The Technion in Israel developed this "black hole," creating a well into which air flows faster than the speed of sound. That means that any sounds trying to pass through this moving air just can't keep up with the flow of the air into the "hole." Any sound wave in this air is like someone trying to run up the down escalator. But in this case, the down escalator is four times faster than the person can run.

This is achieved by two clouds of atoms (called a Bose-Einstein condensate) cooled to almost absolute zero, with a pool of very low density between them. Atoms can flow very rapidly, pretty much unhindered, into this area of low density at speeds over four times the speed of sound.

The result is a well into which all sound falls and cannot escape. Any sound that passes close enough to the "black hole" essentially ceases to be.

This sonic black hole offers scientists a method for testing their theories about black holes in general. But imagine putting one of these in your car instead of a muffler, or in a rocket. A battalion of armed soldiers equipped with a few devices like this could march anywhere silently. These sonic devices wouldn't just dampen the sound; they would virtually obliterate it. It raises the old question: if a tree falls on the Bose-Einstein condensate sonic black hole, does it make a sound?

Sonic Black Hole Traps Sound Waves via [Discovery News]
A sonic black hole in a density-inverted Bose-Einstein condensate via [arXiv]

The Phoenix team announced Monday that they’ve been given the go-ahead to turn on the Phoenix Lander’s microphone in the next week or two. Although the researchers are excited at the prospect of hearing Martian sounds for the first time, their current expectations aren't particularly high:

Phoenix scientists aren't sure just what, or how much, they'll hear. For one thing, Phoenix's mike is "not a professional microphone," [Phoenix principal investigator Peter] Smith said (he likened it to the microphones used on a standard cell phone).

For another, sound waves don't travel as far on Mars as they do on Earth because Mars' atmosphere is thinner. It would be similar to listening to sound at an altitude of about 100,000 feet (30,500 meters) above Earth's surface, Smith said.

If the team can hear Phoenix's operations, they'll then turn the microphone on while Phoenix is quiet and just see what they can hear. What that might be, Smith isn't certain.

The microphone is being activated as part of the Mars Descent Imager system, which will give NASA a closer look at the Phoenix’s discoveries even if it turns out there’s nothing to hear.

Image courtesy of NASA.

Listening In: Lander to Record Mars Sounds [Space.com]

• The first appearance of the scream was in 1951's Distant Drums, and was used when a man was eaten by an alligator.
• The sound is named the "Wilhelm Scream" after Pvt. Wilhelm gets shot in the leg by an arrow in the 1953 film The Charge at Feather River, and screams as he falls over.
• The sound was used in eight more films in the 1950s, including 1954's Them!, about giant, nuclear-mutated ants.
• The sound persisted into the 1960s, appearing in eight more movies, including the campy Hercules Against The Moon Men, where Hercules battles monsters from the moon.
• While Wilhelm started to flag in the 1970s, Star Wars sound designer Ben Burtt found a reel labeled "Man Being Eaten By Alligator" in the Warner archives and used the sound when Luke shoots a Stormtrooper who falls down a shaft in the Death Star.
• Burtt later tracked the sound back to its original use in Distant Drums, although he was the first to call it the "Wilhelm Scream."
• The sound has since been featured in every Star Wars and Indiana Jones movie. In fact, it was even used in The Star Wars Holiday Special.
• It's a mystery as to who the actor was that recorded the original scream, but the most likely suspect is character actor and singer Sheb Wooley, whose name appeared on a memo as a sound extra for Distant Drums. He's best known for his hit song "The Flying Purple People Eater".
• The sound has been used in over 75 movies (most recently in Cloverfield), dozens of television shows (like Doctor Who), and even numerous video games... including many of the Star Wars titles.

The problem with the Thunderscreech was that the supersonic propeller blades would cause rapid-fire shockwaves, even when the plane was sitting on the ground. Test pilots refused to take it up, and officials would order it to be towed far from the test center before firing up the engines, and only one of the two prototypes ever flew, logging only 10 hours. Why? Because those shockwaves would case nausea, spasms, seizures, and loosening of the bowels. What a ride. You can hear the otherworldy banshee wail of one here.

So the word spread that the soundwaves generated by the engines were causing the pooping, and like a game of telephone, soon folks began believing there was a secret low frequency that could unlock the human sphincter. NASA performed tests of low frequencies because they were worried their astronauts might start crapping out upon launch. They mounted cockpit seats on vibration tables that were blasted with 160 decibels in the range of 0.5 hertz to 40 hertz, but no one sounded off into the brown. Even more recently companies have built extremely massive subwoofers that have failed to make anyone prairie dog it, despite the massive amounts of low frequencies being pumped out.

Although this hasn't stopped it from seeping into poopular culture, probably most famously in Transmetropolitan, where Spider Jerusalem carries a Bowel Disruptor that operates on the brown note principle. It even has settings from "diarrhea" to "prolapse." Ouch. Although it was probably ripped off from Steve Meretzky's (of Infocom fame)The Superhero League of Hoboken computer game from 1994, Spider put it to a lot better use. In fact, Ben Folds used the brown note with Improv Everywhere in a 1996 concert hoax involving diapers and chocolate syrup. Now that's entertainment. Mythbusters even tackled the legend on an episode, and they recorded no poop at all.

So, until science comes up with a new method for causing uncontrollable evacuation, bowel disruptors will sadly remain science fiction and not fact. Which is a real pity, because we sure could have used one during the upcoming presidential elections. We'll have to just stick to vomit guns.