... it is interesting to see what how their motor compares to the silent-wave machine.
Unfortunately, it doesn't compare well, at least from the 17-50/2.8 I bought and then returned. To be fair, I returned it more because it appeared to have an optical problem (sample-related). But the lens's focusing disappointed me.
I had actually ordered the older screw-drive one as I had read it actually focuses faster on many bodies than the ones with the "built-in motor" (BIM) as Tamron labels on the box. But B&H ran out of them and substituted at no additional cost the BIM one.
Compared to my AF-S lenses, the Tamron was definitely noisier but quieter than most of my screw-drive lenses. The AF-S lenses focus with a soft whisper. The Tamron did an electronic "eh" or a whir, sometimes followed by a strange fine-tuning "eh-eh-eh." Probably no louder than my screw drive lenses and quieter than some of them.
My AF-S lenses focused faster, though the Tamron wasn't horribly slow to focus either. The major exception was when te Tamron wanted to do the "eh-eh-eh" as it struggled to lock down a precise focus -- that was significantly slower and worse than some of my screw drive lenses.
The real issue is that the Tamron's BIM is a conventional micro-motor, not a ring-type, ultrasonic motor as in most AF-S lenses. Does Tamron even have a lens with an ultrasonic motor yet?
Canon owners have noted for years that their Tamrons with the micro-motors generally don't focus as quickly and are usually louder than their true USM lenses.