Punita G. Singh

Studies in auditory timing: 1. Simple patterns

Listeners’ accuracy in discriminating one temporal pattern from another was measured in three psychophysical experiments. When the standard pattern consisted of equally timed (isochronic brief tones, whose interonset intervals (IOIs) were 50, 100, or 200 msec, the accuracy in detecting an asynchrony or deviation of one tone in the sequence was about as would be predicted from older research on the discrimination of single time intervals (6%–8% at an IOI of 200 msec, 11%–12% at an IOI of 100 msec, and almost 20% at an IOI of 50 msec). In a series of 6 or 10 tones, this accuracy was independent of position of delay for IOIs of 100 and 200 msec. At 50 msec, however, accuracy depended on position, being worst in initial positions and best in final positions. When one tone in a series of six has a frequency different from the others, there is some evidence (at IOI = 200 msec) that interval discrimination is relatively poorer for the tone with the different frequency. Similarly, even if all tones have the same frequency but one interval in the series is made twice as long as the others, temporal discrimination is poorer for the tones bordering the longer interval, although this result is dependent on tempo or 101. Results with these temporally more complex patterns may be interpreted in part by applying the relative Weber ratio to the intervals before and after the delayed tone. Alternatively, these experiments may show the influence of accent on the temporal discrimination of individual tones.

The role of timbre, pitch, and loudness changes in determining perceived metrical structure

The role of differences in pitch, loudness, and timbre as determinants of metrical structures was investigated. A repeated sequence of 12 pure tones was systematically partitioned into 4 groups of 3 tones or 3 groups of 4 tones by introducing changes in F0, intensity, and spectral complexity between sounds at serial positions 1, 4, 7, 10 or 1, 5, 9, respectively. Listeners used a rating scale to indicate if a triple, quadruple, or ambiguous meter was perceived. For changes in only one parameter at a time, perception of rhythmic structure followed the physical markers. When changes in more than one parameter were made concurrently, multiple cues for triple or quadruple meter were available. Coincident changes led to reinforcement of the rhythm demarcated by the points of change. Conflicting changes led to different outcomes: Timbre and pitch changes dominated over a loudness‐based accent structure. Pitch versus timbre stimuli were rated as having ambiguous meter. A combination of any two parameters versus ...

Interaction of timbre and pitch in spectral discrimination tasks using complex tones

The dual nature of pitch (“spectral”/“virtual”) and its relation to such timbral percepts as “sharpness” and “roughness” is explored in a set of experiments designed to ascertain perceptual cues facilitating discrimination tasks with complex tones having flat spectral envelopes. Three types of complexes are employed: (1) harmonic “residue” tones comprising four harmonics, (2) ten‐component harmonic and inharmonic complexes with all components shifted from some reference frequency, and (3) ten‐component complexes with a single component shifted from its harmonic frequency. Using two‐tone sequences as stimuli, listeners are asked to judge if the second tone is (1) the same, (2) higher in pitch, (3) lower in pitch, (4) different in “something else,” (5) different in “something else” and higher, or (6) diffferent in “something else” and lower in pitch than the first (“something else” is taken to be synonymous with “timbre”). For residue tones, data indicate that changes in spectral locus yield changes in timb...

Pitching timbre analogies with David Wessel

Contemporary thinking and research on timbre and its use as a dynamic, structural component in music performance have been profoundly influenced by the insights and insounds of David Wessel. His intrepid and creative approach opened up vistas of timbre spaces navigable through multidimensional trajectories. Wessel’s experiments with timbre streaming [Computer Music J. 3, 4552, (1979)] inspired my own work on perceptual organization of complex-tone sequences [Singh, J. Acoust. Soc. Am. 82, 886-899 (1987)]. The finding of a timbre “interva” akin to a pitch interval as a threshold for streaming reinforced Wessel’s notion of timbral analogies [Ehresman and Wessel, IRCAM Rep 13/78, (1978)]. Later work on measuring timbre differences through FO thresholds for streaming (Singh and Bregman, J. Acoust. Soc. Am. 102(4), 1943-1952, (1997)) also lent support to the idea of intervallic relationship between timbres. More recently, my work relating Auditory Scene Analysis to Hindustani rhythms brought us together again,...

The contribution of spectrum and tempo to auditory streaming of simple and compound “bols” in tabla rhythms

Rhythms on the tabla, a north Indian percussion instrument, are generated by producing sounds on one or two drums separately or simultaneously to produce simple or compound “bols.” At high speeds, auditory stream segregation based on spectral properties of adjacent bols can create parallel perceptual layers that can be leveraged strategically by percussionists. This observed phenomenon was studied experimentally by constructing sequences of bols in which adjacent sounds shared different spectral regions. For example, the bols “ghe” and “tin,” which have very different spectra, were placed on either side of the compound bol “dhin,” which contains both “ghe” and “tin.” At a moderate tempo, the sequence is typically heard as a gallop rhythm. However, at quicker tempi, streaming occurs and components of the compound bol “dhin” group perceptually with their neighboring counterparts, to create parallel layers of pairs of “ghe,” “ghe” and “tin,” “tin”, instead of the galloping triple. Listeners identified when s...

Analysis of rhythm performance strategies on the Indian tabla as a function of tempo

In north Indian classical music, the range of tempi can extend from the ultra-slow ‘vilambit’ at less than a beat every 5 seconds to the super-fast ‘drut’ at over 10 beats per second. To hold a rhythm at these speeds and generate a perceptible metrical structure, performers routinely alter playing strategies that derive from neurophysiological and psychoacoustical considerations. At slow speeds, theoretically silent intervals are in practice punctuated by filler sounds to maintain perceptual connectivity. At high speeds, an interesting phenomenon is observed as compound sounds or ‘bols’ segregate into their simpler components, forming auditory streams of acoustically similar sounds. Compound bols such as ‘dha’ break up into the tonal ‘ta’ and the noisy ‘ghe’, with the sequence of rapidly recurring ‘ghe’ sounds forming a noise band that could potentially mask tonal accent markers. To avoid this, performers routinely drop out the ‘ghe’ sounds at high speeds at metrically unimportant points in the sequence, ...

Transcending boundaries with Ira Hirsh

Ira Hirsh has made many contributions to various fields of acoustics from speech, hearing, psychological and physiological acoustics, to musical and architectural acoustics. It was a privilege for me to have been his student in all these areas, and to have had him as a guide through masters and doctoral degree programs that focused on topics that lie at the boundaries connecting these disciplines. Ira was not a prescriptive advisor, imposing particular research topics or procedures on his graduate students. Rather, he encouraged originality, innovation, and personal goal setting. He would subtly suggest starting points and provide landmarks as references, rather than explicit directions leading to them. One had to navigate the path by ones own wits. This approach encouraged lateral, out‐of‐the box thinking, while also leading to respectful appreciation of historic trajectories in scientific research. During our time together, we worked on several aspects of music, including, rhythm, melody, pitch, and tim...

Parsing complex rhythmic structures: The contribution of spectral and temporal dimensions of timbre

Perceptual parsing of sequences with multiple possible metric interpretations was studied. Sequences of 12 complex tones were used as stimuli, with either no deliberate accents provided, or physical accents introduced by changing timbre at positions implying a triple, quadruple, or multiple meter (i.e., both triple and quadruple simultaneously). Subjects reported if they perceived a triple meter, quadruple meter, ambiguous meter, or no meter. The number of harmonics (2, 4, or 8) or the locus of three harmonics were the spectral variables used to mark timbre accents. Steepness of rise and decay time (95+5 ms versus 5+95 ms) was the temporal variable used. These attributes served well as accent markers for sequences with unambiguous meters. However, listeners were generally unable to parse sequences where multiple meters were provided by the same timbre cue. For sequences where multiple meters were provided by contrasting timbres, listeners generally picked the metrical structure implied by spectrally riche...

Perception of rhythm by children in multitimbral, multimetric contexts

Perception of meter by children aged 6 to 12 was studied using sequences of 12 tones as stimuli. Either no accents, or physical accents at positions implying triple, quadruple, or both meters were provided by changing the spectral locus of four harmonics n, n+1, n+2, n=3, of tones Ln (where n=2 or 6) or the rise/decay times of their temporal envelopes (95+5 ms, vs 5+95 ms). Listeners reported if they perceived a triple, quadruple, or ambiguous meter, or no accents at all. Children were easily able to perceive the metrical structure of sequences with accents on triple or quadruple meter positions alone. Mixed meters were hard to parse in a single‐timbre context. In mixed sequences with accents provided by different timbre features at quadruple and triple meter positions, listeners tended to follow the meter implied by tones L2 rather than L6. Temporal envelope variables were not effective in facilitating parsing of mixed meters. Results indicate that young listeners are similar to adults in using timbral i...

An investigation of different timbral attributes as markers determining metrical structure

Timbre attributes such as spectral locus, spectral density, and temporal envelope slope were studied to determine their relative effectiveness as accent markers defining metrical structure. Complex‐tone sequences comprising 12 tones were used as stimuli with points of timbre change at positions implying a triple meter, quadruple meter, compound meter (both triple and quadruple), or unaccented sequences with no timbre changes. Tones at accented positions were made to differ from the rest by using different spectral densities (1, 2, 4, or 8 harmonic components), by changing the locus of components, and by changing the slopes of a two‐part temporal amplitude envelope. Listeners were asked to report if the sequence had a triple meter, quadruple meter, ambiguous meter, or no meter. Results thus far indicate that each of the timbre markers used is individually capable of bestowing metrical structure on a sequence. However, when competing cues exist to offer alternative interpretations of meter, more dense spect...