Fig. 1.
Power spectra of the sound used in this study. A: the
averaged power spectrum calculated from the entire 200-s period of the
recorded sound source signal using a CF-5220 fast Fourier transform
(FFT) analyzer (Ono Sokki, Tokyo, Japan). It contains a
significant amount of high-frequency components above the audible
range. B: the averaged power spectra of the sounds
reproduced by the bi-channel sound presentation system (see text) in
different conditions. The power was calculated from the signal actually
recorded at the subject's head position using a B&K 4135 microphone
(Brüel and Kjær, Nærum, Denmark). The top,
middle, and bottom panels represent full-range
sound (FRS), high-cut sound (HCS), and low-cut sound (LCS),
respectively. The power spectrum of FRS is essentially identical to the
spectrum of the source and contains both a low-frequency component
(LFC) (i.e., the one used in the HCS condition) and a high-frequency
component (HFC) (in the LCS condition).