Analysis and Ranking of the Acoustic Disturbance Potential of ...

Report No. 6945
I
BBN Systems and Technologies Corporation
TABLE 3.4
CULTURAL AND RECREAT IOllAL SOURCES
Source Type Darinont BY, Hz Wax 1/3 Oct,Hz Teuq!oral Time Source Level Data
fain fut Lsl,dB freq. Ls2,dB Pattern Ratio )Icas/Est, Referme
24' Outdrive, 2-80HP (20kt) (1) moving 40 16000b 167 500 156 Fluct. 0.L W Maln et 01. 1981
16' Zodiac, ZOHP (20kt) (1) mving 3150 10000 157 6300 152 Fluct. 0.& W Y
13' Uhaler, 20HP (20kt) (1) mving 630 6000 159 4000 153 Fluct. 0.L W Y
Smmchinc(16Mhr)(2) mving 250 2500 130 1600 124 Fluct. O.& E Hollidayetal.1980
Helicopter uanrrcp on ice (2) Local 63 1600 139 160 131 Contin. 1 E dennring and Uhi te 1984
Shotgm, 10ga (3) loco l 80 3150 172 500 162 lnpulse 0.005 w BEN Archives.
Notes:
b Bandwidth limited by available data
(1) Undcrwter mound
(2) Signatures obtained in wter uwkr ice cover
(3) Airbom soud
source level of 167 dB represents the upper range of source levels for most
recreational sources. This level is comparable to that produced by a 35 m
( 110 ft) twin-screw diesel vessel as shown in Table 3.3A. When several
vessels of this type are operating in close proximity the cumulative noise
level can reach values similar to those that would be produced by a medium
sized ship.
Example spectra for several of the more popular airborne sound sources
are shown in Fig. 3.18. Note that these are radiated noise spectra for a
range of 150 m, not source level spectra. The snowmobile spectrum is
reresentative of older models and was obtained during acceleration of the
machine while running at about 40 km/hr (25 mph). The spectrum for the 10
gauge shotgun shows peak 1/3 octave band levels. Since this is a highly
sporadic and impulsive source it is difficult to estimate a representative
time fraction to obtain an equivalent level. If a pressure pulse time
constant of 2 msec and a shot repetition rate of l/hr is assumed, the Leq for
the shotgun is est'imated to be about 60 dB less than the spectrum levels shown
in Fig. 3.18. The longer duration signal from the aircraft flyover thus is
one of loudest recreational source signah.