He only gets quiet when he eats.
* Is this acceptable?
He only becomes quiet when he eats.
He is quiet only when he eats.
How about :
He only becomes silent when he eats.
He is silent only when he eats.
"silent" is okay.
A good part of the reason I didn't like your original sentence very much is that it could be interpreted as 'He only gets to enjoy (peace and) quiet when he eats.' That is why I prefer 'becomes' or 'is'. With the latter two verbs, there is no chance of misinterpretation.
First, as mentioned, it is better to remove however small a chance of ambiguity. So the simplest way to accomplish that is to substitute 'becomes" for "gets".
Then, I think "is" is best because of its simplicity and appropriateness. But that is not to say that "becomes" is wrong.
When we want someone to be quiet, we say 'be quiet', not 'get quiet' or 'become quiet'.
Finally, the best place for "only" is before "when he eats".
Last edited by 2006; 13-Nov-2007 at 00:33.