Yeah, sound is better than light for that kind of test - but also still not good; because there are many things that block sound but don’t block wifi, and visa versa. (eg. a well insulated double-glazed window is good vs sound, but doesn’t stop any wifi; and a metal mesh can block wifi while stopping very little sound.)

I remember one time I spent ages trying to debug a wifi problem with my laptop. I was messing around with computer settings and router settings for ages trying to work out why my wifi had stopped working. But in the end, I found that it was entirely due to where I was sitting. I sitting in front of my desktop computer’s very large monitor, and the router directly behind the monitor on a shelf in the room next door. The monitor was blocking the wifi. If I move the laptop or the monitor, it worked fine.