The definition of 'sound' evidently depends on whoever defines or 'interprets' it. The American Heritage Dictionary installed on my computer lists the following definitions first:
> sound (sound) n.
> 1.a. Vibrations transmitted through an elastic material or a solid,
> liquid, or gas, with frequencies in the approximate range of 20 to
> 20,000 hertz, capable of being detected by human organs of hearing.
> b. Transmitted vibrations of any frequency. c. The sensation
> stimulated in the organs of hearing by such vibrations in the air or
> other medium. d. Such sensations considered as a group.

Mary C.