ger
Date: Wed Mar 16, 2011 4:14 pm ((PDT))
Dan,
Can you upload the pdf to the files area. The pdf that I downloaded from th=
e web doesn't match your page numbers.
i.e., your second quote is on page 14 rather than 26
Thank you,
Wil Hershberger
Nature Images and Sounds, LLC
Hedgesville, WV
The Songs of Insects
My Blog
On Mar 16, 2011, at 6:59 PM, Dan Dugan wrote:
> There is some good terminology in the National Park Service's Soundscape =
Plan and Environmental Assessment for Zion National Park, page 25:
>
> "deviation from natural ambient can be used to identify reductions in lis=
tening area and alerting distance. Reduction in listening area quantifies t=
he loss of hearing ability to humans and animals as a result of an increase=
in ambient noise level. Under natural ambient conditions a sound is audibl=
e within a certain area around a visitor or animal. If the ambient level is=
increased due to a noise event, the area in which the sound is audible dec=
reases."
>
> and on p. 26:
>
> For example, under natural ambient conditions, an owl perched in a tree m=
ay be able to hear a mouse scurrying through the brush anywhere within an a=
rea of 100-square-meters of the perch. If a noise event increases the ambie=
nt level by 3 decibels (dBA), the area in which the owl can hear a mouse wo=
uld decrease by 50 percent to approximately 50-square-meters.
> Reduction in alerting distance is closely related to reduction in listeni=
ng area. The residual alerting distance is equal to the square root of the =
residual listening area. Instead of addressing losses in terms of an area, =
reduction in alerting distance expresses the reduction as a linear distance=
from a source. For example, under natural ambient conditions, a canyoneer =
may be alerted to the sound of a flash flood at a distance of 1-mile. If a =
noise such as an aircraft overflight increases the ambient level by 6 dBA, =
the distance at which the flood could be detected would decrease by 50 perc=
ent to approximately 1=E2=81=842-mile or 2,640-feet.
> Visitors and wildlife are impacted by their failure to hear natural sound=
s that would have been audible in the absence of noise: a bird misses the s=
ound of a worm, a mouse misses the footfall of a coyote, a visitor misses t=
he sound of a distant waterfall. Reductions in listening area and alerting =
distance capture these types of impacts.
>
> BTW the geometry is incorrect in Fig. 4 on p. 26.
>
> -Dan
>
>
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