People strap cameras under their cars and have good results in seeing what's happening.  And if you posted a video of the noise somebody might recognize it.  It's weird how the ear and brain can work together.  "Banging noise" covers a lot of spectrum.

They make tools specifically for finding noises but the reviews are really mixed

I had a mechanic that used remote listening devices like the one on Amazon and he did a great job of finding a rattle with it. I'm a bit surprised that they go for $100 or so as I thought they would be pricier. I was going to just live with all the noises from my Z but this give me a whole lot more I can tinker with.