Low-frequency harmonic complexes and transposed high-frequency tones isolate phase-locking cues for lateralization tests

Evidence

The main four tasks (namely, ITD, ILD, TIME , and LEVEL tasks) employed two types of stimuli, referred to as the lowand high-frequency stimuli, which were identical to those used in our earlier study (Ochi et al. 2014 ) and are thus only described briefly here. The stimuli were designed to assess the listener’s ability to use information on the basis of neural phase-locking to the stimulus temporal structure, respectively, in the ITD and TIME tasks. Essentially the same stimuli were also used in the ILD and LEVEL tasks. The low-frequency stimulus was a spectrally shaped multicomponent complex (SSMC), which was a harmonic complex with a fundamental frequency (F 0 ) of 100 Hz. The spectral envelope had a flat passband and sloping edges (5×F 0 centered at 1100 Hz).The overall level of the complex was 54 dB SPL. Threshold equalizing noise, extending from 125 to 15,000 Hz, was added. The high-frequency stimulus was a ˵transposed stimulus,˶ which was a 4-kHz tone carrier amplitude-modulated with a half-wave rectified 125-Hz sinusoid (Bernstein and Trahiotis 2002 ). It is considered that the auditory-nerve firing is phase locked to the modulator waveform, which provides the cue for judging the ITD and modulation rate of the stimulus. The overall level of the transposed stimulus was set to 65 dB SPL. A continuous, low-pass filtered Gaussian noise was added to prevent the listener from using any information at low spectral frequencies (e.g., combination tones). — Dijk, Pim van, Physiology, Psychoacoustics and…, 1041

Categorization

• DEFINE: Defines the spectrally shaped multicomponent complex and the transposed stimulus, two core stimulus types used in lateralization research.