Loud furnace noises are more than an annoyance. They're often an early warning of a problem. Soft clicks and a gentle whoosh are normal, but banging when the furnace starts can point to delayed ignition. Screeching, grinding, or rattling can mean a worn blower motor, a failing bearing, or loose parts. Sherwood Mechanical explains what different furnace sounds usually mean, which noises call for shutting your furnace off right away, and why booking an early repair can prevent a much bigger breakdown.