Loudness Balances Employing Signals with Unequal Duty Cycles

The alternate binaural loudness balance technique was employed to investigate the effects of duty cycle (the percentage of time the sound is on) upon the perceived magnitude of 1000-Hz pure-tone signals. The reference signal was fixed in the right ear at 50-dB sound-pressure level (SPL). In the left ear, the comparison signal intensity was adjusted via a Békésy audiometer to yield equal interaural loudnesses. The loudness of interrupted signals increased as the signal duty cycle was increased. A low-duty-cycle comparison signal was consistently judged to be softer than an equally intense high-duty-cycle reference signal. Furthermore, a high-duty-cycle comparison signal was consistently judged louder than a low-duty-cycle reference signal of the same intensity. The greatest interaural loudness disparity was observed for the experimental conditions in which the interaural duty-cycle difference (high duty cycle minus low duty cycle) was 80%. During a substantial number of trials, this relationship between duty cycle and loudness increased in magnitude throughout the 4-min balancing period. Duty-cycle-loudness effects were enhanced when a 400-msec silent interval separated alternating tones. The results of this study may be incorporated to assist in the explanation of the occurrence of the type-V Békésy pattern in clinical audiology. In addition, they lead to questions concerning the interpretation of experiments in which interrupted signals are presented for loudness evaluation such as experiments on loudness adaptation.