*sigh* She doesn't neccasarily have to scream for her echo location to work. it could be something as subtle as a snap of her fingers, or even surrounding sounds from other things, as long as it produces sound within the hearing range of humans. like a car going by, or talking. Plus I think you over estimate the human's sense of sight. sight wouldn't work if you couldn't hear or feel. the only reason we think it is so important is because we have been conditioned to use it so much.
FAIR : The City