title: Mechanisms underlying the detection of frequency modulation.
abstract: Frequency modulation detection limens (FMDLs) were measured for carrier frequencies (f(c)) of 1000, 4000, and 6000 Hz, using modulation frequencies (f(m)) of 2 and 10 Hz and levels of 20 and 60 dB sensation level (SL), both with and without random amplitude modulation (AM), applied in all intervals of a forced-choice trial. The AM was intended to disrupt excitation-pattern cues. At 60 dB SL, the deleterious effect of the AM was smaller for f(m) = 2 than for f(m) = 10 Hz for f(c) = 1000 and 4000 Hz, respectively, while for f(c) = 6000 Hz the deleterious effect was large and similar for the two values of f(m). This is consistent with the idea that, for f(c) below about 5000 Hz and f(m) = 2 Hz, frequency modulation can be detected via changes in phase locking over time. However, at 20 dB SL, the deleterious effect of the added AM for f(c) = 1000 and 4000 Hz was similar for the two values of f(m), while for f(c) = 6000 Hz, the deleterious effect of the AM was greater for f(m) = 10 than for f(m) = 2 Hz. It is suggested that, at low SLs, the auditory filters become relatively sharp and phase locking weakens, so that excitation-pattern cues influence FMDLs even for low f(c) and low f(m).
authors.affiliation: Department of Experimental Psychology, University of Cambridge, Downing Street, Cambridge CB2 3EB, United Kingdom. sme30@cam.ac.uk
authors.forename: Stephan M A
authors.initials: SM
authors.lastname: Ernst
authors.forename: Brian C J
authors.initials: BC
authors.lastname: Moore
mesh_terms: D000161:Acoustic Stimulation; D001299:Audiometry; D001306:Auditory Pathways / Q000502:physiology*; D001309:Auditory Threshold; D003463:Cues; D006801:Humans; D008962:Models, Theoretical; D010897:Pitch Discrimination; D011571:Psychoacoustics; D017603:Signal Detection, Psychological; D013997:Time Factors