All Blue Whales in the Northern Hemisphere produce sounds with generally similar features. Common sound types include: long, constant frequency (CF) moans; long, frequency-modulated (FM) moans; and long, amplitude-modulated purrs. All such sounds typically have durations of 5-25 seconds with fundamentals below 25 Hz, and harmonics are sometimes emphasized. Various combinations of these basic sound types occur in deliberate, patterned sequences lasting many tens of minutes, and these sequences are repeated in bouts lasting up to many days.
In the Atlantic Ocean, Blue Whales make moans at a frequency range of 10 to 39 Hz, with dominant frequencies of 16 to 28 Hz. The illustration below, Figure 1, is a sound spectrogram of a 6.7-minute recording of a Blue Whale, made by Navy ocean-bottom surveillance microphones in the western North Atlantic.
To hear the recording, click on the spectrogram below. The sound you will hear is speeded up twenty times faster than normal speed, which also raises the pitch of the whale sounds by a factor of twenty. If this recording were played at normal speed, you would not be able to hear anything, because the frequencies at which they call are below the range humans can perceive.
Blue Whales in the Pacific Ocean produce trills ("A" calls) and moans ("B" calls) in the frequency range of 10 to 39 Hz, with dominant frequencies of 16 to 28 Hz. The sound spectrogram below, Figure 2, is of a Pacific Blue Whale recorded off the coast of California by underwater microphones towed by a Navy surveillance vessel. It shows a pattern of "A, "B", "B", "B" calls. Because of the loudness of the calls in this recording, the calls appear as harmonics at mutiples of the frequencies of the primary call.
To hear the recording, click on the spectrogram. The sound of the whale is so low it is barely audible to humans; the sound you will hear has been speeded up ten times, which raises the pitch three and a half octaves, to make it more clearly audible. The sound consists of four parts: first, a trill, or series of click-like sounds, followed by three repetitions of a moan like a foghorn.