Environmental and ship noise

measurements and modelling

David Barclay,

Dalhousie University

August 30th, 2018

Wenz curves - data derived modelSources of ambient noise

National Research Council. 2003. Ocean Noise and Marine Mammals. National Academy Press, Washington, D.C. (as adapted from Wenz, 1962) by the National Academy of Sciences

1 10 100 1000 10 000

f [Hz]

Wind

Dependent

Noise

Distant

Shipping

Noise

Precipitation Noise

Earthquakes and

explosions

Ship noise footprint modelling

Input data needed:Ship position(s)Source levelBathymetrySeabed acoustic propertiesWater column structure

Output:Noise level (x,y,z & freq)Sound exposure level

Sound Speed [m/s]

Dep

th [

m]

Range [km]2000

Favorable Arctic conditions

Bathymetry m

Noise level distributions of surface wind generated noise

NSL: mean(|p|2/A)=10-5(Pa)2, std=10-4(Pa)2

Nx2D

zr = 50 m

Noise modeling

Noise level distributions in canyonHudson Canyon Bathymetry – sources at 0.1 m

Bathymetry m

Noise level distributions of surface wind generated noise

3D

zr = 50 m

Noise modeling

NSL: mean(|p|2/A)=10-5(Pa)2, std=10-4(Pa)2

Noise level distributions in canyonHudson Canyon Bathymetry – sources at 0.1 m

Ideal ambient noise model

Captures:• Source physics, distribution statistics, surface

wind, wave, and current information.• Bathymetric effects, 3D when necessary• Accurate bottom acoustic properties• Depth and range water column variability • Non spatially uniform processes

Precipitation, ice noise, surf noise Implementation:

• Portably validatedOutput:

• Probability power spectral density• Spatial properties (directionality, coherence)

Wave generated surface noise models

Surface source strength:

WOTAN method relating wind speed to band averaged spectral level is most physics based work available.

Extend this work to shallow water and the ‘arbitrary ocean’

Directionality can be found using PE or normal modese.g. Kuperman & Ingenito, Buckingham & Deane

Vertical coherence and directionality

G12(w) =1

2F(q)e

-iwd

cCos(q )

0

p

ò Sin(q)dq

Vertical coherence Vertical noise directionality

We can very accurately model coherence (directionality) without the uncertainty of source level.

We can determine exactly the relative contributions of wind & shipping to the noise field, as a function of time & frequency.

Time series of vertical coherence

April 6 May 4Date

Imaginary vertical coherence

Real vertical coherence

Freq

ue

ncy

[H

z]Fr

equ

en

cy [

Hz]

Alvin Canyon, 2016W

ind

no

ise Time varyin

gsh

ip n

oise

Co

he

ren

ceC

oh

ere

nce

Frequency [Hz]

Wind

Wind + 10 km ship (10 modes)

Wind + 10 km shipData

0 1000 2000 3000 4000 5000

Wind and distant shipping modelling

G12wind+shipping =

G12wind + C*G12

shipping

Fit is performed by searching over C

Data–model fitting allows estimate of effective range and relative power.

Partitioning of wind and shipping noise

noise.phys.ocean.dal.ca/barrow/bsrto/

Data collected by DFO

noise.phys.ocean.dal.ca/barrow/bsrto/

Data collected by DFO

Model & measurement campaign

Data• Acoustic data: Multi-month measurements on vertical pairs of hydrophones• Meta-data: SSP, bottom loss, wave buoy, AIS, wind speed & dir., precipitation

radar, barometer, humidity, upward looking ADCP• Modeled meta-data: wind speed & dir, SSP, surface currents

Research Objectives• Collect a data set to validate a portable environmental & ship noise model • Perform sensitivity analysis of the noise model using modeled meta-data• Produce bioacoustic metric maps

Technical goals• Reproduce observations for ambient and ship noise to determine source level

model accuracy.• Determine conditions when horizontal scattering and refraction must be

considered• Apply this model in the arbitrary ocean by evaluating against data sets of

opportunity.

• Ship tracking (non-AIS tagged)

• Source level uncertainty

• Transmission loss– Model input data

– Ambient noise model

• Bioacoustics…!– Animal distributions

– Marine animal hearing sensitivity

– Behavioral & physiological response

Major challenges ahead

Starting work here…

ECHO project

Need northern community involvement.

Collective effort & hard…