As legend has it, the Brown Note is an infrasonic frequency believed to resonate through human body parts and cause a loss of bowel control. Some protesters are convinced that Denver police will amplify such low frequencies to subdue them in August.

"They'll bring out all the technologies they can get their hands on," says activist Ben Yager. "I wouldn't put anything past police in terms of crowd control."

Sounds paranoid?

Maybe. But Mayor John Hickenlooper's administration is only fueling conspiracy theories by refusing to disclose what equipment it's buying with $18 million in federal money. Even after being sued last week, the city insists on keeping its list a secret.

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Beware of the Brown Note.

That's the word among some political activists as the Democratic National Convention nears.

"Commenting on specific security preparations is not helpful to ensuring their effectiveness," says city spokeswoman Sue Cobb.

In May, council members gave their nod to major expenditures such as a new SWAT vehicle, communications equipment and an amplification system. Rather than any serious discussion about why such big-ticket items may be needed, the council's safety committee instead chose to crack jokes.

"I'm not quite sure I know what a SWAT vehicle is all about," said Councilwoman Jeanne Faatz.

"Can we use it for insects?" quipped Councilman Doug Linkhart to much guffawing.

The city flat-out refuses to say how it plans to use the $385,000 amplification system that council members approved with little public discussion. That's why activists like Yager are buzzing about the Brown Note, real or imagined, and sonic weapons that cities such as New York have mounted on SWAT trucks to control protesters.

The source of much chatter is Glenn Spagnuolo, co- founder of the Re-create 68 activist alliance and who claims to have inside information about the Police Department's cache of so-called less-lethal weapons - a term as absurd as "low-fat Oreo."

As Spagnuolo tells it, the list includes new Taser guns that stun people for 20 seconds (as if the 5 seconds in the good old days wasn't long enough).

Activists also prognosticate that Denver will dispatch the mother of all less-lethal weapons - a microwave ray gun said to cause a burning sensation in the skin. The Pentagon hasn't used the system in Iraq, lest it be accused of torture. Lefty activists speculate that Raytheon is seeking to test a limited-range civilian version for domestic crowd control in Denver this summer.

"That, we think, is not a conspiracy theory," says Re-create 68 co-founder Mark Cohen, 62, who cut his teeth in activism when the highest technology that protesters feared was wooden billy clubs.

In a letter to the city Tuesday, Hickenlooper touted the convention as a "tremendous marketing opportunity" for Denver. Being the skilled marketer that he is, you would think the mayor would be the first to put an end to wild speculation about his police and their new bowel-moving sci-fi toys.

Unless, of course, it's true.

In which case I would remind the mayor that we aren't hosting a war but a convention - and a purportedly democratic one in a time of turmoil and widespread distrust of government and its all-too- heavy hand and secretive ways.

Susan Greene writes Sundays, Tuesdays and Thursdays. Reach her at 303-954-1989 or greene@denverpost.com.