Qualities and drawbacks of radiotransmitted vocalizations of monkeys through laryngophones: New perspectives in analysis

Abstract

Radiotransmitted (RT) calls of monkeys equipped with laryngeal micro-transmitters are compared with those recorded by an external microphone (AT). Sharp attenuation of background noise and echoes results in better sonograms with RT than AT sounds. Sensitive detection of unvoiced calls or phonatory noises leads to knowledge of the motivational state of the animals and the mechanisms of their vocal production. However, the laryngophone acts as a low pass filter which limits RT spectra below 3 kHz. Constant distance and orientation between sound source and microphone permit us to get absolute (low-pitched call) or relative (high-pitched call) intensity measurements. Their generalization should be possible with the use of a specific weighting filter which would reconstitute the original energy of calls. The system has interesting applications in behavioral and ecological studies. © 1983 S. Karger AG, Basel.