Accoustics

Accoustics is a branch of Engineering that is concerned with how the sound
environment of a building.

Accoustics is how a building reacts to sound, how it absorbs and reflects
sound, and with reverberation qualities of the room.

Unfortunately, we deal with accoustics after the fact.  Little can be done
to improve existing accoustics.  You can only find out why you have
problems and try to deal with them.

Good hearing conditions depend on:
	a)  Adaquate loudness
	b)  Good distribtion of sound
	c)  Both proper blending and proper separation between sounds
	d)  A quiet environment

LOUDNESS

Sound must be loud enough to be heard.  This is not always easy.

--Sound tends to emanate from a source in spherical pattern.  An expanding
sound wave is covering a geometrically expanding area, so sound is subject
to the inverse square law.  

Intensity equal to inverse square of the distance.

For every doubling of distance, intensity will be 1/4.

--Sound is also subject to accoustic shadowing.

If a solid object is beween the source and the receiver, it will tend to
block some frequencies.  This is more pronounced with high frequencies.

A frequency will be blocked by objects proportional to its size.  The
higher the freq., the smaller object is required to block it.  Low
frequencies tend to wrap around small objects but are blocked by large ones.

--Different freq are affected differently by distance.
High freq. tend to be heard better by the human ear than low freq.
Therefore, even though inverse square AFFECTS highs and lows equally, be
tend to hear low intensity hghs easier than lows, and so low freqs fall
below the threshhold of hearing sooner than highs.

At a distance, you can only hear the highs.

©2000, Mick Alderson