As usual I'm catching up on the Digest only infrequently; so here is my
late two cents on this subject, last discussed in the 110620 MMD.

What probably would be a close-to-perfect solution is this.  Why don't
collections/museums offer two different varieties of guided tours:
silent one and a free-speaking one?  Accordingly, visitors can choose
which type they would like to attend.  But, as was already pointed out,
the silent one would have to be enforced as truly silent.  This might
require retraining of museum staff.

I. Krause
Surrey, BC, Canada