A NEW BIOPHYSICAL METHOD TO DETERMINE THE GAIN OF THE ACOUSTIC TRACHEA IN BUSH-CRICKETS

A method is described for measuring the gain (i.e., the change of ampl itude and phase angle) for sounds that propagate to the internal surfa ce of the tympana in ears working as pressure difference receivers. Th e gain of the acoustic trachea has been measured in two similarly size d and closely related species of bushcrickets, in which the acoustic s piracles and tracheae differ markedly in size. The amplitude part of t he gain is much larger in the species with the larger acoustic spiracl e, whereas the phase part is very similar in the two species. The meth od is compared with other methods, which in the past have been used fo r estimating the gain of sound pathways inside animal bodies.