1. Overview
The physical attributes of a vocal/acoustic phenotype for any one species
or individual are shaped through the process of natural selection by an ecological environment that has biotic and abiotic components (e.g., Morton
1975, 1982;Wiley 1983; McCracken and Sheldon 1997; Bass 1998).The biotic
environment mainly includes the influences of other organisms, whereas
the abiotic environment includes the physical parameters (e.g., temperature, sound velocity of the transmission medium, geometry of reflective surfaces, composition of boundaries) that can affect acoustic transmission in
both the temporal and spatial domains. Here, we focus on the possible influences of the abiotic environment on the vocal communication signals of
aquatic vertebrates in part because there is a dearth of information and
studies for this group, unlike the case for terrestrial vertebrates and invertebrates (e.g., see Michelsen 1978; Wiley and Richards 1982; Gerhardt 1983;
Wiley 1983; Waser and Brown 1986; Bailey 1991; also see Chapter 5 by Ryan
and Kime). First, we provide a basic review of the physical attributes of
sound and the general principles governing the relationships between
underwater acoustic propagation and the physical environment, which can
also apply more generally to sound transmission in any medium. Next, we
discuss more realistic expressions of sound propagation in terms of two different environments, shallow water and deep water, and consider studies
that provide an empirical assessment of sound propagation for these two
environments as it impacts acoustic communication. We will focus on two
distantly related vertebrate groups, cetaceans and teleost fishes, which are
the foci of our own research programs and in some sense represent two
extremes relative to the abiotic influence of sound propagation on acoustic
signaling in an aquatic environment.
There are several textbooks that we recommend as bioacoustic primers.
Speaks’ (1992) Introduction to Sound provides a comprehensive treatment
of sound transmission in air, which is generally applicable to the principles
underlying sound propagation in any medium. The introductory chapters in
15
2
The Physical Acoustics of
Underwater Sound Communication
Andrew H. Bass and Christopher W. Clark
The physical attributes of a vocal/acoustic phenotype for any one species
or individual are shaped through the process of natural selection by an ecological environment that has biotic and abiotic components (e.g., Morton
1975, 1982;Wiley 1983; McCracken and Sheldon 1997; Bass 1998).The biotic
environment mainly includes the influences of other organisms, whereas
the abiotic environment includes the physical parameters (e.g., temperature, sound velocity of the transmission medium, geometry of reflective surfaces, composition of boundaries) that can affect acoustic transmission in
both the temporal and spatial domains. Here, we focus on the possible influences of the abiotic environment on the vocal communication signals of
aquatic vertebrates in part because there is a dearth of information and
studies for this group, unlike the case for terrestrial vertebrates and invertebrates (e.g., see Michelsen 1978; Wiley and Richards 1982; Gerhardt 1983;
Wiley 1983; Waser and Brown 1986; Bailey 1991; also see Chapter 5 by Ryan
and Kime). First, we provide a basic review of the physical attributes of
sound and the general principles governing the relationships between
underwater acoustic propagation and the physical environment, which can
also apply more generally to sound transmission in any medium. Next, we
discuss more realistic expressions of sound propagation in terms of two different environments, shallow water and deep water, and consider studies
that provide an empirical assessment of sound propagation for these two
environments as it impacts acoustic communication. We will focus on two
distantly related vertebrate groups, cetaceans and teleost fishes, which are
the foci of our own research programs and in some sense represent two
extremes relative to the abiotic influence of sound propagation on acoustic
signaling in an aquatic environment.
There are several textbooks that we recommend as bioacoustic primers.
Speaks’ (1992) Introduction to Sound provides a comprehensive treatment
of sound transmission in air, which is generally applicable to the principles
underlying sound propagation in any medium. The introductory chapters in
15
2
The Physical Acoustics of
Underwater Sound Communication
Andrew H. Bass and Christopher W. Clark