Biomedical subjects

J J DiGiovanni

Publications and source records attributed to J J DiGiovanni.

3 recordsLinked to original sources

PubMed2001

Duration discrimination and subjective duration for ramped and damped sounds.

The perception of stimuli with ramped envelopes (gradual attack and abrupt decay) and damped envelopes (abrupt attack and gradual decay) was studied in subjective and objective tasks. Magnitude estimation (ME) of perceived duration was measured for broadband noise, 1.0-kHz, and 8.0-kHz tones for durations between 10 and 200 ms. Damped sounds were judged to be shorter than ramped sounds. Matching experiments between sounds with ramped, damped, and rectangular envelopes also showed that damped sounds are perceived to be shorter than ramped sounds, and, additionally, the reason for the effect is a result of the damped sound being judged shorter than a rectangular-gated sound rather than the ramped sound being judged longer than a rectangular-gated sound. These matching studies also demonstrate that the size of the effect is larger for tones (factor of 2.0) than for broadband noise (factor of 1.5). There are two plausible explanations for the finding that damped sounds are judged to be shorter than ramped or rectangular-gated sounds: (1) the abrupt offset at a high level of the ramped sound (or a rectangular-gated sound) results in a persistence of perception (forward masking) that is considered in judgments of the subjective duration; and (2) listeners may ignore a portion of the decay of a damped sound because they consider it an "echo" [Stecker and Hafter, J. Acoust. Soc. Am. 107, 3358-3368 (2000)]. In another experiment, duration discrimination for broadband noise with ramped, damped, and rectangular envelopes was studied as a function of duration (10 to 100 ms) to determine if differences in perceived duration are associated with the size of measured Weber fractions. A forced-choice adaptive procedure was used. Duration discrimination was poorer for noise with ramped envelopes than for noise with damped or rectangular envelopes. This result is inconsistent with differences in perceived duration and no explanation was readily apparent.

Adult↗

PubMed1999

Masker laterality and cueing in forward-masked intensity discrimination.

Forward-masked intensity discrimination was measured as a function of level in experiments designed to reveal insights into the mechanism(s) underlying the midlevel elevation of the Weber fraction. The standard and maskers were 1.0-kHz tones that were separated by 100 ms. Performance was measured for listeners with normal hearing using an adaptive procedure. In experiment 1, intensity discrimination was measured in the presence of an ipsilateral masker (80 dB SPL), a contralateral masker (93 dB SPL), and a binaural (dichotic) masker produced by combining the ipsilateral and contralateral maskers. Listeners perceived only the contralateral masker in the binaural-masker condition. The contralateral masker produced a small midlevel elevation of the Weber fraction. The ipsilateral masker and the binaural masker produced a large, midlevel elevation of the Weber fraction. Experiment 2 found that a two-tone masker resulted in a reduction (improvement) in the Weber fraction for some conditions, but the midlevel elevation remained for all subjects in this cue-tone condition. Experiment 3 demonstrated that cross talk could not account for all of the masking observed with contralateral maskers. Taken together, the results suggest that a single complex mechanism or multiple mechanisms may be responsible for the masking seen in these experiments. On the basis of the cueing results, it is concluded that a portion of the masking is due to cognitive factors; however, a sensory mechanism cannot be ruled out for the remaining portion, based on the results of these experiments. Finally, a small but significant amount of masking due to contralateral maskers places the mechanism for this outcome central to the cochlear nucleus.

Adult↗

PubMed1998

Basilar membrane nonlinearity and loudness.

Loudness matching functions for tones for persons with one shifted-threshold ear (hearing loss and noise-shifted thresholds) and one ear within normal limits were used to derive the presumed basilar membrane (BM) input-output (I/O) function in a normal ear. The comparison was made by assuming that the BM I/O function for the ear with the cochlear threshold shift has a slope of one (a linearized cochlea). The function for the normal ear was derived from the loudness matching function based on this assumption. Comparisons were made for archival basilar membrane data [M. A. Ruggero, N. C. Rich, A. Recio, S. S. Narayan, and L. Robles, J. Acoust. Soc. Am. 101, 2151-2163 (1997)] for chinchilla and archival loudness matches for long-duration tones for persons with various degrees of cochlear hearing loss [F. Miskolczy-Fodor, J. Acoust Soc. Am. 32, 486-492 (1960)]. Comparisons were made also between BM I/O functions and ones derived from loudness matches for persons with unilateral hearing loss simulated by broadband noise. The results show a close resemblance between the basilar membrane I/O function and the function derived from loudness matches for long-duration tones, even though the comparison was between human and chinchilla data. As the degree of threshold shift increases from 40 to 80 dB, the derived BM I/O functions become shallower, with slopes for losses of 60 dB or more falling in the range of values reported for physiological data. Additional measures with short-duration tones in noise show that the slope of the loudness function and the slope of the derived basilar membrane I/O function are associated with the behavioral threshold for the tone. The results for long-duration tones suggest a correspondence between BM displacement and loudness perception in cases of recruitment, but the relation between the degree of loss and the amount of BM compression and the relation between signal duration and compression suggests that other factors, such as the neural population response, may play a role.

Adult↗