The perceptual segregation of simultaneous vowels with harmonic, shifted, or random components

Abstract

This experiment was an investigation of the ability of listeners to identify the constituents of double vowels (pairs of synthetic vowels, presented concurrently and binaurally). Three variables were manipulated: (1) the size of the difference in FO between the constituents (0, lh, and 6 semitones); (2) the ft'equency relations among the sinusoids making up the constituents: harmonic, shifted (spaced equally in frequency but not integer multiples ofthe FO), and random; and (3) the relationship between the FO contours imposed on the constituents: steady state, gliding in parallel, or gliding in opposite directions. It was assumed that, in the case of the gliding contours, the harmonics of each vowel would "trace out" their spectral envelope and potentially improve the definition of the formant locations. It was also assumed that the application of different FO contours would introduce differences in the direction of harmonic movement (common fate), thus aiding the perceptual segregation of the two vowels. The major findings were the following: (1) For harmonic constituents, a difference in FO leads to improved identification performance. Neither tracing nor common-fate differences add to the effect of pitch differences. (2) For shifted constituents, a difference between the spacing of the constituents also leads to improved performance. Formant tracing and common fate contribute some further improvement. (3) For random constituents, tracing does not contribute, but common fate does.In most listening situations, we rarely hear a single sound in complete isolation. Several sound sources are often active at the same time, producing a complex pattern of vibrations on our eardrums. The auditory system is, therefore, faced with the problem of distinguishing the different sets of components that correspond to separate sound sources. Otherwise, it would not be possible to understand, for example, what one speaker is saying in the presence of competing speakers or background noises.Different experiments have studied the ability to selectively attend to one speech signal in a mixture of continuous speech signals (Broadbent, 1952;Brokx & Nooteboom, 1982;Cherry, 1953;Darwin, 1981). These studies have suggested that perceptual separation can improve when the signals have different pitches. Scheffers (1983) investigated the effects of fundamental frequency (FO) differences on the identification of two simultaneous steadystate synthetic vowels and confirmed the hypothesis that the two vowels can be more easily separated when the FOs differ by more than 1-2 semitones. Listeners' ability to identify both vowels improved by about 18 % with dif-

The mutual roles of temporal glimpsing and vocal characteristics in cocktail-party listening

“…While there are many studies showing that performance in a concurrent-speech task improves when there is a pitch difference between the competing voices (e.g., Brokx and Nooteboom, 1982;Chalikia and Bregman, 1993;Qin and Oxenham, 2005;Assmann and Summerfield, 1990;Assmann and Summerfield, 1994;Culling and Darwin, 1993), there are relatively few studies on the role of VTL (Vestergaard et al, 2009a;Vestergaard and Patterson, 2009;Darwin et al, 2003;Ives et al, 2010). De Cheveigné and colleagues have argued that the pitch advantage depends primarily on the harmonicity of the distracter (de Cheveigné et al, 1997b(de Cheveigné et al, , 1997ade Cheveigné, 1997de Cheveigné, , 1993.…”

Grouping and the pitch of a mistuned fundamental component: Effects of applying simultaneous multiple mistunings to the other harmonics

“…This manipulation was originally suggested by the first author toChalikia and Bregman (1993). They used it to produce vowel-like stimuli with randomly perturbed harmonics that maintained the same average spectral density as their harmonic counterparts.…”

Dependence of frequency modulation detection on frequency modulation coherence across carriers: Effects of modulation rate, harmonicity, and roving of the carrier frequencies

“…While some studies have been interpreted as indicating a weak sensitivity to FM coherence ͑Cohen and Chen, 1992; Chalikia and Bregman, 1993͒, the majority of studies have failed to indicate such sensitivity. These studies have been reviewed in an earlier paper ͑Furukawa and Moore, 1996͒.…”

“…Evidence for sensitivity to FM coherence has been sought using paradigms such as modulation detection/ discrimination interference ͑Wilson et al Moore et al, 1991;Carlyon, 1992, comodulation masking release ͑CMR͒ ͑Schooneveldt and Moore, 1988;Hall, 1990͒, CMR interference ͑Grose et al, 1995͒, discrimi-nation between coherent and incoherent FM ͑Grose and Carlyon, 1991͒, segregation of competing vowels ͑McAdams, 1989Marin and McAdams, 1991;Summerfield and Culling, 1992;Chalikia and Bregman, 1993;Culling and Summerfield, 1995͒, effects of FM coherence on signal detectability ͑Cohen and Chen, 1992;Carlyon, 1994͒, and the shift of the first formant phoneme boundary ͑Gardner and Darwin, 1986͒. While some studies have been interpreted as indicating a weak sensitivity to FM coherence ͑Cohen and Chen, 1992; Chalikia and Bregman, 1993͒, the majority of studies have failed to indicate such sensitivity.…”