This sentence is supposed to be ambiguous. However I cannot see the ambiguity.

"We heard Mr. Vaughn’s voice on the loudspeaker"

My interpretation is:

We: SUBJECT

Mr. Vaughn's voice: DO

On the loudspreaker: ADV.ADJUNT


Solution 1:

It's not ambiguous. I suppose you could go way out in left field and claim that you heard the voice while you were sitting on the loudspeaker, but that would be a stretch beyond ridiculous.