Recommendations for SINAD equipment
So, you've got the audio signal in digital on your PC.

Analyze that digitally; you don't need any measurement equipment to do that.

On the contrary: Measuring properties of the analog audio signal is highly undesirable, because you'd be including the sound card of your laptop in your measurement, but you probably don't care about that even remotely. If you actually wanted to know the properties of your sound card, then you'd need to separately measure that – but you'd do that with a "clean" test signal generated by your PC, not something received over a noise system.