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.