Sound and Techniques in Sound Analysis
Sakis Drosopoulos, Michael F. Claridge · 2005
Introduction ................................................................................................................................... 11 Sound Properties ........................................................................................................................... 12 Frequency and Wavelength ..................................................................................................... 12 Sound Propagation Properties: Attenuation, Near Field Effects and Distortion .................... 13 Substrate Vibrations ................................................................................................................. 15 Signal Structure and Terminology .......................................................................................... 15 Sound Acquisition ........................................................................................................................ 15 Microphones, Pick-Up Patterns and Properties ....................................................................... 16 Omnidirectional Microphones ............................................................................................ 17 The Cardioid Family ........................................................................................................... 17 Hypercardioid and Supercardioid ....................................................................................... 19 Ultradirectional Microphones ............................................................................................. 19 Parabolas ............................................................................................................................. 19 Other Microphone Properties, Impedance, Sensitivity and Self Noise Level ................... 20 Sound Recorders ...................................................................................................................... 20 Digital Audio Tape ............................................................................................................. 21 MiniDisc and Solid State Recorders ................................................................................... 21 Laptop Recording ................................................................................................................ 22 Techniques for Sound Analysis .................................................................................................... 22 Digital Representation of Sound ............................................................................................. 22 Sampling Rate ..................................................................................................................... 23 Sample Size (Amplitude Resolution) ................................................................................. 24 Storage Requirements ......................................................................................................... 25 Spectrum Analysis ................................................................................................................... 25 Time-Domain and Frequency-Domain Representations of Sound .................................... 25 Spectral Analysis of Time-Varying Signals: Spectrograms and STFT Analysis .............. 26 Spectral Imperfections and Filtering Functions ................................................................. 31 Conclusion: Present and Future ................................................................................................... 32 Appendix ....................................................................................................................................... 32 The science dealing with the methods of generation, reception and propagation of sound is called acoustics. The branch dealing with sounds produced by animals is called bioacoustics. The songs of insects are among the major sources of biological noise in the environment. Studying insect sounds sometimes requires specialised instruments and techniques for the acquisition and analysis of the signals (Burbidge et al., 1997; Bradbury and Vehrenkamp, 1998). The aim of this chapter is to highlight some sound properties, associated with insect signal production, transmission and detection as well as some of the instrumentation and methodology used for acoustic analysis.