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. 2013 May 7;8(5):e63728. doi: 10.1371/journal.pone.0063728

Figure 2. Qualitative comparison of speech loudness judgments with empirical predictions.

Figure 2

(A) Speech loudness as a function of intensity (level above auditory threshold). The solid line represents the best-fit curve to the psychophysical data within the range of typical speech SPLs, redrawn from Fletcher and Galt [20]. The dashed line shows the trend beyond typical speech levels. (B) The probability distribution function of SPLs in the speech database. The bimodal shape is due to the characteristically different amplitudes of sustained speech sounds (i.e., vowels and some consonants) and transient speech sounds (e.g., aspiration noise from consonants). (C) The CDF derived from the PDF in (B) is generally similar to the psychophysical function in (A).