Odd sound

What is your question?

Loud motor running on starting, sounds like if you held the windshield wiper spray button on. Mechanic says it's a catalytic converter heater fan but I can't find any info on THAT and it runs in the summer. What could it be?

What makes this problem better or worse?

on start up. Always.

How long has your 2006 Toyota Tundra had this problem?

Maybe the last 1000 miles