N1m as a function of stimulus type. (A, B) Acoustic waveforms (upper graphs) and spectrograms (lower graphs) of the vowel (A) and sine tone stimulus (B). In this spectrogram, the acoustic energy in a certain frequency band and at a certain time point is proportional to the darkness of the grey shading. (C, D) Mean ± SD amplitudes of the four consecutive N1m peaks for the vowel (C) and the tone (D) conditions are presented (n = 15). The N1m peak amplitudes in the grand average of vowel and tone stimulation are displayed in Figure 2A.