"A Day In The Life," by the Beatles

Any sound repeated regularly between 1 and 15 pulsations per seconds is perceived as rhythm. When those impulses repeat more frequently than 15 times per second, they are actually perceived as a pitch!  Frequency is measured in Hertz, determined by the number of distinct sounds, or cycles each sound wave completes, within a single second. Musicians use the term pitch to describe how low or high a frequency sounds (Madsen & Madsen, 1997).

"[A Day In The Life] being the last song on the album, The Beatles found an interesting way to close it out. After the final note, Lennon had producer George Martin dub in a high pitched tone, which most humans can't hear, but drives dogs crazy. This was followed by a loop of incomprehensible studio noise, along with Paul McCartney saying "Never could see any other way," spliced together. It was put there so vinyl copies would play this continuously in the run-out groove, sounding like something went horribly wrong with the record. Kids, ask your parents about vinyl." -Annoymous comment on http://www.songfacts.com/detail.php?id=129

The 15 kHz "dog whistle" is limited by sound recording and reproduction limitations. Humans can hear up to 20kHz, but lose that range with age and ear damage. Sounds above 10kHz normally must be cranked out at a high volume, or decibel level, for most humans to perceive the sound. Not only are dogs able to hear these frequencies at lesser volumes, they can actually hear up to 45kHz, well above our human threshold of hearing. (http://www.eeggs.com/items/38179.html)


Madsen, Charles H. & Madsen, Clifford K. (1997). experimental research in music. Raleigh, NC: Contemporary Publishing Company of Raleigh, Inc.