WNYC’s new Jerome L. Greene Performance Space will make on-air hosts like Brian Lehrer and Leonard Lopate really public. The D.J.’s, guests, and studio audiences will soon be visible from the sidewalk outside the station’s Soho headquarters (now marked by an undulating news ticker and WNYC in huge, bright-red letters). The venue opens on April 28 with a ten-day festival that includes a reading by Sarah Jessica Parker, a “Soundcheck” panel featuring Lou Reed and Santigold, and a TV-versus-radio debate refereed by Ira Glass. To buy tickets or join a studio audience, go to thegreenespace.org (44 Charlton St., at Varick St.).