In the Sound function section of the Turbo C Version 2.0 Reference Guide 1988 I found the following comment.
/* Emits a 7-Hz tone for 10 seconds. True story: 7 Hz is the resonant frequency of a chicken's skull cavity. This was determined empirically in Australia, where a new factory generating 7-Hz tones was located too close to a chicken ranch: When the factory started up, all the chickens died. Your PC may not be able to emit a 7-Hz tone. */
Is this story true?