Never got around to the ANR kit for my 13.4's, but here's something cheap that might be worth a try. Ear plugs. Stick a pair in your ears, then crank up the volume on the headset to compensate.
Result, less background noise, same perceived audio. Your mileage may vary, and it might be antisocial for the instructor if present.
Another idea I've pondered is good (passive) noise isolating in-ear headphones, with the headset over the top. But honestly you should be fine with regular 13.4's in a C150, you'll find with practice you'll get better at decoding the babble.