Weird Noises - Opinions? 2003 Manual (recordings)
 

Car: 2003 Honda Civic LX, Manual Transmission. 170k miles
Description of noises: metallic tumbling? Intermittent, somewhat random, mostly in lower gears as rpm changes

Is this a regular car sound or should I really have this checked?

Story: Car wouldn't pass smog this year, had to spend 2k to replace a cracked cat converter. After that, the car had sounds I didn't recognize, but I shrugged and said "This must be what a new cat sounds like" and I drove off.

An oil change later, the mechanic says "Don't you hear the weird sounds?" and I said, "That's totally the sounds it was making after YOU replaced the cat."

I moved, had another mechanic look at it, and replaced the alternator. Something about bearings tumbling around?? "No more sounds?" I asked this mechanic. "No more sounds," he assured. "Well, until you turn it on" he joked.

The sounds are 50% gone. I still hear them when shifting. Strangely, I hear them less when I shift early than when I shift normally. The higher the rpm, the more the sounds seem to occur.

Video 1: Sounds occur at about :23. Low speed, low gears, in a parking lot. I delayed shifting when the sound occurred to get a good recording. Probably in second gear.

Video 2: Sounds occur throughout the video, especially as I dip toward 60mph. Highway driving, 5th gear.

Appreciate any thoughts y'all have.

Re: Weird Noises - Opinions? 2003 Manual (recordings)
 

My first thought was it sounded like a heat shield rattling but it's kind of hard to tell in the video.

-Any idea where it's coming from? Front, back, left, right, underneath?
-Does it happen when revving the engine while not driving?

Re: Weird Noises - Opinions? 2003 Manual (recordings)
 

Re: Weird Noises - Opinions? 2003 Manual (recordings)
 

I can't hear squat.

You're trying to figure out some noise? WWSWD? (What Would Stevie Wonder Do?)