[wl]

It's not so much that LRAD relies on bone conduction to inflict pain (and sensorineural hearing loss!), but that the sound levels are so high that even if you block the air conduction route with earplugs, the bone conduction route (approximately 30 dB of attenuation compared with air) still might deliver enough sound to the inner ear to cause pain and hearing loss.

This kind of thing is a problem on aircraft carriers, where people working on the flight deck are so close to loud jets that no amount of conventional hearing protection will adequately conserve hearing. Creare has been working for the last decade and a half on special helmets for the US Navy to overcome this issue, resulting in the HGU-99/P Hearing Protection Helmet.