Some good news in improving technologies!

Perhaps one of the more salient benefits of our work on ocean noise pollution is that unlike solid and chemical pollution, when the noise goes away, it is gone. This gives us reasons for optimism, particularly as we see efforts to improve technologies and practices by a broadening base of ocean stakeholders.

The first inkling that this could happen occurred a few years back when the United Nations International Maritime Organization (IMO) issued guidelines for the quieting of ocean vessels.

Just this year the “International Quiet Ocean Experiment” brought together scientists and stakeholders to craft a cooperative plan for understanding and mitigating the impacts of human generated noise in the ocean.

Bolt E Source Airgun

Bolt Airgun

And just this month three items came across the boards. An article in Sea Technology about Ultra Electronics Sonar Systems developments of a biomimetic sonar that uses biologically derived signals instead of synthetic or digital signals. The article examines the relative effectiveness of sperm whale echolocation clicks against synthetic signals, but it also suggests that animals would be less threatened by signals that are “natural sounding” and thus less likely to respond negatively.

Seismic Survey

Seismic Survey Array

In the same issue there is another article about the benefits of using continuous sonar signals as opposed to periodic blasts. Typical surveillance and navigation sonars kick out a blast or “ping” and waits for an echo to return off of a target. By using some advanced integration techniques the continuously active sonar can lock on to a target and track it using an equivalent amount of energy but spread over time – allowing for a decreased source level and potentially less impacts on marine life.

The third piece coming across my desk was in a local newsletter from Norwalk CT, where the seismic airgun manufacture Bolt Technologies is collaborating with Schlumberger on limiting the bandwidth and thus quieting down the collateral noise from seismic airguns. In an ideal setting the seismic signals would sound less like “bangs” and more like waves crashing, which again sounds more “natural” and should also decrease the impacts on marine life.

I spoke with John Andros with Bolt today, and while the actual product is not ready for prime time yet, they wanted to announce the project and the collaboration.

It is nice to know that some big stakeholders are taking this noise issue to heart. If we continue to move forward, pernicious ocean noise pollution could end up being “a thing of the past.”

Mitigating offshore wind farm noise

One of the hot topics at the recent International Quiet Ocean Experiment in Paris was the noise impacts of offshore wind farms. It seems that while the American Oilmen are furiously trying to carve up the Arctic for fossil fuel, the Europeans are rapidly developing wind power. Much of this is happening in the North Sea between the United Kingdom and the European continent.

North Sea Wind Farm

While wind power has significantly lower environmental impact than fossil fuel, it does not come without drawbacks. From a noise standpoint the concerns include the noise of installation, and the ongoing noises of operation.

The operation noises include gearbox vibration transmitted down the mast, and the thumping noise generated by the tip vortices as they pass by a boundary (like the ocean surface).

Pile Driving with bubble curtain

The installation noises in the shallow North Sea are from pile-driving the foundations to mount the mast. Percussive noise from pile driving was found to be deadly to fish, and pernicious to marine mammals.

Mitigation for pile driving noise was first developed during the San Francisco Bay Area bridge retrofits and involves the use of “bubble curtains.” By surrounding a driving pile with a ring of air bubbles, the water and noise within the ring can be acoustically isolated from the surrounding environment.

The drawback here is that the process is energy intensive because a high volume of air needs to be continuously forced down to the depth of the seabed to be released in a continuous stream. This can get really expensive: This mandated mitigation doubled the cost of the Richmond Bridge seismic retrofit.

But researchers at the University of Texas, Austin have developed an improvement on the bubble curtain – by encapsulating the bubbles in a latex envelope, a curtain can be installed while pile driving, and then relocated when needed elsewhere.

This promising technology could decrease the expense as well as the noise of developing wind farms in the North Sea – or even off the coast of America!

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