For this exercise, the main constraint is the auditory element.
Freewrite for ten or twenty minutes (at least), focused only on the sense of sound.
As you write, really get into the feeling of the sound.
You might listen to music and write the way a song feels.
You might say nothing about the music, instrumentation, or lyrics. You might instead prioritize how you feel as you deeply experience it.
Imagine sounds. The way your characters make sound. Spend time with them gearing into only the sense of sound. How would you experience them if all you could do was hear?
The sound of their voice when they talk — what emotional range is most common for them? How do they sound different when frustrated? Enraged? Relaxed? Happy?
Do their clothes make sound? Their footsteps — what do they sound like? Are they generally noisy or quiet individuals?
The different settings — how do they affect the sounds of what happens within them? What sounds are common to find in this area? Birds or other wildlife? Rats or scurrying rodents? Traffic of any kind? The weather — what sounds does it make?
Get synesthetic. Don’t hold back if you find yourself experiencing and describing the smell of a sound. By sticking only to a single sense, you are bound to run out of shorthand descriptors for the way something literally can be described to sound.
It’s perfectly acceptable, definitely welcome to become synesthetic, wacky with your descriptions.
the pad of her shoes
the smoke of his boots on the carpet
the impotent chirp of his sandals on the flapping vinyl
floor of the palapa
Let it be whatever it is. Who cares what you write when you are doing a freewriting exercise. It’s a time when you are to allow no judgment — only creation. Only perception.
Just do it and get into your sense of sound. Find new ways of describing things. If, when you are finished, you read back through and find a couple of descriptions feel worth hanging onto, cut them and paste them in whatever folder you use to collect clever phrases.
The more important side of the exercise is this: it’s primarily about getting exercise, not about keeping what you write.
Let it come and go and see what emerges — in you — as you write.