Another noise question - high pitch whining/hissing from the rear (videos)

I recently noticed a high-pitched whining noise coming from the driver's rear end of my '99 tiptronic with 98k km, and I'm wondering if the experts here could guide me on next steps before I take it in. It sounds similar to the high-pitched 'brake squeak' when coming to a stop. Here's a few details: The noise is not heard when the car is idling still, whether it's in drive, park, or neutral. I can hear the whine when I rev the engine, and it starts at around 1800-2000 rpm. It's heard in all drive, park, or neutral positions with stepping on the gas. The noise occurs with the A/C on or off. I can't hear the noise from inside the cabin, only when the driver's side window is down. And if I'm next to a wall the noise bouncing back accentuates it (it's how I first noticed the noise). Doesn't seem to be coming from the passenger rear side. The car drives fine otherwise, doesn't slip out of gear, etc. 3000km ago I replaced all of the water pump, coolant expansion tank, acc belt idler pulley, tensioner pulley, and belt. Original IMS, not sure if AOS/RMS was ever replaced by previous owner. Am I correct in assuming that: It's not the wheel bearing, as the car's sitting still and not road speed dependent. It's unlikely to be transmission-related, since the noise is still heard with the car in neutral position. It may be related to one of the accessories? Many thanks in advance! https://youtube.com/shorts/nLKRsgEnnz8?si=utLpyyGKC9Gl7XkF https://youtube.com/shorts/uPTmGnyjFTg?si=ZB8I3eYTrOG2tQSh

I don't hear anything abnormal. Are you talking about the engine whine that goes up in pitch as the engine revs? That's normal on 5 chain cars (996.1), its just how the cars sound and yes it will be very noticeable in a parking garage. Search my posts for "M96 whine". If it's recently changed or become louder you should check your pulleys, water pump, and power steering fluid. My opinion is its normal.

Quotes source post: 19476409

Your post was actually one of the first to come up when I initially started googling around this The noise I'm wondering about is the faint, high pitched 'squeal' heard coming in on top of the engine whine, most prominent at the 7 sec, 10-12 sec, and 19 sec marks of the first video. Like stepping on a noisy brake. Unless that is part of the usual M96 engine whine, and expected.

May be your SAI. Start the car when cold, open your engine lid and listen to the left rear corner. That's where your SAI resides. If you hear a high pitched whine, it's your SAI. The sound will go away after your cats warm up. It's loud as he'll in the cold winter months. In warm weather you won't hear it as much because the cats warm up faster. The part is easy to replace yourself and $300-400. If you can, post as video from the engine with the lid up. The other sound which is more of a whuur vs a whine is your power steering which means your PS fluid is low. below is a video of my SAI whine a while ago. https://vimeo.com/764610107

OK, thanks for the clarification, I hear it now. Not the normal engine whine but the slight high-pitch noise starting at about 1500rpm. It does sound a little like brake squeal. Not normal, also doesn't sound worrisome. Not SAI, that would be continuous on cold start at idle. It sounds like a slight metal-on-metal rub, as you said similar to brake squeal. Guess would be a loose pulley or a bearing. Is it the same issue you were having in Feb that seemed to be fixed by addressing the mufflers, or different? Did it start after you had the accessory work done? Since you have a 99, can you rev the engine at the throttle body and see if you can localize the sound? Running with the belt off would also help clarify.