Has anyone else faced this problem? My car makes this droning noise when I'm accelerating around 20mph *30-40 km/hr. It doesn't happen all the time, mostly when I'm going uphill. I manage to record the noise - see attached. My local mechanic is stumped at the problem as well. He's inspected the exhaust system and tightened up the bolts but can't seem to find the root cause of the problem. Any advice would be greatly appreciated!

 

YES! I'm experiencing what seems like the same noise from my ES300h. I've had the car a year and yesterday was the first time I'd heard it. First occurrence was was very prominent while pulling away from stop sign. Although not as loud, I can pretty much duplicate it at will now under load at about 2200 rpm. Something unique to hybrids? It's due for one service so will be calling dealership today.

EDIT: I've only experienced the noise intermittently since posting this comment. Finally got the vehicle into the dealership while able to consistently duplicate the noise. Exhaust heat shield was distorted (maybe from road debris?) and touching the exhaust pipe. Dealership repaired the heat shield and noise is gone.

 

Yeah, this is my first hybrid. Never encountered this problem before. Let me know if your dealership is able to find the cause of this noise!

 

I had a similar noise, it ended up being a combination of three heat shields. One around the main CAT (clamped the whole thing with a large stainless hose clamp, as the bolts are top-facing..this one sounded closest to your noise), the second was the heat shield bolted to the exhaust manifold and extends down the firewall tunnel. I had to weld a stud/washer in place while under the car to fix it as the original stud was rusted into a thread-less cylinder. The third was the heat shield on the car-side of the firewall tunnel above the exhaust 'down' pipe. I had to install some extra fender washers to re-clamp it.