Figure 1.

Within- and between-speaker variability pose a challenge to speech comprehension. (a) A higher-pitch speaker produces two instances of “bat” slightly differently (labeled as utterance 1 and utterance 2), but both speech sequences map onto the same linguistic content. Key within-speaker differences in the speech waveform and spectrogram representation of the acoustic signal include changes in the amplitude of the speech envelope, shifted spectral peaks, and different final phoneme durations. (b) The same speaker as in panel a produces the word “mat.” Corresponding acoustic-phonetic features are shown in the lowest panel, indicating the manner and place of the articulatory gesture that produces the corresponding sound. (c) A different, lower-pitch speaker than the speakers in panels a and b produces the word “bat.” Key between-speaker differences in the speech waveform and spectrogram representation of the acoustic signal include changes in the amplitude of the speech envelope and shifted spectral peaks. Between-speaker variability can be due to several specific speaker characteristics, such as the length of the speaker’s vocal tract, speaker rate, and accent.