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Posted by Gene E. Bloch on 04/25/06 22:05
On 4/24/2006, thanatoid posted this:
> Gene E. Bloch <spamfree@nobody.invalid> wrote in
> news:mn.c2cb7d64b505b446.1980@nobody.invalid:
>> In all fairness: the human auditory system is far more
>> clever, not to mention complicated, than you seem to
>> realize. I can tell where sounds are coming from pretty
>> much over the whole 4 pi steradians, as can most people. So
>> the x.1 or x.3 (cute) systems do provide a deeper
>> experience for at least some listeners.
>
> While I have NO idea what "4 pi steradians" means, I am well
> aware that 5.1 (NOT sure about 7.1) is AUDIBLY different (not
> superior, just different) from stereo let alone mono. IMO, some
> stuff sounds better in mono no matter what it is.
A steradian (from stere, solid, and radian, an angular unit, from
radius) is a unit of "solid angle". I guess I should add that pi is the
usual constant, 3.14159..., but I better not stop there, huh?
Solid angle is the three dimensional analog of angle. A regular angle
is a percentage of the circumference of a circle as marked out by an
arc on the circumference as seen form the center of the circle. Solid
angle is similarly the percentage of the area of a sphere marked out by
an area on the surface as seen from the center of the sphere. The area
can have any shape, unlike in the 2-D case.
If you recall the formula for the area of a circle, it is A = 4 pi
r-squared. Thus a circle where r = 1, called a unit sphere, has an area
of 4 pi, and the area of an arbitrary shape on the surface of a unit
sphere is its angle in steradians. Thus, 4 pi steradians means all
directions, up, down, left, right, forward, behind; so, it is the
entire world surrounding you.
While I'm ranting: Regular angles can be measured in radians, which are
the length of an arc on a unit circle, so a full circle has two pi
radians.
The exam will be Friday at 10:00 AM.
HTH,
Gino
--
Gene E. Bloch (Gino)
letters617blochg3251
(replace the numbers by "at" and "dotcom")
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