HomeMy WebLinkAbout11-20-2012 lord ph1 public commentMEETING AGEND A
DATE i ~- ITEM #
45d8 .co m
Acoustics Consulting
P . O . Box 140 6
San Luis Obisp o
California 9340 6
DAVID LORD,PH .D .
Principal Consultant
tel . 805 .704 .804 6
entail:dl(@45dB .corn
November 20, 201 2
SLO Brew Higuera Street Acoustical study :
Rooftop sound levels with six-foot wall on northwest sid e
Ambient sound levels at ground level are not affected by rooftop activity, as shown in th e
diagram .
The rooftop patio sound wall reduces rooftop sound levels by more than ten decibels, from 68 d B
to 55 dB toward ground level .
A ten decibel sound reduction is perceived subjectively as a halving of the rooftop activity soun d
level .
Ground level ambient sound level is around 62 dB, therefore, the sound coining from the rooftop
at less than 55 dB is inaudible, as it is below the ambient sound level .
The effectiveness of the rooftop sound barrier depends on blocking the line-of-sight from the
sound source to the sensitive receptor . This principle operates for distant residences as well .
Doubling the distance from the sound source to a receiver results in a 6 decibel drop in soun d
level.
If sound level is 55 dB at 20 feet distance, then sound level will be 49 dB at 40 feet distance fro m
the sound source .
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