The best selling CD in New Zealand, aptly named, "A very silent night", is one you will never be able to hear. It has been recorded at a frequency only your pooch can listen to.

Released for charity by the "Society for the Prevention of Cruelty to Animals" (SPCA), this CD became an instant hit amongst dog owners in New Zealand. To date the $3.90 CD, which contains both, the instrumental (music only) and the vocal version (with words) of the song, has raised over 17,300 U.S. Dollars for the charity.

While dog owners love it, the reaction amongst the dogs has been a little mixed. The most extreme one has been by a dog that went a little crazy upon hearing the song and destroyed the radio. Most dogs however just seem to lie down and do nothing.

The success of the CD has encouraged the SPCA so much, that they are going to release the CD around the world, and it will soon be available to dogs in the U.S.A. and Australia.

What is Frequency?

Humans (and dogs) hear when sound waves hit the eardrum, causing the inner ear bones to vibrate. The number of vibrations per second is called frequency. Frequency is measured in Hertz (one Hz being one vibration). Humans have a 20 -20,000 Hz frequency range. They cannot hear anything beyond that. Dogs on the other hand have a much higher frequency range, from 40 to 60,000 Hz.