“It is a basic principle of due process (Amendment V) that an enactment is void for vagueness if its prohibitions are not clearly defined. Vague laws offend several important values. First, because we assume that man is free to steer between lawful and unlawful conduct, we insist that laws give the person of ordinary intelligence a reasonable opportunity to know what is prohibited, so that he may act accordingly. Vague laws may trap the innocent by not providing "fair warning". Second, if arbitrary and discriminatory enforcement is to be prevented, laws must provide explicit standards for those who apply them. A vague law impermissibly delegates basic policy matters to policemen, judges, and juries for resolution on an ad hoc and subjective basis, with the attendant dangers of "arbitrary and discriminatory application". Third, but related, where a vague statute abuts upon sensitive areas of basic First Amendment freedoms, it operates to inhibit the exercise of those freedoms. (the chilling effect). In one case, the court declared that numerical sound levels were constitutional as well as the term "plainly audible" provided it was associated with a reasonable distance. Two requirements for a noise ordinance provision is that: