Elephant Call Types Database
Rumbles are the most frequently heard call type across both sexes and all ages of African savanna elephants, and may be easily distinguished from other call types by their very low frequencies and clear harmonic structure. Over 90% of the calls in our database are rumbles. A large number of specific stimuli evoke rumbling sounds and these are described in detail in the database which examines the behavioral contexts of calls. Rumbles originate in the larynx (source) and resonate (filter) through the pharyngeal pouch, the nasal passages of the skull and through the trunk. Rumbles can be produced with the mouth open and others with the mouth, apparently, closed. Open-mouthed calling is associated with the louder, more modulated rumbles.
Rumbles are highly variable, graded calls containing fundamental frequencies ranging between 8 and 34 Hz depending upon the caller’s age, size and excitement level, as well as the call context-type. Some rumbles are highly modulated, powerful sounds, others rise or fall in pitch, some rumble contours are flat, some undulating, and still others are jittery.
Rumbles range in duration from less than half a second to almost 12 seconds, and may be emitted as a soft fluttering whisper or an explosive throaty resonance with sound pressure levels up to 103 dB extrapolated to 5 meters from source. Very powerful rumbles tend to be both highly modulated and contain more noise. Bandwidths range from 38-1000 Hz with some of the variance being explained by the distance of the microphone from the source. Although there is considerable variation within age classes, the rumbles of older individuals are longer in duration and lower in frequency than those of younger individuals.
A long, unmodulated rumble by an adult female.
A relatively long, undulating rumble by a juvenile female.