Page 37: of Maritime Reporter Magazine (August 2023)

EMISSIONS REDUCTION, MEASUREMENT "The unnecessary complicatedness of the

EEXI calculations speaks to maybe there's a simpler way ... and if what you're after is broad compliance, you want to make things as easy as possible."

Don MacPherson

Technical Director, HydroComp

The reverse is true for underwater radiated noise, where you have remote test facilities, which are expensive and are not common. Each facility is unique, so how do you calibrate everything to have a fair playing ? eld. There's a whole host of reasons why this has greater uncertainty in the test. Be- cause you have computations for correcting reception, which is what you actually record with the transducers back to a common source level. So what you're looking for are sound pressure levels at the source. Because that's the only common place that you can establish a benchmark that you can then establish a compliance regulation against.

My thinking is that a rules-based approach – similar to how classi? cation societies use rules for a propeller blade strength, or structural properties of a ship, or even damage stability calculations; we don't test a ship to damage in order to deter- mine whether it's going to be safe or not. We use a rules- or a calculations-based approach, and I would propose for under- water radiated noise that is going to be the way to achieve the greatest compliance.

They say that 80% of the cost of a ship is determined in the ? rst ? ve to 10% of the work. Which makes sense because you lock in so many things about whole geometry, propulsion options, at the outset. All of the characteristics of a ship are locked in during that initial design, and if we can include un- derwater radiated noise, greenhouse gas emissions and those sorts of things early in the design process, we are going to achieve broader international compliance than we could with testing. It's going to be faster, it's going to be cheaper, and ultimately, it's going to be more fair, collectively. www.marinelink.com 37

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