Underwater Acoustics: Noise and the Effects on Marine Mammals A Pocket Handbook 3rd Edition Compiled by Christine Erbe www.jasco.com [email protected] 2101 – 4464 Markham St. 301 – 32 Troop Ave. Victoria, British Columbia Dartmouth, Nova Scotia V8Z 7X8 Canada B3B 1Z1 Canada Tel: +1.250.483.3300 Tel: +1.902.405.3336 Fax: +1.250.483.3301 Fax: +1.902.405.3337 [email protected] [email protected] Brisbane Technology Park The Roundel, St Clair’s Farm 1 Clunies Ross Court Wickham Road PO Box 4037, Eight Mile Plains Droxford, Hampshire QLD 4113 Australia SO32 3PW United Kingdom Tel: +61.7.3853.5218 Fax: +61.7.3853.5211 Tel/Fax: +44.1489.878439 [email protected] [email protected] Airgun ..................................................................................................... 17 Part A: Fundamentals of Underwater Acoustics ............... 1 Explosions .............................................................................................. 18 Units ......................................................................................................... 1 Pile Driving ............................................................................................. 19 Multiplier Prefixes .................................................................................... 1 3. Sound Propagation ................................................................ 21 1. Terminology ............................................................................ 2 a. Overview .................................................................................................. 21 Sound ....................................................................................................... 2 Wave Equation ....................................................................................... 21 Frequency................................................................................................. 2 Harmonic Solution .................................................................................. 21 Harmonics ................................................................................................ 2 Helmholtz Equation ................................................................................ 21 Wavelength .............................................................................................. 2 Solutions to the Helmholtz Equation ...................................................... 22 Speed ....................................................................................................... 2 b. Sonar Equation ......................................................................................... 22 Particle Velocity:....................................................................................... 3 One-way Sonar Equation ........................................................................ 23 Pressure ................................................................................................... 3 Two-way Sonar Equation ........................................................................ 23 Acoustic Impedance ................................................................................. 3 Transmission Loss ................................................................................... 23 Acoustic Energy ........................................................................................ 4 Geometric Spreading .............................................................................. 24 Acoustic Intensity ..................................................................................... 4 Molecular Relaxation (Absorption) Loss ................................................. 25 Acoustic Power ......................................................................................... 4 Reverberation ........................................................................................ 26 Decibel ..................................................................................................... 4 c. RAY Propagation ....................................................................................... 26 Levels in Air vs. Water .............................................................................. 5 Reflection ............................................................................................... 26 Some dB Mathematics ............................................................................. 5 Refraction ............................................................................................... 26 Peak Pressure ........................................................................................... 5 Snell’s Law .............................................................................................. 26 RMS Pressure ........................................................................................... 6 Sound Speed Profiles .............................................................................. 27 Source Level ............................................................................................ 6 SOFAR Channel ....................................................................................... 27 Sound Exposure Level............................................................................... 6 Convergence Zone .................................................................................. 28 Pulse Length ............................................................................................. 7 Shadow Zone .......................................................................................... 28 Duty Cycle ................................................................................................ 7 Lloyd Mirror Effect ................................................................................. 29 Fourier Transform .................................................................................... 7 4. Sound Receivers .................................................................... 29 Power Spectrum Density .......................................................................... 8 a. Transducers .............................................................................................. 29 Frequency Bands ...................................................................................... 8 Hydrophones .......................................................................................... 29 Octave Bands: .......................................................................................... 8 Sensitivity ............................................................................................... 29 1/3 Octave Bands: .................................................................................... 8 Projectors ............................................................................................... 30 Percentile Levels..................................................................................... 10 Near Field (Fresnel Zone) ....................................................................... 30 2. Sound Sources ....................................................................... 11 Far Field (Fraunhofer Zone) .................................................................... 30 a. Natural Sound Sources ............................................................................. 11 Directivity Pattern .................................................................................. 31 Ambient Noise Spectra (“Wenz Curves”)................................................ 11 Beamforming .......................................................................................... 31 Beaufort Scale ........................................................................................ 13 Gain ........................................................................................................ 31 b. Anthropogenic Sound Sources ................................................................. 14 c. Data Acquisition (DAQ) Boards ................................................................. 32 Ship Noise............................................................................................... 14 Resolution .............................................................................................. 32 Doppler Shift .......................................................................................... 15 Dynamic Range ....................................................................................... 33 Cavitation ............................................................................................... 15 Seismic Exploration ................................................................................ 16 Part B: The Effects of Noise on Marine Mammals ........... 33 (c) JASCO Applied Sciences i ii (c) JASCO Applied Sciences 5. Marine Mammals of the World ............................................. 33 Order CETACEA ............................................................................................ 33 Suborder ODONTOCETI .......................................................................... 33 Suborder MYSTICETI ............................................................................... 40 Order CARNIVORA ........................................................................................ 41 Suborder PINNIPEDIA ............................................................................. 41 Order SIRENIA .............................................................................................. 44 6. Marine Mammal