Oceans of noise - Whale and Dolphin Conservation Society

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i.e. Equal pressure measurements differ by 26dB in air and in water Stage2. Adjusting for differences in acoustic impedance (_c) between air and water. ⎛ I ⎞ ⎛ ( ρc) ⎞ Air 10 log ⎜ 10 log = 10log + I ⎟ ≈ ⋅ ⎜ Water ( c) ⎟ ⎝ ⎠ ⎝ ρ Water ⎠ 21 ( 3600) = dB Air 36 i.e. The difference between a SIL measured in water and SIL measured in air is: 26 dB + 36dB = 62dB Therefore if a SIL is measured in air it has been proposed that its equivalent SIL underwater might be achieved by adding 62 dB, and, conversely if a SIL is measured in water, subtract 62dB from its value to get its equivalent value in air. However, this may be a risky comparison because the mechanisms leading to damage in the ear underwater may be significantly different to those in the air.
2.2. Types of sound source Sounds can be transient (short duration sounds with obvious start and finish points) such as those produced by explosive blasts or percussion piling, or continuous (such as drilling). Transient sounds are usually described by their peak level (the maximum amplitude measured in dB) with an accompanying indication of how this varies in time. If a transient sound is impulsive (with a duration of less than 0.5 seconds) it is best described by its energy level. Continuous sounds and long duration transient sounds are conventionally described by their mean square pressure. 2.3. The propagation of underwater noise Source path receiver model of sound When describing the propagation of underwater noise it is useful to apply a simplistic model to this process. These models are based on the sonar equation and perhaps the simplest of these is the Source Path Receiver Model. The basic parameters of this model are: (1) Source: the noise source, e.g. ship, sonar etc. Parameter of interest = source level (SL) (2) Path or medium: the water column. Parameters of interest include transmission loss (TL), and ambient noise level (NL) (3) Receiver: e.g. whale, hydrophone etc. Parameters of interest include signal to noise ratio (SNR), received sound intensity level (RL) and detection threshold (DT). A simple model of sound propagation is: RL = SL − TL Where RL is the received level, SL is the source level and TL is the transmission loss. Transmission Loss (TL) Transmission loss is the decrease in intensity of a sound as it propagates through a medium, and is the result of spreading, absorption, scattering, reflection and rarefaction. Transmission loss can also be estimated by adding the effects of geometrical spreading (TLsp), absorption (TLa) and the transmission loss anomaly (A). The transmission loss anomaly includes scattering loss and losses due to reflection and rarefaction at boundary interfaces. TL = TLspreading + TLabsorption + For simplicity we'll only deal with spreading (TLsp) and absorption loss (TLa): TL TL TL + = g (1) TLsp - Spreading loss a A Spreading loss is a major component of transmission loss and is range (distance) dependent. Two forms of spreading loss are common underwater (1) Spherical or Geometrical spreading loss (TLg), and (2) Cylindrical spreading loss (TLcy). 22
Page 1 and 2: Oceans of noise A WDCS Science repo
Page 3 and 4: Contents Author biographies 4 Prefa
Page 5 and 6: Author biographies Sarah Dolman Sar
Page 7 and 8: Preface Over the course of the last
Page 9 and 10: some thoughts on the mitigation and
Page 11 and 12: 1. Introduction Lindy Weilgart The
Page 13 and 14: 2. The physics of underwater sound
Page 15 and 16: Box 1. Characteristics of sound / l
Page 17 and 18: Box 2. The effects of temperature,
Page 19 and 20: Intensity The intensity of a sound
Page 21: For water, pref = 1µPa rms, _ = 1x
Page 25 and 26: Cylindrical spreading loss Cylindri
Page 27 and 28: Rain - - - - - - - - - 100-500 - Bi
Page 29 and 30: Energy source (Air gun array) 28 Se
Page 31 and 32: driving and pipe-laying (installati
Page 33 and 34: produced as the bubble collapses an
Page 35 and 36: and broadband noise sources decayed
Page 37 and 38: cetaceans to high levels of acousti
Page 39 and 40: Navigation (transponders) 38 7-60 1
Page 41 and 42: SONAR TYPE FREQUENCY RANGE AV. SOUR
Page 43 and 44: them from approaching fish farm cag
Page 45 and 46: 3.11. Research 3.11.1. Controlled E
Page 47 and 48: frequencies). These sound channels
Page 49 and 50: 4.3.6. Danger avoidance Many verteb
Page 51 and 52: Table 4.1. Summary of sound frequen
Page 53 and 54: Table 4.2. Summary of sound frequen
Page 55 and 56: 5. Noise as a problem for cetaceans
Page 57 and 58: Increased vulnerability to disease
Page 59 and 60: levels exceed the ear’s tolerance
Page 61 and 62: 5.6 A New Concern: Is noise causing
Page 63 and 64: stranding incident suggests that th
Page 65 and 66: The only cetaceans listed in Annex
Page 67 and 68: 6.4 The US Marine Mammal Protection
Page 69 and 70: 7. Solutions - mitigation and manag
Page 71 and 72: 2. More targeted studies into each
Page 73 and 74:
Noise pollution also needs to be co
Page 75 and 76:
ange. Therefore prey must be closer
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identification of images collected.
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Pierson et al. (1998) indicated a m
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Baur, D.C., M.J. Bean, M.L. Gosline
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Cummings, W.C., Thompson, P.O. and
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Gedamke, J., Costa, D., Dunstan, A.
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Lagadere, J.P. 1982. Effects of noi
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National Research Council. 2000. Ma
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Sayigh, L.S., Tyack, P.L., Wells, R
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Todd, S., Lien, J. and Verhulst, A.
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December 1989, Pacific Grove, Calif
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consider just the definition of pol
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This evidence therefore suggests th
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jurisdiction (“the UNEP Conclusio
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Designation of Particularly Sensiti
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inter alia, internal waters, the te
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ief framework provision on pollutio
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definitions are located in the anne
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Questions arise as to the identity
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opportunity for, or a hurdle to, ad
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145 LOSC in respect of polymetallic
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Seabed Authority) has been establis
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One possibility is the adoption by
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Identification and Designation of P
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Provisions on Ships’ Routeing to
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4. Conclusion This paper has analys
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Instruments adopted under Bonn Conv
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Appendix B - Treaties underlying re
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Appendix C - Selected provisions of
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abate, combat pollution of the Medi
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Annex 2. Guidelines for commercial
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1. Any commercial cetacean-watching
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Annex 3. Documented examples of cet
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Location: Sarasota, Florida, USA Pr
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Beluga whales, Delphinapterus leuca
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These results may indicate habituat
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Location: Northwest Atlantic Northe
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The dolphins started to display eva
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Boats that approached within 30m or
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Location: Hawaii On rare occasions
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Location: Beaufort Sea Aversion beh
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Location: Mexico Gray whale vocal b
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If boats changed their speed or cou
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Corkeron, P.J. 1990. Aspects of the
Page 163 and 164:
Kibal’chich, A.A., Dzhamanov, G.A
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ates of fin whales, Balaenoptera ph
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Annex 4. A note of the Recommendati
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4. the inclusion of anthropogenic n
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