This might be obvious or expected to many, given that an an aluminum frame is basically a faraday cage, but I wanted to try it anyways since they would fit so neatly into the tube where the saddle is mounted in. But you cant find it or reach it to play a sound anymore, even if your just a few cm/inches away from it.
I just thought I shared this because I thought someone putting one there would surely test it, people might buy one with that intention… (I for one will just mount it in the bike with gaffer tape hoping it looks enough as if I fixed something, because all these holds look too obvious to be effective in a case of theft…)