Why is my dryer louder than it used to be?
A sudden change in dryer noise is most often one of three things: drum rollers wearing down (a rhythmic thumping), a failing blower wheel (a high-pitched whine), or debris stuck in the lint-screen housing (scraping or rattling). None of these are vent-related, but all of them are worth investigating before they escalate.
Rhythmic thumping or banging (gets worse over weeks): drum rollers or idler pulley. Drum rollers are rubber wheels that support the drum; they wear down over 8–12 years and become flat-spotted. Replacement is straightforward but requires opening the dryer cabinet — usually a service call.
High-pitched whine or squeal (constant while running): blower wheel or motor bearings. The blower is the fan that pushes air through the vent. If it's loose, cracked, or lint-packed, it howls. This one we sometimes catch during a vent cleaning — if the blower housing is full of lint, we can usually clean it in the same visit.
Scraping or rattling: something in the lint-screen housing. Socks, coins, underwire from bras. Pull the lint screen and look with a flashlight; if you see something, stop the dryer and book service — don't run it with foreign objects in the blower path.
None of these are directly vent-related. But the underlying cause of accelerated dryer wear is often a restricted vent making the motor work harder — so if you haven't had a vent cleaning recently, that's still the first step.
Manufacturer resources
Official support pages for brands commonly referenced in this answer.