Silent relative adverbs as opposed to noisy ones?
Silent as opposed to non-silent.
Silent like the
that or
which which many would suppose to be tacitly present in a noun phrase with a zero relative clause like
the point I made.
If the noun phrase is changed to
the point that I made or
the point which I made, the
that or the
which is no longer silent.
Similarly, in finite relatives with relative adverbs (viz., the one in
the place where I went yesterday), we have
that- and zero-relative correlates:
the place that I went yesterday
the place I went yesterday
We also have a correlate with
which, in which correlate the relativized element is no longer a prepositional phrase but a noun phrase, and
to is needed:
the place which I went to yesterday
Or with Pied Piping:
the place to which I went yesterday
Similarly, we can have the nonfinite relatives with a tacit relative adverb (
any place to go) or a tacit relative pronoun (
any place to go to).
In the latter case, we can have Pied Piping, and, when we do, the relative pronoun, though perhaps not noisy, is no longer silent:
any place to which to go