I'm learning to recognise the different buzzings of the bees.
The collective buzz of worker bees flying, the colonies humming within their hives, and the individual buzzings of bees that find themselves on the wrong side of the house windows, all combine to provide the background noise round here for most of the year. So that's my benchmark as "normal" buzzing. From there, I am beginning to pick up variations from it. For instance, if a particularly loud, low pitched insect hurtles past my ear on its way to or from the hive, I know it's probably a drone rather than a worker. And more dramatically, the sound of a swarm in flight is recognisable by its LOUDNESS.
I've heard queens piping. That is a distinctive sound, like a tiny trumpet. Sometimes you can't see the queen, but you can hear her, and so work out where she is until at last your eye can find her in that sea of bees.
Then there are different things to learn by listening to the bees buzzing as a colony. Their state of "mind". Whether the queen is in residence. Whether it might be a good idea to close up the hive and retreat...
That backdrop of sound has lessened now that the weather is cold and the days are short. However, a different experience is to put a stethoscope to the wall of the hive and eavesdrop from outside. Clicking, scuffling, humming.