what does the fourth amendment do?
Katz v. U.S., 389 U.S. 347, 51 ('67) (finding a lesser expectation of privacy in personal effects that 'a person knowingly exposes to the public, even in his own home or office'). The Fourth Amendment provides no protection for what 'a person knowingly exposes to the public'. Like a man's facial characteristics, or handwriting, his voice is repeatedly produced for others to hear.