Fig. 1.

Stimulus design. (A) Acoustic waveform (top) and spectrogram (bottom) of one example sentence used to create the stimulus material for the present study. Colored outlines show amplitude envelopes extracted from (here) three logarithmically spaced frequency ranges between 0.2 and 8 kHz (red dashed lines). (B) Stimuli were envelope-modulated band-limited noises differing in the frequency range used to create the noise and the frequency range from which the speech envelope was derived and used to modulate the noise. The figure shows 1 s snippets from stimuli used in Block 1. The spectral ranges covered by the carrier noise and the spectral range from which the envelope was extracted were paired across conditions as shown by the matrix (low: 0.2 - 0.83 kHz, mid: 0.83 - 2.66 kHz and high: 2.66 - 8 kHz). Conditions 1, 3 and 5 (green numbers) reflect natural pairings where the frequency band of the carrier was modulated with the envelope derived from the same band, while conditions 2 and 4 reflect unnatural pairings. (C) Icons are used in the following figures to illustrate how distinct envelope and carrier bands were used to create a specific stimulus condition in the experiment, or to define a factor for data analysis. Envelope-carrier pairs presented in the experiment are marked as filled boxes in the checkerboard. Depending on the experimental blocks, this could be individual (left) or simultaneously presented pairs (middle). For some data analysis we averaged experimental conditions as indicated with a plus symbol between icons (right), or contrasted these as indicated by a minus sign.