2.
Response
to
Comments
2.9
Individual
Responses
to
Comments
from
Organizations
“Sound
power”
and
“sound
pressure
or
level”
are
two
distinct
and
commonly
confused
characteristics
of
sound.
Both
share
the
same
unit
of
measure,
the
decibel
(dB),
and
the
term
“sound
level”
is
commonly
substituted
for
each.
Sound
power
is
the
acoustical
energy
emitted
by
the
sound
source,
and
is
an
absolute
value.
Unlike
sound
pressure,
“sound
power”
is
neither
affected
by
the
ambient
noise
environment
nor
distance
dependent.
Sound
power
belongs
strictly
to
the
sound
source,
and
is
not
affecting
by
its
location
or
setting.
Sound
pressure
or
sound
level
is
a
measurement
at
a
point
in
space
near
enough
the
source
to
hear
the
source.
Sound
pressure
or
sound
level
is
influenced
not
only
by
the
strength
of
the
source
(sound
power),
but
also
by
the
surroundings
and
the
distance
from
the
source
to
the
receiver.
Sound
pressure
or
level
is
what
the
human
ear
hears,
and
what
sound
meters
measure.
Sound
pressure
is
commonly
used
in
the
assessment
of
environmental
noise,
while
sound
power
is
used
as
a
specification
for
design
of
stationary
sources
such
as
turbines.
Sound
power
is
thus
not
a
useful
descriptor
for
the
purposes
of
environmental
noise
assessment.
Sound
power
can
be
thought
of
as
analogous
to
the
wattage
rating
of
a
light
bulb;
both
measure
a
fixed
amount
of
energy
at
the
source.
Sound
pressure
or
sound
level
would
then
correspond
to
the
level
of
brightness
in
a
particular
location;
both
can
be
measured
with
a
meter
at
a
specific
distance
from
the
source,
and
possible
blockages
between
the
source
and
receptor,
as
well
as
the
immediate
surroundings
at
the
receptor
influence
the
magnitude
of
each.
As
in
the
case
of
light,
where
brightness
is
more
than
a
matter
of
bulb
wattage
and
cannot
be
measured
by
bulb
wattage,
loudness
is
more
than
a
matter
of
sound
power
at
the
source,
and
cannot
be
measured
at
a
receptor
by
sound
power.
“Sound
power”
may
be
perceived
as
being
louder
than
sound
levels
since
sound
power
is
measured
at
the
source,
while
sound
levels
are
measured
at
receptors
some
distance
from
the
sound
source.
However,
“sound
power”
is
not
inherently
more
dangerous
than
sound
pressure
or
sound
levels.
The
discussion
on
page
4.J-2
of
the
Draft
EIR
is
general
introductory
information
on
noise
and
its
descriptors
and
is
not
intended
to
be
specific
to
the
City
of
Brisbane.
The
discussion
of
noise
specific
to
the
City
of
Brisbane
and
its
environs
is
presented
in
Section
4.J-2
,
Environmental
Setting,
of
the
Draft
EIR
beginning
on
page
4.J-5.
The
unique
environment
of
the
City
of
Brisbane
is
not
that
it
amplifies
sound,
but
rather
that
it
is
an
efficient
transmitter
of
sound.
The
slope
of
the
valley
means
that
homes,
like
seats
in
an
amphitheater,
have
a
“good
view”
of
noise
sources.
This
means
that
noise
will
propagate
more
efficiently
to
the
receptor
(with
less
loss)
than
in
a
typical
flat
community
because
buildings
are
less
likely
to
intercept
the
line-of-sight
of
the
receptor
to
a
noise
source.
As
the
noise
Brisbane
Baylands
Final
EIR
2.9.3-95
May
2015