3-3. Temporal variation in call rate and its contribution to the
soundscape
The call counts per hour, as presented in Figure 6A, were relatively
lower from 05:00 to 17:00 on December 10. The Pearson correlation
coefficient between the hourly call counts and sound pressure levels
over 54 hours showed a weak positive correlation (r = 0.40,p = 0.0029). Figure 6B represents the results of the correlation
analysis between the hourly call counts and spectrum levels at 1-Hz
intervals. High correlations were observed at 323, 652, and 2,809 Hz
frequencies within specific bandwidths. The peak at 323 Hz, which
closely resembles the 328 Hz peak in the median spectrum level of the
underwater soundscape, exhibited a strong positive correlation with a
coefficient of 0.9.