Nasal Pressure and Sound Production in an Echolocating White Whale, Delphinapterus leucas
At the Jersey conference on Animal Sonar Systems in 1979 we gave strong evidence that dolphins produce sound in the nasal system rather than in the larynx as most mammals do (Ridgway et al. 1980). With electromyography (EMG), we studied the activity of laryngeal muscles and nasal muscles, making comparisons between the two groups of muscles during sound production. Certain muscles of the nasal system were active during all dolphin whistles and click trains while muscles of the larynx were active during respiration but not during sound production. Perhaps more importantly, we measured pressure in the nasal cavities and in the trachea adjacent to the larynx. During sound production, intranasal pressure increased markedly but intratracheal pressure remained unchanged. Subsequently, Amundin and Andersen (1983) replicated the EMG and pressure monitoring aspects of our study in Tursiops and Phocoena.
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