This was the latest I had heard about the protestors:
http://bellaciao.org/en/article.php3?id_article=10046
"Bush Administration Seeks to Squelch State of the Union Protest at Capitol on January 31 January 22, 2006
World Can’t Wait Capitol Hill Office: 511 ‘C’ St. NE Washington DC 20002, Stanton Square DC PRESS CONTACT: Don Spark, 202-536-4310, donspark@worldcantwait.org
Press Conference: Monday, January 23, 9:30 a.m. National Press Club, Edward R. Murrow Room 529 14th Street, NW Washington DC
The Bush administration has expanded the special security zone around the Capitol, effectively denying a meaningful public space for a protest called by World Can’t Wait-Drive Out the Bush Regime during the State of the Union address on January 31, 2006. This action, one of many held simultaneously that night at 8pm EST in cities and towns across the country, calls for symbolically “drowning out Bush’s lies” and demands “BUSH STEP DOWN.”
At a meeting on January 10 with the National Park Service Police, Capitol Police, and National Parks Department, the World Can’t Wait was offered the area surrounding the Capitol Reflecting Pool for the January 31st gathering. This was accepted by World Can’t Wait. However, on January 19, the organization received word that this area had been reclassified as part of a “secure perimeter” for that day.
In addition, the grass areas of the National Mall have been closed for “turf renovation” up to 7th Street. Thus, the proposed demonstration area is restricted to the “gravel and concrete walkways of the national Mall between 3rd and 4th Streets.”
Travis Morales of World Can’t Wait-Drive Out the Bush Regime responded: “This so-called permit would have the effect of dispersing and disrupting this First Amendment protest by preventing a large, cohesive gathering anywhere near the Capitol. We’d have to go a mile away to 7th Street to even have a stage. We’re mobilizing people to challenge this outrageous prohibition, and we’re pursuing legal action.”
These nutjobs imagine that they have an inalienable Constitutional right to disrupt the State of the Union Address.
If they're at 3rd street, they're a quarter mile from the Capitol. Generally, a train whistle can be heard a mile away (though not loudly). However, they've also got city traffic noise, walls, glass and doors, and gallery noise to contend with.
I'd say they're not likely to be audible at the SOTU.