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

Report No. 6945
BBN Systems and Technologies Corporation
6.2 Recommendations
The modeling procedure developed in the study provides a means of ranking
source - species encounter situations using acoustic principles. While the
principles employed have been used in similar ways to predict human annoyance
by industrial noise, their application here to marine mammals has involved the
use of several untested assumptions. Moreover, it has been necessary to use
estimated and inferred values for many of the required model inputs where
'measured data are not presently available. When appropriate data become
available the procedures used in this study should be augmented and modified
where required.
While humans have been found to respond as energy detectors with a
fundamental stimulus integration time roughly equivalent to 8 hours, the
hypothesis built into the SER model of a 2 hour integration time for marine
mammals should be tested. This concept is useful for comparing different
types of sources on an energy equivalent basis, but other procedures can be
devised if it is found not to be appropriate for marine mammal psychoacoustics.
Possible testing procedures could be devised which will allow the
stimulus integration concept to be tested concurrently with testing for
adaptation using repeated controlled noise exposures.
Appropriate weighting factors should be investigated for use in the SER
modeling procedure which provide for the apparent increase in sensitivity of
certain marine mammals during special situations. This increase in
sensitivity occurs for the sudden onset of a new sound (startle effect), for a
sound that is increasing in level (indicating approach), and for sounds
indicating a known threat. The use of weighting factors in human response
modeling has been found to provide the flexibility needed to accommodate the
effects of special stimuli.
The accuracy and utility of the modeling procedures developed in this
study need testing with field data. Ideally this testing would initially
employ benchmark acoustic and biological data obtained from an area prior to
the onset of development. This would be followed up using data obtained
during the course of increasing industrial activity. The models would be run
and the results compared with observations of mammal reactions in the area as
the acoustic environment changed. The goal of this procedure is the
refinement of the present preliminary and largely untested models into a
marine mammal acoustic response model which would predict potentially
significant acoustic impact situations during the course of environmental
impact statement research and thereby allow time for assesment of the problem
and determination of mitigation procedures.