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

Report No. 6945
BBN Systems and Technologies Corporation
N - The number of sources of a spedific type expected to be
found in area At. This includes only the sources that
are active at a given time.
SNC1 - The standard noise contribution rating for a specific
source based on the effective bandwidth level, Lsl.
SNC~ = Leq + 10 Log(Pe) +'lo ~ og (N) (24)
SNC2 - The standard noise contribution rating for a specific
source based on the maximum*1/3 octave band level, Ls2
5.2.2 The standardized exposure rating model
This model has been developed to provide a means of estimating the
potential impact of the noise energy of a given type of source operating in a
designated area on a single species found in that area. The model operates
using the following measures at the reference range from a specified source
(300 m):
The acoustic energy density of the noise, since the potential for
behavioral influence is considered to be proportional to the acoustic
energy level. This is approximately equal to the value of SNC1.
The population density of the species, since the encounter probability
is proportional to the number of animals present.
The amount of overlap between the output spectrum of a source and the
hearing sensitivity curve of a given species.
The hearing response is a broad filter which when matched to the output
spectrum of a source produces a higher loudness sensation than occurs when the
dominant frequency range of the source is outside of the maximum hearing
sensitivity region. As shown in Fig. 5.2, the model uses a measure of the
bandwidth of the overlap region together with a measure of the maximum
difference between the hearing threshold and the received level in the overlap
region.
where :
The SER Model is described by the equation:
SER = SNC1 + 10Log(Ds) + Lr3 - SS + 10Log(BWeff) dB (26
Ds = Density of the species in the model area (~/lan~)