Peeps

From Samuel Saunders [951009:0051 EDT]

At first I started to let the point go, since it is not really related to
PCT or this thread, but Bill Powers suggested that chicks may be producing
vocalizations which are "outside the range of human hearing". While I can
not say for sure that chicks produce no vocalizations outside the range of
human hearing, I am certain that neither chicks nor adult chickens hear
anything outside the range of normal human hearing. My work on behavioral
audiometry in normal hearing adult chickens (Saunders and Salvi (1993),
Journal of the Acoustical Society of America, 94, 83-90) indicates that
the frequency range of normal hearing for adult chickens is completely
included in the range of normal human hearing, and throughout this range
the sensitivity of the chicken is less than that of the human (although not
nearly so much as had been previously suggest by electrophysiological
measures of hearing in chickens). The behavioral data are quite
consistent with thresholds of the most sensitive single units in chicken
cochlear ganglion (Salvi, Saunders, Powers, and Boettcher (1992) Journal of
Comparative Physiology A, 170, 227-241, replotted in figure 4 of Saunders
and Salvi). In my JASA paper, I replot data from Gray and Rubel for 0-day
and 4-day chicks along with our adult chicken data in a figure (3) which
suggests that chick hearing improves for some time after hatching, and that
the improvement is both in sensitivity and in increasing upper frequency
cutoff of hearing.

The point of this is that it is highly unlikely that sound outside the
range of human hearing could be used in any control loop by either chicks
or adult chickens.

//----------------------------------------------------------------------------
//Samuel Spence Saunders,Ph.D.