Bells, bolts and bars are apparently unheard of.

There was a loud crack that echoed all around the concourse, apparently unheard by the milling Muggles.

And another notable fact of Christian experience underlies the parable; namely that the Church's cry for protection from the adversary is often apparently unheard.

Dietary precautions were apparently unheard of except in the case of certain chronic ailments, and then they were accepted as one of life's worst evils.