20Hz to 20kHz as required for acoustical measurement.
A sweeped tone is a brutal test for any wireless system. Any slight frequency response imperfection between the compressor output and the expander input will be exaggerated by a factor of the compression/expansion ratio. Since the compression ratio for Shure ULX is about 5:1 with nominal input levels, a sweeped tone will show a frequency response 5 times worse than what you would see with a broadband stimulus. Thus, using the ULX for acoustical measurement is not recommended.