Fig. 3
From: Visualizing sound: counting wolves by using a spectral view of the chorus howling
Three wolves’ choral howls. Chorus howls of at least three different wolves (free-ranging) recorded during the howling survey in 2007. Spectrogram (a) and spectrum (b) (window length: 4026 samples) were computed by Seewave, an open source R project package dedicated to the sound analysis. Colours (from red to blue) represent amplitude degradation. See also Additional file 1 and Additional file 2 for analysis of wolves choruses with Seewave