Prolonged listening to a pulse train with repetition rates around 100 Hz induces a striking aftereffect, whereby subsequently presented sounds are heard with an unusually "metallic" timbre [Rosenblith, Science 106, 333-335 (1947)]. The mechanisms responsible for this auditory aftereffect are currently unknown. Whether the aftereffect is related to an alteration of the perception of temporal envelope fluctuations was evaluated. Detection thresholds for sinusoidal amplitude modulation (AM) imposed onto noise-burst carriers were measured for different AM frequencies (50-500 Hz), following the continuous presentation of a periodic pulse train, a temporally jittered pulse train, or an unmodulated noise. AM detection thresholds for AM frequencies of 100 Hz and above were significantly elevated compared to thresholds in quiet, following the presentation of the pulse-train inducers, and both induced a subjective auditory aftereffect. Unmodulated noise, which produced no audible aftereffect, left AM detection thresholds unchanged. Additional experiments revealed that, like the Rosenblith aftereffect, the effect on AM thresholds does not transfer across ears, is not eliminated by protracted training, and can last several tens of seconds. The results suggest that the Rosenblith aftereffect is related to a temporary alteration in the perception of fast temporal envelope fluctuations in sounds.
Bibliographical noteFunding Information:
This work was carried out while the authors were at the Massachusetts Institute of Technology’s Research Laboratory of Electronics, Cambridge, MA. We thank Daniel Pressnitzer for pointing us to the publication of Rosenblith et al. (1947) , and Torsten Dau and Stephan Ewert for generously providing us the code of the modulation filterbank. This research was supported by National Institutes of Health Grant No. R01 DC 03909, Deutsche Forschungsgemeinschaft Grant GU 593/2-1, and the Dietmar-Hopp-Stiftung.