Owner's Manual
Table Of Contents
•
Wind
-
Wind
gives
the
illusion
that
a
sound
is
coming
from
a
different
direction
than
it
really
is.
This
creates
a
resultant
propagation
vector
(see
diag.
1
).
When
sound
propagates
with
the
wind
it
tends
to
refract
downward,
and
against
the
wind
refract
upwards
(see
diag.
2),
(*refraction
is
the
term
used
to
describe
the
bending
of
sound)
.
CROSS
WIND
CROSS
WIND
I
i I
·:
.....
. : I
:•-.
1
:
~ ~
I
l,
::
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',J.! 1 I I
1 1 1 j
PROPAGATiqN
~
VECTOR
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1
CROSS
WIND
----~---------.·--------~
-----
•Temperature-
Temperature
differences
also
have
a
small
effect
on
sound
propagation.
Hot
air
is
less
dense
than
cold.
Sound
travels
faster
in
a
less
dense
medium
and
therefore
speeds
up
as
air
gets
warmer,
and
slows
down
as
air
gets
cooler.
The
result
is
the
refraction
of
sound.
For
example
this
may
manifest
itself
as
sound
propagates
over
a
cool
body
of
water
on
a
hot
day.
The
sound
will
tend
to
"bounce"
along
the
surface
of
the
lake
and
travel
a
lot
further
than
the
Inverse
Square
Law
may
dictate
(see
diags.
3 &
4).
SOUND
OUTDOORS
From
the
speakers
to
our
ears
-
Since
you
usually
want
a
target
background
SPL
of
about
70dB
-
80dB
to
your
listeners,
keep
in
mind
the
Inverse
Square
Law,
which
states
that
in
a
free
field
with
no
walls,
floor,
or
ceiling,
the
intensity
of
sound
decreases
with
the
square
of
the
distance.
For
example
when
you
double
the
distance
between
the
speaker
and
your
listener's
ear,
the
SPL
decreases
by
6dB
(i.e.
If
a
speaker's
output
is
1
OOdB
SPLat
10
feet
away,
at
20
feet
away
the
SPL
is
decreased
to
94dB.)
Don't
forget,
a 1
OdB
drop
will
sound
"half
as
loud".
/
-----
-............
---
·
--
--'
'-
COLD
AIR
~''
,,
,r
~~
~,
WATER
•