I have seen this project in other places, so I was excited to try it. Unfortunately, I never got it to work, even after several prototypes.
I tried it first with Dixie cups. I used two different kinds of headphones, and hooked it up to two different devices. If it amplified the music, I couldn’t tell it at all.
So I tried larger, plastic cups thinking that the sound would bounce off the hard plastic better than paper, and that the larger cup would help. I couldn’t tell any difference.
Does this mean it’s a “bad” project? Absolutely not! It’s a great project to take to your makerspace students and say “I couldn’t get this to work… can you?” And see what they come up with. Not everything may work the first time in a makerspace, but we’re building our persistence muscles as we learn, which is valuable time spent.