Enhancing and unmasking the harmonics of a complex tone

Abstract

Alternately eliminating and reintroducing a particular harmonic of a complex tone can cause that harmonic to stand out as a pure tone-separately audible from the rest of the complex-tone background. In the psychoacoustical literature the effect is known as "enhancement." Pitch matching experiments presented in this article show that although harmonics above the 10th are not spectrally resolved, harmonics up to at least the 20th can be enhanced. Therefore, resolution is not required for enhancement. Further, during those experimental intervals in which a harmonic is eliminated, excitation pattern models suggest that listeners should be able to hear out a neighboring harmonic-separately audible from the background. The latter effect has been called "unmasking." In the present article we provide the first experimental evidence for unmasking. Harmonics of 200 Hz, with harmonic numbers between about 5 and 16, are readily unmasked. Their pitches are usually matched by sine tones with frequencies that are not exactly those of the unmasked harmonics but are shifted in a direction away from the frequency of the pulsed harmonic. Phase relationships among the harmonics that produce temporally compact cochlear excitation lead to reduced enhancement but greater unmasking.

The salience of enhanced components within inharmonic complexes

“…Across-segment comparisons may partially account for the salience responses of the typical enhancement stimuli (FWD) as well as the presence of enhancement in conditions where adaptation-ofinhibition should not be as effective, e.g., the BWD conditions. [For the BWD conditions, a salient pitch at the edge of the spectral notch (using harmonic complexes; Hartmann and Goupell, 2006) may have also somewhat affected the salience responses. ]…”

Grouping Mechanisms in Music

“…If a particular harmonic of a complex tone is alternately omitted and restored, this can cause it to stand out as a pure tone, separately audible from the remainder of the complex, and it can even be heard for a short time after being turned back on (Hartmann & Goupell, 2006;Houtsma, Rossing, & Wagenaars, 1987). Darwin and Ciocca (1992) have shown that onset asynchrony can influence the contribution made by a mistuned harmonic to the pitch of a complex.…”

The perception of concurrent sound objects through the use of harmonic enhancement: a study of auditory attention

“…However, they also proposed that when a harmonic is omitted, the masking effect on neighboring harmonics caused by the now omitted harmonic is reduced, consistent with the adaptation of an inhibition model suggested by Viemeister and Bacon (1982). Hartmann and Goupell (2006) suggested the involvement of selective attention in enhancement; although they noted that its role was not yet clear.…”

“…Importantly, the ongoing enhancement effect provides an input for downstream processing based on object-based accounts of auditory attention (Alain & Arnott, 2000;Shinn-Cunningham, 2008), which supposes that the enhanced harmonic is perceived as a distinct object. According to this interpretation, transient mistuning causes attention to be shifted to the frequency of the disrupted harmonic, leading to enhancement via one of several possible mechanisms (e.g., Hartmann & Doty, 1996;Hartmann & Goupell, 2006;Lin & Hartmann, 1998;Moore et al, 1986;Viemeister & Bacon, 1982). Ongoing attention to the now-enhanced harmonic would perhaps be facilitated by consequences of temporary attentional facilitation, such as a readjustment of relative amplitudes of neural activity in a network in which frequency-tuned cells have mutually inhibitory connections with neighboring frequencies.…”

“…However, to our knowledge, what happens following the mistuning of a harmonic, in other words the after-effects, has not been examined other than to evaluate the pitch of the enhanced harmonic. Hartmann and Goupell (2006) demonstrated that when a complex sound ended with the pulsed harmonic turned on, the perceived pitch of the harmonic that stands out was close to its original frequency, suggesting this specific harmonic was successfully enhanced. However, they also proposed that when a harmonic is omitted, the masking effect on neighboring harmonics caused by the now omitted harmonic is reduced, consistent with the adaptation of an inhibition model suggested by Viemeister and Bacon (1982).…”