Dannys lethal weapon

Danny just came to visit. He's a computer expert. He has this crap little Peugot compact car with a sound system that is worth three times what the car is.
"Come and look at this Mike." he says. He goes to the back of the car and opens the hatchback boot. There is no boot anymore it's one massive, fuck off speaker, made of inch thick MDF, with stainless steel baffles and an 18" speaker. The wires leading to the amplifier are as thick as my thumb. "Cool huh?"
"That speaker is twice the size of our stage speakers."
"Twice as loud as well. Listen to this." and he grabs his remote and points it at the front of the car. I almost leap three foot into the air as the sound hits me, drum and bass.
"Fuck that's loud."
"Nah that's only low volume. that's driving about volume."
"What you drive about listening to music that loud? How's your hearing?"
"OK."
"What the hell do you want all this for?"
"Competitions. I've won the last three I've entered. I'm going to Donnington tomorrow and I reckon I'm going to win."
"How does that work? What sort of music do you play?"
"Oh you don't play music in the competition. It's a special noise. An oscillation frequency. It's on for two seconds. Wanna hear it?"
So I'm standing at the open door of his car while he sits in and fiddles with the stereo controls finding the special track, I'm not even in the car, when he switches it on. no warning.
Blam!!!!! The sound nearly knocks me off my feet, it goes straight through me, suddenly I feel sick and dizzy, every part of my body shakes with the resonance of the noise, it lasts two seconds but feels like more.
"Wanna hear at full volume now?" I am too stunned to reply as he slips out from the seat and hits the button again. BLAM!!!!!! Fuck! That's not a car stereo it's a fucking weapon. I'm near helpless as the sound rips through me again. "Cool huh?" Danny says. I am speachless. My whole body has turned to jelly, I feel unsteady on my feet. "That's about 146 decibels." he went on.
Apparently he's in one of the lower competition groups. In the higher groups they have multiple speakers and get up to 160 decibels. But in his group it has to be a standard un modified car and the speakers must be below the level of the windows.
He's gone now and I'm still shaking. It would be a great tool for crowd control stopping riots. Blast them with sound and reduce them to a quivering wreck. I'm sure it would work.

Whisper on dudes. Pardon? What did you say? Sorry I can't hear you. Somethings happened to my hearing.