I'm trying to get rid of exhaust drone. How long of a helmholtz chamber do I need?

The exhaust piping is 2.5" in diameter. Not too sure if it is relevant. So far, what I've been reading is that the drone occurs around 120Hz. I tried checking that on audacity and I got a different result where it seemingly was loudest at 130(ish)Hz. What I've got is that I need around 27-29 inches of branch piping on the exhaust... Could someone double check for me?

Here is the .wav and .mp3 file of the exhaust

Here is how the exhaust looks (not my car)

Thanks in advance!