title: Informational masking of monaural target speech by a single contralateral formant.
abstract: Recent research suggests that the ability of an extraneous formant to impair intelligibility depends on the variation of its frequency contour. This idea was explored using a method that ensures interference cannot occur through energetic masking. Three-formant (F1 + F2 + F3) analogues of natural sentences were synthesized using a monotonous periodic source. Target formants were presented monaurally, with the target ear assigned randomly on each trial. A competitor for F2 (F2C) was presented contralaterally; listeners must reject F2C to optimize recognition. In experiment 1, F2Cs with various frequency and amplitude contours were used. F2Cs with time-varying frequency contours were effective competitors; constant-frequency F2Cs had far less impact. To a lesser extent, amplitude contour also influenced competitor impact; this effect was additive. In experiment 2, F2Cs were created by inverting the F2 frequency contour about its geometric mean and varying its depth of variation over a range from constant to twice the original (0%-200%). The impact on intelligibility was least for constant F2Cs and increased up to ∼100% depth, but little thereafter. The effect of an extraneous formant depends primarily on its frequency contour; interference increases as the depth of variation is increased until the range exceeds that typical for F2 in natural speech.
authors.affiliation: Psychology, School of Life and Health Sciences, Aston University, Birmingham B4 7ET, United Kingdom.
authors.forename: Brian
authors.initials: B
authors.lastname: Roberts
authors.affiliation: Psychology, School of Life and Health Sciences, Aston University, Birmingham B4 7ET, United Kingdom.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Summers
mesh_terms: D000161:Acoustic Stimulation; D000162:Acoustics; D000293:Adolescent; D000328:Adult; D001302:Audiometry, Speech; D005260:Female; D006801:Humans; D008297:Male; D010470:Perceptual Masking; D021641:Recognition, Psychology; D013018:Sound Spectrography; D013061:Speech Acoustics; D013065:Speech Intelligibility; D013067:Speech Perception; D013997:Time Factors; D055815:Young Adult