An apparatus for the remote monitoring of audio signals, such as radio broadcasts or the audio portion of television broadcasts, includes a portable transponder intended to be worn or carried by a potential audience member and a receiver. The receiver contains circuitry for perceiving audio present in a monitored region and identifying an audio signal of interest. It also contains circuitry for detecting the presence of the transponder in the monitored region and creating a record associating the dwell time of the transponder and thus the audience member in the monitored region with the audio signal.