Comparison of standard deviation of log-amplitude fluctuations for two frequency bands. σ_χ,lowfreq (dB) is bandpass filtered for 446–707 Hz, corresponding to the one-third octave frequency bands with center frequencies 500 Hz and 630 Hz. σ_χ,highfreq (dB) is bandpass filtered for 708–1122 Hz, corresponding to the one-third octave frequency bands with center frequencies 800 Hz and 1000 Hz.