Yes, a multi-tap transformer connected at a higher voltage will make the chime louder.
Hows that? Does it hit the bell any harder? I didn't notice the last time I did that, (by accident) but it didn't last very long. (I 24'ed a 16...)
Anyway I recently had an older lady customer complain about her chime over the phone to me - that "it doesn't work" so I showed up, and without thinking - I rang it, and I could hear it out front. There I was standing with a possible replacement in hand.... (Nutone Ding Dong) NOBODY ANSWERED - rang again... Remembering my earlier phone conversations when she told me the doorbell didnt work , she told me to call... Wanting the service call closed, I called, and I could hear her old Ma'Bell phone out front. (The type with a BELL inside...)
The lady comes out, and we talked about her chime, and I said it worked... She didn't hear it... Walked inside and she had the exact same one that I had in my hand. I told her that the one I had wasn't goning to be any louder than the one she already had, then we started talking about why she can hear the phone... I had an idea, and we went for it... I hollowed out the old chime and put a 4" bell in it. When I was done it sounded like the end of lunch in elementary school, and she said it was just loud enough....