[El Gato]

A good set of earplugs that cost 25 cents will make it completely ineffective.

Well, probably not. For one thing earplugs only give you 10-15 dB of suppression, so that 150 dB "warning" mode is reduced to 135 to 140 dB. For another sound levels like 150 dB are felt as much as heard, depending on the frequency. Scramble your insides they might.

Still I'd prefer a nice 20 mm Gatling, or for a ship as big as a those cruise ships, maybe a 30 mm similar to the GAU-8 carried by the A-10. Private yachts and the like should carry a pair of Ma Dueces, if not maybe more. Clearly though, even the 20 mm, even in a single barrel automatic would be plenty for boats such as the one shown, and some quite a bit larger as well.

[DB]

Well actually not.

Those are the mean attenuations and the standard deviation is around 4 dB. If used improperly then all bets are off.

In addition, I use these earplugs every night. I have a sound level meter. I have experience in sound reenforcement so I have some understanding of sound pressure levels and what they are like along with relative levels.

And, 150 dB is at the source. From a ship deck the distance would be likely at least 50 feet attenuating the sound substantially. The article already says that it sounds similar to a smoke detector so the frequencies involved are not low. So no "scrambling of your insides" is likely. Only slight surface heating perhaps.

I've been in enclosed areas with average sound pressures exceeding 125 dB - with ear protection. Very loud... You can feel every hair on your body... If feels like they are all being touched/brushed at the same time... I blurs your vision... It's pretty amazing ;-)

[DB]

I should add the audio frequencies used have to be somewhat high in order to direct it selectively to a target.

[DB]

As far as actual weapons go, I agree. Use real guns.

[Enchante]

"maybe a 30 mm similar to the GAU-8 carried by the A-10"

YEAH, that'll leave a mark! Might be a bit of overkill, though, since they'd never find the shreds of terrorist tissue.....