Frequency‐Response Characteristic of Auditory Observers Detecting Signals of a Single Frequency in Noise: The Probe‐Signal Method

Four experiments were conducted to develop and test a method of determining the frequency‐response characteristic of the observer when he listens for single‐frequency signals presented against a continuous background of wide‐band noise. After observers were trained to detect primary signals of a single frequency, probe signals of various other frequencies were presented infrequently, in lieu of the primary signal. Primary signals and all probe signals were presented with very similar amplitudes that would be expected to render them all equally detectable if presented alone in single‐frequency experiments. Estimates of the detectability of the signals of the various frequencies were obtained concurrently in a two‐alternative forced‐choice procedure. The results from 14 observers were quite similar and show differences in detection as a function of signal frequency when the primary signal was of 1000 or of 1100 Hz. In general, the primary signal was correctly detected 75%–90% of the time while signals with frequencies at approximately 150 to 200 Hz on either side of the primary‐signal frequency were detected at the chance level, 50% correct. In as few as three experimental sessions, the observer's frequency‐response characteristic was obtained using the probe‐signal method.