Vocal tract filtering and the "coo" of doves.
Ring doves (Streptopelia risoria) produce a "coo" vocalization that is essentially a pure-tone sound at a frequency of about 600 Hz and with a duration of about 1.5 s. While making this vocalization, the dove inflates the upper part of its esophagus to form a thin-walled sac structure that radiates sound to the surroundings. It is a reasonable assumption that the combined influence of the trachea, glottis and inflated upper esophagus acts as an effective band-pass filter to eliminate higher harmonics generated by the vibrating syringeal valve. Calculations reported here indicate that this is indeed the case. The tracheal tube, terminated by a glottal constriction, is the initial resonant structure, and subsequent resonant filtering takes place through the action of the inflated esophageal sac. The inflated esophagus proves to be a more efficient sound radiating mechanism than an open beak. The action of this sac is only moderately affected by the degree of inflation, although an uninflated esophagus is inactive as a sound radiator. These conclusions are supported by measurements and observations that have been reported in a companion paper.
Fletcher
Neville H
NH
Research School of Physical Sciences and Engineering, Australian National University, Canberra 0200, Australia. neville.fletcher@anu.edu.au
Riede
Tobias
T
Beckers
Gabriël J L
GJ
Suthers
Roderick A
RA
D000403:Airway Resistance / Q000502:physiology; D000818:Animals; D010856:Columbidae / Q000502:physiology*; D004947:Esophagus / Q000502:physiology*; D005931:Glottis / Q000502:physiology*; D013018:Sound Spectrography; D014132:Trachea / Q000502:physiology*; D014828:Vocalization, Animal / Q000502:physiology*