Strategies for weighting Strategies for weighting exposure in the exposure in the

development of acoustic development of acoustic criteria for marine criteria for marine

mammalsmammalsby the by the Noise Exposure Criteria GroupNoise Exposure Criteria Group

Presented to the 150th Meeting of the Acoustical Presented to the 150th Meeting of the Acoustical Society of AmericaSociety of America

17–21 October 2005, Minneapolis, MN 17–21 October 2005, Minneapolis, MN

Noise Exposure Criteria Noise Exposure Criteria GroupGroup (Authors) (Authors)

Ann BowlesAnn Bowles

Roger GentryRoger Gentry

William EllisonWilliam Ellison

James FinneranJames Finneran

Charles GreeneCharles Greene

David KastakDavid Kastak

Darlene KettenDarlene Ketten

James MillerPaul NachtigallW. John RichardsonBrandon Southall*Jeanette ThomasPeter Tyack

Former ContributorsWhitlow AuSam Ridgway* (ret)Ron Schusterman (ret)

*Note that Brandon Southall was left off the author list in the program. An erratum willbe published in the Journal and author list will be corrected online.

NMFS Charge to the NMFS Charge to the Noise Exposure Criteria Noise Exposure Criteria

GroupGroupDevelop science-based criteria for the onset of auditory injury and behavioral disruption from

noise exposure.

•It became clear that we needed to emphasize some frequencies and deemphasize others

•It would be best if each species had their own weighting functions for injury and behavior.

•But we don’t have the data to support the specification of these weighting functions.

•While these data are being collected, we need interim weighting functions.

20

40

60

80

100

120

140

160

10 100 1000 10000 100000 1000000

Frequency (Hz)

dB (r

e: 1

uPa)

Low-freq. Cetacean (estimated)Pinniped (air)Pinniped (water)Mid-freq. CetaceanHigh-freq. Cetacean

Marine Mammal GroupsMarine Mammal Groups: Taxa were : Taxa were categorized into groups by hearing categorized into groups by hearing

functionfunction

Composite data (see: Richardson Composite data (see: Richardson et alet al., 1995; Kastelein ., 1995; Kastelein et alet al., 2002) ., 2002)

Human Hearing: Weighting Human Hearing: Weighting FunctionsFunctions

10 100 1000 10000

Frequency (Hz)

0

20

40

60

80

100

120

140

Le

ve

l (dB

re 2

0 u

Pa

)

Human(M AF)

C-w eighting(inverted)

A-weighting(inverted)

Nominal Range of Human Hearing20 Hz – 20 kHz

(source: Harris 1998) (source: Harris 1998)

• In humans, an idealized version of the 40-phon equal loudness function (A-weighting) and 100-phon equal loudness function (C-weighting) are used to filter sound when calculating estimates of exposure.

Leatherwood, J.D., B.M. Sullivan, K.P. Shepherd, D.A. McCurdy, and S.A. Brown. 2002. Summary of recent NASA

studies of human response to sonic boom. Journal of the Acoustical Society of America 111(1, pt. 2): 566–598.

Frequency weighting improves Frequency weighting improves correlation between noise exposure correlation between noise exposure

and human responseand human response

Log

measu

re o

f an

noya

nce

Example of sound exposure Example of sound exposure relative to human hearing and relative to human hearing and

frequency weightingfrequency weighting

10 100 1,000

Frequency (Hz)

0

20

40

60

80

100

120

140

So

un

d P

res

su

re L

ev

el (d

B)

Human (M AF)

C-w eighting(Inverted)

Spectrumof Sonic Boom

(arb. dB)

A-weighting (inverted)

• A- and C-weighting admit different portions of the sonic boom spectrum (in arb. dB).• These weighting functions admit more low frequency noise than the human auditory threshold function.

Example of noise exposure* Example of noise exposure* relative to marine mammal relative to marine mammal

hearinghearing

Pinniped threshold data from: Kastak, D. and R.J. Schusterman. 1998. Low-frequency amphibious hearing in pinnipeds: methods, measurements, noise and ecology. Journal of the

Acoustical Society of America 103(4): 2216 – 2228.

Frequency (Hz)

dB (re 20uP

a)

1 10 100 10000

20

40

60

80

100

120

140

California Sea Lion

Frequency (Hz)

dB (re 20uP

a)

1 10 100 10000

20

40

60

80

100

120

140

Harbor Seal

Frequency (Hz)

dB (re 20uP

a)

1 10 100 10000

20

40

60

80

100

120

140

Northern Elephant Seal

*Sonic boom spectrum (arb. dB)

Human Frequency Weighting Human Frequency Weighting NetworksNetworks

101

102

103

104

-60

-50

-40

-30

-20

-10

0

A and C weighting

frequency (Hz)

wei

ghtin

g (d

B)

C-Weighting

A-weighting

2)9.737()5.107)(12200)(6.20(

12200log20)(

5.0225.0222222

42

10

ffff

ffA

06.0)12200)(6.20(

12200log20)(

2222

22

10

ff

ffC

H. Singleton, “Frequency Weighting Equations,” H. Singleton, “Frequency Weighting Equations,” http://www.cross-spectrum.com/audio/weighting.html, (2004)., (2004).

Weighting Functions for Weighting Functions for Animals Animals

• Weightings should improve exposure estimates • i.e., reduce the variability of correlations between dose and response

• Ad hoc weightings have been used historically• Human A- and C-weightings (whether or not they match the animals’ hearing range)

• Species-typical auditory threshold functions ( “O-weighting” for owls [Delaney et al. 1999], “R-weighting” for laboratory rats [NIH]).

• “Flat” weighting

o Rectangular weighting constrained by the upper and lower boundaries of the measurement system.

• Rectangular weighting constrained by the upper and low boundaries of the animal’s hearing range.

• The 1/3-octave band with the greatest energy

Threshold WeightingThreshold Weighting

The absolute auditory threshold The absolute auditory threshold function (audiogram) has been function (audiogram) has been suggested as a surrogate weighting suggested as a surrogate weighting function for marine species exposed to function for marine species exposed to underwater sound (Malme 1990; underwater sound (Malme 1990; Heathershaw et al. 2001; Nedwell and Heathershaw et al. 2001; Nedwell and Edwards, 2002; Nedwell et al, 2005) as Edwards, 2002; Nedwell et al, 2005) as well as terrestrial animals (Delaney et well as terrestrial animals (Delaney et al. 1999; Bjork et al. 2000) al. 1999; Bjork et al. 2000)

The utility of this approach has not been The utility of this approach has not been tested empirically. tested empirically.

Weighting Functions for Weighting Functions for Marine Mammals Marine Mammals

• S3 WG90 is developing recommendations for marine mammal weighting functions, but adequate science is needed to produce standardized, taxon-specific weightings

• In the interim, a simple, conservative weighting scheme was developed for marine mammals

M-WeightingM-Weighting

))((log20)(

2222

22

10highlow

high

ffff

fffM

Species GroupSpecies Group fflowlow ffhighhigh

Low-frequency cetaceans

7 Hz7 Hz 22 kHz22 kHz

Mid-frequency Mid-frequency cetaceans cetaceans

150 Hz150 Hz 160 kHz160 kHz

High-frequency High-frequency cetaceans cetaceans

200 Hz200 Hz 180 kHz180 kHz

Pinnipeds in Pinnipeds in water water

75 Hz75 Hz 75 kHz75 kHz

Pinnipeds in airPinnipeds in air 75 Hz75 Hz 30 kHz30 kHz

The frequency cutoffs can be obtained from anatomical studies. The numbers here are

conservative estimate of the upper and lower boundaries for the most sensitive members of each group.

Functional Hearing Group

EstimatedAuditory

Bandwidth

Genera Represented(# species/sub-spec.)

Frequency Weighting Network

Low-frequency cetaceans

7 Hzto

22 kHz

Balaena, Caperea, Eschrichtius, Megaptera, Balaenoptera

(13 species/sub-spec.)

Mlf (lf: low-frequency

cetacean)

Mid-frequency cetaceans

150 Hzto

160 kHz

Steno, Sousa, Sotalia, Tursiops, Stenella, Delphinus, Lagenodelphis,

Lagenorhynchus, Lissodelphis, Grampus, Peponocephala, Feresa, Pseudorca, Orcinus, Globicephala,

Orcacella, Physeter, Kogia, Delphinapterus, Monodon, Ziphius,

Berardius, Tasmacetus, Hyperoodon, Mesoplodon

(56 species/sub-spec.)

Mmf (mf: mid-frequency

cetaceans)

High-frequency cetaceans

200 Hzto

180 kHz

Phocoena, Neophocaena, Phocoenoides, Platanista, Inia,

Lipotes, Pontoporia, Cephalorhynchus

(18 species/sub-spec.)

Mhf (hf: high-frequency

cetaceans)

Pinnipedsin water

75 Hzto

75 kHz

Arctocephalus, Callorhinus, Zalophus, Eumetopias, Neophoca, Phocarctos, Otaria, Erignathus,

Phoca, Pusa, Halichoerus, Histriophoca, Pagophilus,

Cystophora, Monachus, Mirounga, Leptonychotes, Ommatophoca,

Lobodon, Hydrurga, and Odobenus(41 species/sub-spec.)

Mpw (pw: pinnipeds in

water)

Pinnipeds in air

75 Hzto

30 kHz

Same genera as pinnipeds in water(41 species/sub-spec.)

Mpa (pa: pinnipeds in

air)

These groups are relatively heterogeneous – it was the breakdown that is supported with available data.

““M-weighting” for cetacean M-weighting” for cetacean hearinghearing

10 100 1,000 10,000 100,000

Frequency (Hz)

-20

-15

-10

-5

0

5

Re

lativ

e L

ev

el (d

B)

HumanC-w eighting

M ysticete

M id-FrequencyO dontocete

H i-FrequencyO dontocete

Low-frequency cetaceans - flow: 7 Hz, fhigh: 22 kHz

Mid-frequency cetaceans - flow: 150 Hz, fhigh: 160 kHz

High-frequency cetaceans - flow: 200 Hz, fhigh: 180 kHz

The resulting family of weighting functions should yield metrics that are most relevant for high-amplitude noise exposures (where loudness functions are expected to flatten) and are likely conservative.  

““M-weighting” for pinniped M-weighting” for pinniped hearinghearing

10 100 1,000 10,000 100,000

Frequency (Hz)

-20

-15

-10

-5

0

5

Re

lativ

e L

ev

el (d

B)

PinnipedIn-Air

P innipedUnderw ater

Human C-w eighting

Note that we are not taking into account the differences in best sensitivity among species.

ConclusionsConclusions The Noise Exposure Criteria Group has developed The Noise Exposure Criteria Group has developed

weighting procedures for exposure metrics that will weighting procedures for exposure metrics that will be used as criteria forbe used as criteria for injury injury behavioral disruptionbehavioral disruption

Noise exposure metrics for humans have proven to Noise exposure metrics for humans have proven to be more effective when they account for be more effective when they account for psychophysical properties of the auditory system, psychophysical properties of the auditory system, particularly loudness perception. particularly loudness perception.

The Group has proposed to weight noise data by The Group has proposed to weight noise data by functions that admit sound throughout the frequency functions that admit sound throughout the frequency range of hearing in five marine mammal groupings. range of hearing in five marine mammal groupings.

This procedure is considered conservativeThis procedure is considered conservative The “precautionary principle” is always used in developing The “precautionary principle” is always used in developing

criteria for species at risk. criteria for species at risk. Empirical data are essential to finding better estimators of Empirical data are essential to finding better estimators of

exposure including refining the cutoff frequencies for the exposure including refining the cutoff frequencies for the weightingsweightings. .

ReferencesReferences Bjork, E., T. Nevalainen, M. Hakumaki, and H.-M. Voipio. (Bjork, E., T. Nevalainen, M. Hakumaki, and H.-M. Voipio. (20002000). R-weighting provides ). R-weighting provides

better estimation for rat hearing sensitivity. Lab. Anim. better estimation for rat hearing sensitivity. Lab. Anim. 3434,136–144. ,136–144. C. M. Harris, C. M. Harris, Handbook of Acoustical Measurements and Noise ControlHandbook of Acoustical Measurements and Noise Control, 3, 3rdrd ed., Acoustical ed., Acoustical

Society of America, 1999.Society of America, 1999. R. A. Kastelein, P. Bunskoek, M. Hagedoorn, W. W. L. Au, and D. de Haan, “Audiogram of R. A. Kastelein, P. Bunskoek, M. Hagedoorn, W. W. L. Au, and D. de Haan, “Audiogram of

a harbor porpoise (a harbor porpoise (Phocoena phocoenaPhocoena phocoena) measured with narrow-band frequency-modulated ) measured with narrow-band frequency-modulated signals,” signals,” J. Acoust. Soc. AmJ. Acoust. Soc. Am., 112(1), 334-344, 2002.., 112(1), 334-344, 2002.

D. Kastak and R.J. Schusterman, Low-frequency amphibious hearing in pinnipeds: methods, measurements, noise and ecology, J. Acoust. Soc. Am., 103(4), 2216 – 2228, 1998.

Heathershaw, A.D., P.D. Ward and A.M. David. 2001. The environmental impact of underwater sound. p. 1-12 In: 2nd Symp. on underwater bio-sonar and bioacoustic systems, Loughborough Univ., July 2001. Proc. Inst. Acoustics 23(4). Inst. of Acoustics, St Albans, Herts, U.K. 202 p.

J. D. Leatherwood, B.M. Sullivan, K.P. Shepherd, D.A. McCurdy, and S.A. Brown, “Summary of recent NASA studies of human response to sonic boom,” J. Acoust. Soc. AmJ. Acoust. Soc. Am., ., 111(1, pt. 2), 566–598, 2002.

J. Nedwell, B. Edwards, 'Measurements of underwater noise in the Arun River during J. Nedwell, B. Edwards, 'Measurements of underwater noise in the Arun River during piling at County Wharf, Littlehampton', Subacoustech Report Reference: 513R0108, piling at County Wharf, Littlehampton', Subacoustech Report Reference: 513R0108, http://www.subacoustech.com/downloads/513R0108.pdfhttp://www.subacoustech.com/downloads/513R0108.pdf, August 2002., August 2002.

J. Nedwell, J. Lovell, A. Turnpenny, “Experimental validation of a species-specific J. Nedwell, J. Lovell, A. Turnpenny, “Experimental validation of a species-specific behavioral impact metric for underwater noise,” J. Acoust. Soc. Am., 118(3), 2005.behavioral impact metric for underwater noise,” J. Acoust. Soc. Am., 118(3), 2005.

W. J. Richardson, Jr., C. R. Greene, C. I. Malme, D. H. Thomson, W. J. Richardson, Jr., C. R. Greene, C. I. Malme, D. H. Thomson, Marine Mammals and Marine Mammals and NoiseNoise, Academic Press, 1995., Academic Press, 1995.

H. Singleton, “Frequency Weighting Equations,” H. Singleton, “Frequency Weighting Equations,” http://www.cross-spectrum.com/audio/weighting.htmlhttp://www.cross-spectrum.com/audio/weighting.html, (2004)., (2004).

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