Audix TR40 Details Test and measurement microphone for RTA and room analysis software systems. The Audix TR40 microphone is the first in a series of test and recording microphones specially designed by Audix. The Audix TR40 features a quarter-inch diameter pre-polarized condenser capsule with omnidirectional polar pattern. It delivers the extremely linear frequency response characteristics that audix microphones are known for worldwide. Frequency response is 20Hz-19kHz (+/- 1dB). Many engineers prefer the phase coherent response that a mic such as the TR40 delivers. Its omnidirectional capsule is ideal for certain studio and live recording applications, such as piano, musical ensembles, and choirs