Search

Temporal resolution is often measured using the detection of temporal gaps or signals in temporal gaps embedded in long-duration stimuli. In this study, psychoacoustical paradigms are developed for measuring the temporal encoding of transient stimuli. The stimuli consisted of very short pips which, in two experiments, contained a steady state portion. The carrier was high-pass filtered, dynamically compressed noise, refreshed for every stimulus presentation. The first experiment shows that, with these very short stimuli, gap detection thresholds are about the same as obtained in previous investigations. Experiments II and III show that, using the same stimuli, temporal-separation thresholds and duration-discrimination thresholds are better than gap-detection thresholds. Experiment IV investigates the significance of residual spectral cues for the listeners' performance. In experiment V, temporal separation thresholds were measured as a function of the signal-pip sensation level (SL) in both forward- and backward-masking conditions. The separation thresholds show a strong temporal asymmetry with good separation thresholds independent of signal-pip SL in backward-masking conditions and increasing separation thresholds with decreasing signal-pip SL in forward-masking conditions. A model of the auditory periphery is used to stimulate the gap-detection and temporal-separation thresholds quantitatively. By varying parameters like auditory-filter width and transduction time constants, the model provides some insight into how the peripheral auditory system may cope with temporal processing tasks and thus represents a more physiology-related complement to current models of temporal processing.

Temporal integration is a crucial feature of auditory temporal processing. We measured the psychophysical temporal integration of acoustic intensity in the echolocating bat Megaderma lyra using a two-alternative forced-choice procedure. A measuring paradigm was chosen in which the absolute threshold for pairs of short tone pips was determined as a function of the temporal separation between the pips. The time constants determined with this paradigm are a crucial characteristic of the sonar system of M. lyra, a species orientating in its environment by very short broadband sonar calls emitted at high rates. Two different carrier frequencies for the tone pips were used to obtain data from the lower and the higher half of the hearing area of M. lyra. Both in the lower and in the higher frequency range, M. lyra showed very short time constants of about 220 microseconds. Our results are comparable to data from the echolocating dolphin, Tursiops truncatus, showing click integration times of about 260 microseconds and to estimates of auditory temporal integration in the context of echo clutter interference in the big brown bat.

An important feature of a Jeffress‐type binaural display is that it not only allows for localization of a single sound source but it also allows for resolution of multiple sound sources. Here an experiment is reported which directly addresses spatial resolution with a paradigm similar to the notched‐noise paradigm which quantifies spectral resolution. Listeners are required to detect a band‐pass signal at a frontal position in the presence of two independent band‐stop maskers symmetrically arranged around the signal in space and frequency. Data show that signal detection does not improve when the spatial separation between the signal and the maskers is increased from ± 10 to ± 90 deg. When listeners are turned by 90 deg, i.e., the signal is presented from the left, release from masking is only observed when the maskers are moved into the right hemisphere, an effect closely related to BMLDs observed under headphones. The current data show that auditory spatial resolution of simultaneous sound sources is ve...

The auditory system measures time with exceptional precision. Echolocating bats evaluate the time delay between call and echo to measure object range. An extreme and disputed result on ranging acuity was found in the virtual delay jitter experiments. In these studies, echoes with alternating delays were played back to bats, which detected a jitter down to 10 ns, corresponding to a ranging acuity of 1.7 microm. The current study was designed to measure the ranging acuity of the nectarivorous bat Glossophaga soricina under semi-natural conditions. Three free-flying bats were trained to discriminate between a stationary loudspeaker membrane and a membrane sinusoidally vibrating at 10 Hz. At detection threshold, the average peak-to-peak displacement of the vibrating membrane was 13 mm, corresponding to an echo delay jitter of 75 micros. The perceived jitter from call to call, which depends on the pulse interval and the call emission time relative to the membrane phase, was simulated for comparison with the virtual jitter experiments. This call-to-call jitter was between 20 to 25 micros (ca. 4 mm ranging acuity). These thresholds between 20 and 75 micros (4-13 mm) fall within both ecologically and physiologically plausible ranges, allowing for sufficiently precise navigation and foraging.

ITDs are recruited to localize sounds in azimuth. ITDs can be extracted from low‐frequency sounds or from the envelopes of high‐frequency, complex sounds. Studies of the latter have included amplitude‐modulated or transposed tones. A recent study showed that not the degree of envelope fluctuation, as quantified by the envelope 4th moment, determines sensitivity to envelope ITDs but the envelope spectrum and with it the interaural cross‐correlation function of the auditory envelopes provide a good description of envelope ITD sensitivity. Here we use a different class of high‐frequency stimuli, namely noise stimuli generated with different degrees of roughness which resemble natural rustling sounds. Stimuli are generated with a Gaussian‐noise carrier and an aperiodic, rectangular modulator of statistically different duty cycle. The results show that ITD sensitivity increases both with increasing roughness and increasing bandwidth of the rustling sounds. While the effect of bandwidth on ITD sensitivity is in...

This study uses rippled noise and ‘‘AABB’’ noise [Wiegrebe et al., J. Acoust. Soc. Am. 104, 2307–2313 (1998)] to investigate time constants associated with pitch processing in the auditory system. RN and AABB have identical long‐term spectra and autocorrelations but they differ in their temporal dynamics. Previously, it was shown that, when the pitch of the stimuli is below about 350 Hz, listeners could discriminate broadband AABB from RN based on a pitch‐strength difference. Here, the effect of frequency passband on the RN‐AABB discrimination was investigated. In each 1‐kHz band, discrimination performance decreased with decreasing delay (32–4 ms). As the center frequency increased from 0.5 to 4 kHz, the rate of decrease became smaller such that discrimination was still significant in the highest band with the shortest delay. Further experiments suggest that the RN‐AABB discrimination and its frequency effects are based on pitch‐strength differences. Auditory simulations suggest that integration of pitch...