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Do earplugs not work for these?

As long as the frequency is between 1 and 10kHZ then well fitting earplugs should reduce the pressure level by 20 to 30dB. If you combine with earmuffs or noise cancelling headphones then that could approach 40dB [1]. Indeed the manufacturer of one system recommends that operators use hearing protection such as earplugs [2].

[1] http://scienceandglobalsecurity.org/archive/sgs09altmann.pdf

[2] http://www.adsx.co.za/information/faq-2/

Nope, your skull picks up the ultrasonic vibrations and delivers them to your eardrums. Kinda like bone-conduction headphones.

The article claims that the LRADs in use do not use ultrasonics. However this is a good point for other directed-sound weapons that might be in use.

I was getting this confused with a different tech then. https://www.youtube.com/watch?v=HF9G9M0cR0E&t=170

Ultrasonic? I thought the whole point of these devices is to produce ear-splitting tones that can actually be heard by humans.

From the article:

> According to a detailed teardown of the LRAD 300X posted by another audio technician, the LRADs produced by Genasys, the company that pioneered the devices, do not use an ultrasonic beam to project sound. However, Rife and Liberti say their design would still be effective against these hyper-directional blasts.

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