Scott D. Brown has created an elegant web interface for creating starkly beautiful circular spectrograms for uploaded audio files. The above one is the result of a 30-second recording I made of a fire alarm. The one below is of birdsong played in a bathroom (read for more details). Note how much less self-evidently rhythmic it is, and how the shading between frequencies is more varied and nuanced:
The next one, resembling a slice of a tree, is the sound of a train beginning to slow as it approaches a station. Looking at field recordings is a great way to listen to them. By observing how machines register to machines, you can find touchstones for your own attention.
And this final one, from the earliest of my recent spate of field recordings, is the phase shift of contrasting beeps from retail protection devices, plus occasional appearances of cashier pings and muffled human speech (read for details). You can actually see the phase shift as the distance between rhythmic elements grows smaller and then larger, round and round.
You can upload your own sounds to see what they sound like at spectrogram.scottbrown.co.nz. Brown is, per the URL, based in New Zealand.