Impact sounds were synthesized according to standard textbook equations given for the motion of simply supported, metal plates. In a two-interval, forced-choice procedure, highly practiced listeners identified from these sounds a predefined class of target plates based on their particular material and geometric properties. The effects of two factors on identification were examined: the relative level of partials comprising the sounds and the relative amount of information ͑given as the difference in dЈ͒ each partial provided for identification. In different conditions one factor was fixed while the other either increased or decreased with frequency. The effect on listener identification in each case was determined from a logistic discriminant analysis of trial-by-trial responses, yielding a vector of listener decision weights on the frequency and decay of individual partials. The weights increased proportionally with relative level, but were largely uninfluenced by relative information content-a result exactly opposite to that expected from a maximum-likelihood observer. The dominant effect of relative level was replicated for other sound sources ͑clamped bars and stretched membranes͒ and was not diminished by randomizing the relative level of partials across trials. The results are taken to underscore the importance of relative level in the identification of rudimentary sound sources.
The auditory discrimination of force of impact was measured for three groups of listeners using sounds synthesized according to first-order equations of motion for the homogenous, isotropic bar [Morse and Ingard (1968). Theoretical Acoustics pp. [175][176][177][178][179][180][181][182][183][184][185][186][187][188][189][190][191]. The three groups were professional percussionists, nonmusicians, and individuals recruited from the general population without regard to musical background. In the two-interval, forced-choice procedure, listeners chose the sound corresponding to the greater force of impact as the length of the bar varied from one presentation to the next. From the equations of motion, a maximum-likelihood test for the task was determined to be of the form Dlog A þ aD log f > 0, where A and f are the amplitude and frequency of any one partial and a ¼ 0.5. Relative decision weights on D log f were obtained from the trial-by-trial responses of listeners and compared to a. Percussionists generally outperformed the other groups; however, the obtained decision weights of all listeners deviated significantly from a and showed variability within groups far in excess of the variability associated with replication. Providing correct feedback after each trial had little effect on the decision weights. The variability in these measures was comparable to that seen in studies involving the auditory discrimination of other source attributes.
A computational formula is derived for estimating the constraints limited auditory sensitivity imposes on auditory identification of the material and geometric properties of struck bars. The formula combines a model of the transverse motion of the bar with empirical psychometric functions to map out "null" regions in the bar's physical parameter space where changes in the frequency, amplitude, and decay of partials are likely below threshold for detection. Parameters of the physical space include bar density, Young's modulus, fluid and viscoelastic damping factors, bar length, and bar cross-sectional area ͑as related to bar shape and hollowness͒. The formula is used to estimate the possible effect of limited sensitivity in past studies on the auditory identification of bar attributes. The results suggest that sensitivity may, indeed, have played a role in some studies, and that apparent discrepancies in results may be understood based on whether the predominant source of damping was internal or external to the bar. The formula identifies conditions representing an expected bound on identification performance and thereby may be used to aid in the design of future studies for which the struck bar is the sound source of choice.
Spectral density (D), defined as the number of partials comprising a sound divided by its bandwidth, has been suggested as cue for the identification of the size and shape of sound sources. Few data are available, however, on the ability of listeners to discriminate differences in spectral density. In a cuecomparison, forced-choice procedure with feedback, three highly practiced listeners discriminated differences in the spectral density of multitone complexes varying in bandwidth (W ¼ 500-1500 Hz), center frequency (f c ¼ 500-2000 Hz), and number of tones (N ¼ 6-31). To reduce extraneous cues for discrimination, the overall level of the complexes was roved, and the frequencies were drawn at random uniformly over a fixed bandwidth and center frequency for each presentation. Psychometric functions were obtained relating percent correct discrimination to DD in each condition. For D < 0.02 Hz À1, the steepness of the functions remained constant across conditions, but for D > 0.02 Hz À1 , they increased with D. The increase, moreover, was accompanied by a reduction in the upper asymptote of the functions. The data were well fit by a model in which spectral density discrimination is determined by the frequency separation of components on an equivalent rectangular bandwidth scale, yielding a roughly constant Weber fraction of DD/D ¼ 0.3. V
Impact sounds synthesized according to a physical model have increasingly become the stimulus of choice in studies of sound source perception. Few studies, however, have incorporated manner of contact in their models because of the many parameters entailed in its description. Based on the work of Zener [Phys. Rev 669–673 (1941)], we show that the seven Hertzian parameters required to completely describe the contact can be reduced to just three: force of contact, duration of contact (tc) and a non-dimensional parameter (λ). Using only these parameters for the contact, a simplified method is presented to synthesize the impact sounds of simply supported plates. The results of the method are shown to be in good agreement with those of the more comprehensive method of Chaigne and Lambourg [J. Acoust. Soc. Am. 1422–1432 (2001)], the only such method to receive validation through acoustic measurement of plates. Psychometric functions obtained from listeners for the discrimination of tc and λ also show these parameters to be clearly discriminable over the range for which they would realistically vary. Potential advantages of using the simplified method over more comprehensive methods of sound synthesis in perceptual studies are discussed. [Research supported by NIDCD Grant No. 5R01DC006875-05.]
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.