All stimuli were generated digitally in MATLAB (The Mathworks, Natick, MA). The stimulus duration was 200 ms, including 40-ms raised-cosine onset and offset ramps. The silent interval between the two intervals within a trial was 500 ms. The stimuli for the context trials containing the noise bands were generated in advance of a block of trials (105 trials). Ten exemplars with four independent noise bands and random starting phases of the remaining components were generated for each of the two F0s, and one of each was chosen at random in each context trial. Each noise band was digitally synthesized by summing sinusoids spaced at 1-Hz intervals over the required frequency range (±5 % of the NCF). The amplitudes were drawn from a Rayleigh distribution, and the phases from a uniform distribution in the range 0–360°. The stimuli were played out using a 16-bit digital-to-analog converter (CED 1401 plus), with a sampling rate of 20 kHz, and passed through an antialiasing filter (Kemo VBF25.01) with a cutoff frequency of 7.5 kHz (slope of 100 dB/octave). The overall level was controlled by Tucker-Davis Technologies (TDT) PA4 attenuators. Stimuli were mixed with a continuous background pink noise (low-pass filtered at 5 kHz, Kemo VBF25.03 filter, slope of 48 dB/octave) with a spectrum level of 13 dB (re 20 μPa) at 1 kHz and passed through a headphone buffer (TDT HB7) before being presented binaurally through Sennheiser HD 650 headphones. Subjects were seated individually in an IAC double-walled sound-attenuating booth.