The gemara (Kesubos 5) darshens the pasuk in Ki Keitzi, "V'yated t'hiye lecha al azeinecha," as a hint that one should use one's fingers to plug up one's ears (azeinecha is read as if it said oznecha) to avoid hearing lashon ha'ra. The gemara writes as well that Hashem gave us soft earlobes so we can plug up our ears. The Chofetz Chaim (Klal 6) derives a chiddush from this gemara: Just hearing lashon hara, even without giving credence to what is said, is assur. That's why the only way to avoid the issur is to stop up one's ears -- just not believing or not paying attention is not enough. The Chofest Chaim goes so far as to raise the possibility of this even being an issur d'oraysa -- pretty scary.
Both the Maharal and the Ben Yehoyada raise the question of why two blocks -- the fingers and the earlobe -- are needed. See Gilyon haSha"s of R' Yosef Engel to Shabbos 108 who points out that before netilas yadayim there is a problem of sticking fingers in the ear or other body orifices, but perhaps there is no problem of blocking the ear with the earlobe. The Ben Yehoyada writes simply that perhaps the double protection is meant to teach us the severity of the issur of listening to inappropriate words. Without going into what he says, I just want to point out that the Maharal puts his discussion of the sugya in Nesiv haTzeniyus (ch 2) of all places. Why would you put a lashon ha'ra discussion in Nesiv haTzeniyus? Why not put it in Nesiv haLashon?
Maybe I'm reading too much into it, but I think we see from the Maharal that tzeniyus means more than how you dress -- it means being a private person. Someone who is obsessed with hearing about the comings and goings and doings of others, someone who orients himself/herself by what he/she hears going on outside, lacks that inward focus that defines the trait of modesty.