Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Relation between amplitude differences between pairs of songs in a song bout (a, b, c), or between syllables within a song (d, e, f), and differences in maximum, peak and minimum frequency (louder minus softer). Regression lines are for illustration purposes only, as statistical tests were nonparametric.
