I see a lot of photographers wearing or carrying hard hats to the red shirt protests. But the essential gear is a set of earplugs.

Today the reds threw out a solid wall of noise as they rolled down Silom Road, home to the Patpong night market, on trucks and motorbikes. Whistles, horns, foot-shaped plastic clappers, megaphones, car radios, loudspeakers stuck at voice-of-god volume . . . I screwed two pieces of foam into my ears and marveled at the cacophony.

The reds seemed welcome on Silom, which surprised me. Many of the people lining the street clapped or waved flags. “People think this is a yellow area,” a vendor called Jui told me. “It’s not.” Maybe. Earlier, a colleague had watched riot police and soldiers arrive. Silom people applauded them too.

Parked nearby, on Rajadamri Road, was a military Humvee. Bizarrely, the driver had apparently abandoned the vehicle, leaving some red shirts to guard it. Mounted on its roof was a speaker-type device, featureless and sinister, called an LRAD Extreme.

LRAD stands for long-range acoustic device, which Softpedia describes as “a sonic blaster which concentrates a wave sound on a person at incredibly high volumes.” First used to repel pirates from a cruise liner, and later deployed by US troops in Iraq to flush insurgents from buildings, this evil little gadget can hit you with 151 dB. This, boasts its American maker, is “the equivalent of a gunshot detonating right next to your ear.” The human pain threshhold is 130 dB.

And the Thai pain threshhold? There are no reports that the military here has used the LRAD on the red shirts yet. Then again, perhaps it has been used and nobody noticed.