Proposed Abstract Title

Measuring noise in biologically meaningful ways

Presenter/Author Information

Jason Wood, SMRU ConsultingFollow

Type of Presentation

Oral

Session Title

From plankton to whales: underwater noise and its impacts on marine life

Location

2016SSEC

Description

At its simplest, a hydrophone records sound by measuring small changes in ambient pressure over time. The simplicity ends there. The metrics used to assess noise effects can be bewildering and occur at different temporal resolutions, frequency ranges and weighting. In order to estimate the impacts of noise on marine life it is important that the sound metrics used are biologically meaningful. This talk will explore three themes in noise metrics; 1) what metrics are currently used, 2) how metrics are informed by biology, and 3) the tradeoffs we face between simplifying and complicating noise metrics.

Common noise metrics (sound pressure level, sound exposure level, frequency weighting, etc.) will be introduced and the implications of their use will be discussed. Noise can cause permanent and temporary hearing damage, as well as mask communication calls and echolocation clicks. These occur by different mechanisms which have been informed by captive studies under simplified scenarios. Our choice of noise metrics has been based on the results of these few studies. This talk will present evidence from wild studies which contradicts captive studies and has repercussions to how we assess noise effects. In spite of the uncertainty in which noise metrics we use, we need to move forward with noise measurements in this uncertain and quickly evolving field. Biological results will push us towards more specific (and therefore more complicated noise metrics), but we need to balance that with the need to have more standardized (and hopefully simple) noise metrics to monitor soundscapes in the long term. This argues for a current approach of standardized and simplified noise metrics, but also suggests some raw data from long term studies should also be retained so that, as noise metrics are updated, these data can be re-analyzed.

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Measuring noise in biologically meaningful ways

2016SSEC

At its simplest, a hydrophone records sound by measuring small changes in ambient pressure over time. The simplicity ends there. The metrics used to assess noise effects can be bewildering and occur at different temporal resolutions, frequency ranges and weighting. In order to estimate the impacts of noise on marine life it is important that the sound metrics used are biologically meaningful. This talk will explore three themes in noise metrics; 1) what metrics are currently used, 2) how metrics are informed by biology, and 3) the tradeoffs we face between simplifying and complicating noise metrics.

Common noise metrics (sound pressure level, sound exposure level, frequency weighting, etc.) will be introduced and the implications of their use will be discussed. Noise can cause permanent and temporary hearing damage, as well as mask communication calls and echolocation clicks. These occur by different mechanisms which have been informed by captive studies under simplified scenarios. Our choice of noise metrics has been based on the results of these few studies. This talk will present evidence from wild studies which contradicts captive studies and has repercussions to how we assess noise effects. In spite of the uncertainty in which noise metrics we use, we need to move forward with noise measurements in this uncertain and quickly evolving field. Biological results will push us towards more specific (and therefore more complicated noise metrics), but we need to balance that with the need to have more standardized (and hopefully simple) noise metrics to monitor soundscapes in the long term. This argues for a current approach of standardized and simplified noise metrics, but also suggests some raw data from long term studies should also be retained so that, as noise metrics are updated, these data can be re-analyzed.