Northwest National Marine Renewable Energy Center (NNMREC)

November 4, 2010Passive AcousticsNew Environmental TechnologiesRenewable Ocean Energy and the Marine EnvironmentBrian Polagye, Chris Bassett, and Jim ThomsonUniversity of WashingtonNorthwest National Marine Renewable Energy CenterNNMREC1Need for New Environmental TechnologiesPassive AcousticsIntroductionAmbient NoiseEnvironmental EffectsNNMRECMarine Energy DevelopmentUncertainty around the potential environmental effects of marine energy poses a barrier to developmentConsensus that well-monitored pilot projects are a first step in reducing environmental uncertainty

Courtesy of Marine Current Turbines

NNMRECPilot Monitoring: Wish ListMonitor the full range of potential stressor (e.g., noise) and receptor (e.g., marine mammal) interactionsDiscriminate changes caused by marine energy pilot projects from large natural and anthropogenic variabilityRobust, species specific identificationProvide information for decision making in real timeMonitor over a range of time scales (seconds to years) and length scales (cm to km)NNMREC4Pilot Monitoring: RealityResources are scarce and monitoring needs must be prioritized based on riskSome interactions will not be measurable at the pilot scaleConditions at marine energy sites preclude or complicate many conventional methodsIntegrating multiple, rich data streams is a major software challengeNNMRECNeed for New Environmental TechnologiesPassive AcousticsIntroductionAmbient NoiseEnvironmental EffectsNNMRECPassive AcousticsBroadband noiseExisting, ambient noiseNoise from marine energy projects Marine mammal echolocationSpecies specificPresence or absenceMature Technology, New Applications

NNMRECRecording HydrophoneDeployments for three months at a time on seabedSample ambient noise1% duty cycle20 40,000 HzLoggerhead DSG

NNMRECNeed for New Environmental TechnologiesPassive AcousticsIntroductionAmbient NoiseEnvironmental EffectsNNMRECAmbient Noise Sources

NNMRECAmbient Noise Characteristics

NNMRECAmbient Noise VariabilityWhat is the context for this variability?

NNMREC

Establishing Context: Shipping

Automatic Identification System (AIS)ffffffffffffssNNMREC

Acoustic Doppler Current Profiler (ADCP)Establishing Context: CurrentsNNMRECMeasuring Noise in Strong CurrentsWhen currents exceed 1 m/s, elevated, broadband noise masks other sourcesTwo contributors to this increasePropagating noise Pseudo-noise and self-noiseWhen currents exceed 1 m/s, most hydrokinetic turbines begin to operateBassett et al., Characteristics of underwater ambient noise at a proposed tidal energy site in Puget Sound, MTS/IEEE Oceans 2010, Seattle, WA, September 20-23.NNMRECNeed for New Environmental TechnologiesPassive AcousticsIntroductionAmbient NoiseEnvironmental EffectsNNMRECSource-specific Received Levels

NNMRECEvaluating Sound Transmission Loss

RL = 179 18.4 log10(d)Source level at 1mTransmission losscoefficientReceived levelDistance from sourceNNMRECEstimated Project NoiseTwo turbinesSource level for each turbine = 160 dB re 1 Pa at 1 mSources are incoherentSame transmission loss as noise from ferry

0.5 km1.0 kmNNMRECConclusionsPassive acoustics are a powerful tool for evaluating and monitoring acoustic effects of marine energy projectsMost effective when combined with additional tools to establish contextNNMRECThank YouMore information available at:

http://depts.washington.edu/nnmrecNNMREC21