Oceans of noise - Whale and Dolphin Conservation Society

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i.e. Equal pressure measurements differ by 26dB in air and in waterStage2. Adjusting for differences in acoustic impedance (_c) between air and water.⎛ I ⎞ ⎛ ( ρc)⎞Air10 log⎜ 10 log = 10log +I⎟ ≈ ⋅⎜Water( c)⎟⎝ ⎠ ⎝ ρWater ⎠( 3600) = dBAir36i.e. The difference between a SIL measured in water and SIL measured in air is:26 dB + 36dB= 62dBTherefore if a SIL is measured in air it has been proposed that its equivalent SIL underwater might beachieved by adding 62 dB, and, conversely if a SIL is measured in water, subtract 62dB from its valueto get its equivalent value in air.However, this may be a risky comparison because the mechanisms leading to damage in the earunderwater may be significantly different to those in the air.21
2.2. Types of sound sourceSounds can be transient (short duration sounds with obvious start and finish points) such as thoseproduced by explosive blasts or percussion piling, or continuous (such as drilling). Transient soundsare usually described by their peak level (the maximum amplitude measured in dB) with anaccompanying indication of how this varies in time. If a transient sound is impulsive (with a durationof less than 0.5 seconds) it is best described by its energy level. Continuous sounds and long durationtransient sounds are conventionally described by their mean square pressure.2.3. The propagation of underwater noiseSource path receiver model of soundWhen describing the propagation of underwater noise it is useful to apply a simplistic model to thisprocess. These models are based on the sonar equation and perhaps the simplest of these is the SourcePath 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), andambient 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 − TLWhere 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 theresult of spreading, absorption, scattering, reflection and rarefaction. Transmission loss can also beestimated by adding the effects of geometrical spreading (TL sp ), absorption (TL a ) and the transmissionloss anomaly (A). The transmission loss anomaly includes scattering loss and losses due to reflectionand rarefaction at boundary interfaces.TL= TLspreading + TLabsorption+AFor simplicity we'll only deal with spreading (TL sp ) and absorption loss (TL a ):TL = TL g+ TL a(1) TL sp - Spreading lossSpreading loss is a major component of transmission loss and is range (distance) dependent. Twoforms of spreading loss are common underwater (1) Spherical or Geometrical spreading loss (TL g ),and (2) Cylindrical spreading loss (TL cy ).22
Page 2: Oceans of Noise 2004A WDCS Science
Page 8 and 9: In the US, the deployment of Low Fr
Page 10 and 11: its propagation beyond those declar
Page 12 and 13: The best evidence for noise being f
Page 14 and 15: Box 1. Characteristics of sound / l
Page 16 and 17: Sound speed (c)The speed (c) of a w
Page 18 and 19: Box 2. The effects of temperature,
Page 20 and 21: 2.1.2. Measuring sound intensityIde
Page 24 and 25: Spherical or Geometrical spreading
Page 28 and 29: 5.0 145Tug pulling loaded barge 1.0
Page 30 and 31: The source used during 3-D surveys
Page 32 and 33: Machinery noisePropulsion machinery
Page 34 and 35: Man-made islands /caissonsFixed pla
Page 36 and 37: 12 3245Drill bit6Figure 3.4. Sound
Page 38 and 39: Transientnoise sourcesAircraftHelic
Page 40 and 41: Results from the aerial surveys con
Page 42 and 43: haemorrhaging in the inner ears and
Page 44 and 45: However they also noted that whales
Page 46 and 47: 4. The Use of Sound by CetaceansChr
Page 48 and 49: seems logical, therefore, that if t
Page 50 and 51: However, despite the reported low a
Page 52 and 53: Kamminga and Wiersma 1981;Akamatsu
Page 54 and 55: SongSocial callsShrieksSlaps0.03-80
Page 56 and 57: anthropogenic factors that make the
Page 58 and 59: 5.3 Longer-term impactsNoise is cle
Page 60 and 61: 5.4 Indirect impactsThe above impac
Page 62 and 63: decompression sickness (DCS) as see
Page 64 and 65: 6. Examples of regional and nationa
Page 66 and 67: 6.3 ASCOBANS and ACCOBAMSTwo region
Page 68 and 69: implications and the discussion sho
Page 70 and 71: 7.1. Consideration of Voluntary vs.
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acoustic measurements have been mad
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7.6. Methods of protectionComplianc
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7.6.1 Monitoring7.6.1.1 Visual, aco
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Delory et al. (2002) use Ambient No
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8. ReferencesAburto, A., Rountry, D
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Caldwell, M.C., Caldwell, D.K., and
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Engas, A., Lokkeborg, S., Ona, E. a
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IWC 2002b. Report of the Scientific
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McCauley, R.D. 1994. Seismic Survey
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Potter, J. and Delory, E. 2001. Noi
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Smolker, R.A., Mann, J. and Smuts,
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Watkins, W.A. 1981b. The activities
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ANNEX 1The Application of Marine Po
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an important factor. 13 The judgeme
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in the preparatory work of the LOSC
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practice by the UNEP Governing Coun
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protection and preservation of the
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than international rules, standards
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Four of the twelve regional seas tr
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seismic operations in the Protocol
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ConclusionAt the global level, only
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Art 209 LOSC focuses on both standa
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No State Party may impose condition
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coastal States”. This formulation
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If the IMO makes this determination
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estrictions to vessels operating in
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In the EEZ, in comparison to the te
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Appendix A - Some international ins
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Convention for the Protection of th
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Available at:http://www.unep.ch/sea
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BucharestConventionArticle XIPollut
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environment1. The Contracting Parti
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- that under Article III.8.c) of AC
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e) no sudden or repeated change in
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Ref: Nowacek et al. 2001.Location:
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Location: Arctic• Vocal behaviour
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• Vaquita surfacing duration and
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• 6% of small delphinids (n=264;
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Species type: Boto, Inia geoffrensi
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• Humpback whales appeared tolera
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• Behaviour interpreted as aggres
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• There was no evidence of minke
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• Northern right whales may be ap
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• Migrating gray whales disturbed
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to Ensenada De La Paz, Mexico. Aqua
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distribution of humpback whales, Me
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Richardson, C.R. Greene, C.I. Malme
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Zhou, K., Pilleri, G. and Li, Y. 19
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6. surveys for Cuvier’s beaked wh
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Oceans of noise - Whale and Dolphin Conservation Society

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