Basic Concepts of Sound
In some ways, sound waves are much like electromagnetic or light waves.
In a homogeneous medium, they travel at a constant speed, c. (The speed
of sound in air is 343 m/s, or about 1 foot per millisecond, which is a
handy number to remember.) A uniform point source radiates spherical waves
whose amplitudes fall off inversely with distance. These waves are reflected
by smooth surfaces and scattered by rough surfaces. A surface
is "smooth" if the size of irregularities is small relative to
the wavelength, and "rough"
otherwise.
Sound waves are diffracted around intervening objects.
If the object is small relative to the wavelength, it has very little effect
-- the wave just passes around the object undisturbed. If the object is
large, a "sound shadow" appears behind the object and a significant
amount of energy is reflected back towards the source. If the object is
about the same size as a wavelength, things are complicated, and interesting
"diffraction patterns" appear.
On to Sine Waves
Up to Physics