Introduction to Acoustic Terminology and Signal Processing

Abstract

This chapter presents an introduction to acoustics and explains the basic quantities and concepts relevant to terrestrial and aquatic animal bioacoustics. Specific terminology that is introduced includes sound pressure, sound exposure, particle velocity, sound speed, longitudinal and transverse waves, frequency-modulation, amplitude-modulation, decibel, source level, near-field, far-field, frequency weighting, power spectral density, and one-third octave band level, amongst others. The chapter then introduces basic signal sampling and processing concepts such as sampling frequency, Nyquist frequency, aliasing, windowing, and Fourier transform. The chapter concludes with an introductory treatise of sound localization and tracking, including time difference of arrival and beamforming.

Intertidal Soundscapes of Hardened and Living Shorelines: A Case Study of Habitat Enhancement

“…The methods used to describe attenuation differences between the hardened and living shoreline sites found effects of distance from the speaker but not differences between sites (Figure 6). The cylindrical spreading model tended to overestimate transmission loss compared to what was measured, which could have been the result of the vegetation, the substrate, or a variety of other factors potentially influencing transmission loss at the sites (Erbe & Thomas, 2022; Miksis‐Olds & Miller, 2006; Rogers & Cox, 1988). The measurements may also have been influenced by heterogeneous, high‐amplitude, ambient sounds or micro‐scale differences in recorder position, leading to the variation in received levels detected even when the recorders were placed next to each other at the same distance from the speaker (Figure 6).…”

“…The model was tested for significance using the same methods as the diel sampling. A range of expected transmission loss values based on a cylindrical spreading model (TL = 10 log( r ) + 10 log( h ), where TL is transmission loss, r is the distance between the recorders and h is the average water depth of the recorders) was calculated for each distance for comparison (Erbe & Thomas, 2022; Miksis‐Olds & Miller, 2006; Rogers & Cox, 1988). When both recorders were placed 1 m from the speaker, the expected transmission loss between them was assumed to be 0 dB.…”

Sound production by the short‐beaked echidna (Tachyglossus aculeatus)

“…Vocalizations were identified aurally and visually from the spectrogram, and the duration, minimum frequency and maximum frequency (Table S1) were determined manually by drawing a sound selection box with Raven Pro. The other measurements in Table S1 were calculated by Raven Pro for each selection box (Charif et al., 2010; Erbe, Duncan, et al., 2022; McFadden et al., 2022; Schoeman et al., 2022).…”

What is a trait? Lessons from the human chin

“…displaced by the quantitative traits of geometric morphometrics, which are based on arrays of measured points ("landmarks") that can be studied using statistical and computational techniques (Bookstein, 1991;Mitteroecker & Schaefer, 2022). Similarly, animal vocalizations that have been described and compared qualitatively by the human ear for "calls" or "songs" can now be quantitatively analyzed and compared in terms of acoustic parameters that humans may be unable to discriminate (Erbe & Thomas, 2022). Operationalization need not always involve quantification and can also sometimes combine qualitative and quantitative aspects-for example, measuring the behavioral trait of aggressiveness in terms of rates of "aggressive" encounters.…”