Audacity Forum

And here all I want to do is to play a sound, then record it and find out the difference in volume from playback to recording.

Not according to your older posts.

If you want to know the "volume" difference between a signal that you're playing and one that you're recording you'll have to define exactly what you mean by "volume" (it's a poorly defined word in the audio world). Do you mean SPL-A? SPL-C? Perceived volume level? Digital Amplitude?

If you want to see which frequencies are strongest you can use the Analyze -> Plot Spectrum (which averages the signal and shows the amplitude of each frequency), or click the track name and select Spectrum to show you a spectrogram of the audio (which allows you to see how each frequency changes over time).

If you use the Spectrogram view, I highly recommend dragging the bottom edge of the track so it's as big as the Audacity window, you get more detail that way.