On 2008 Jan 14 , at 5:50 AM, STANLEY DOORE wrote:
Pianos make sound. Sound waves and frequencies (radio and TV) are
given in metric (mm, cm and m) as common practice for more than 100
years. So it seems logical to build pianos using metric units.
The frequencies of sound waves are not usually "given in ... mm, cm
and m". Those length units could be used to report the wavelength of a
wave and that would be quite correct. However, sound waves are NOT
USUALLY reported as such. Instead, sound waves are almost always
specified by their frequency (which is related to their pitch).
Frequency in metric is measured in hertz (Hz) and its multiples. (One
hertz equals one oscillation per second.)
However, many radio/TV waves are also specified by their frequency (in
hertz). While it is true that some of the lower frequency (and
therefore greater length) radio waves have been commonly specified by
their wavelength ("millimetre waves", "microwaves*", "3 m waves",
"quarter wave length antennas", etc.) by far, the commercial broadcast
bands are almost always referred to by frequency**.
So, Stanley's suggestion may be good if applied to frequencies in
hertz, but not in connection with wavelengths in millimetres etc.
Regards,
Bill Hooper
==================================
Additional comments, off the main subject but maybe interesting to some.
* I believe "microwaves" is a term used to describe radio waves of
wavelengths in the micrometre range, but I am not certain of that
fact. Does anyone know the wavelength used in common microwave ovens?
Such ovens all use the same frequency, I believe; namely, the
frequency which most efficiently transfers energy to the hydrogen-
oxygen bond in water and other molecules. That's why they heat the
water in a cup but not the cup.
**The AM radio band runs from about 550 kHz to 1600 kHz while the FM
band runs from 87.7 MHz to 107.9 MHz. That means the FM waves at the
SLOW end of the FM dial are oscillating about 55 times FASTER than the
FASTEST waves on the AM dial. (87.7 MHz is about 55 times 1600 kHz.)
For comparison, audible sound waves (those that can be heard by the
human ear) are in the
range from 20 Hz to 20 000 Hz (20 kHz). These are not sharply defined
because they depends on an individual's ears. I mysefl haven't been
able to hear above 15 kHz most of my life.
