Here is an interesting question from a Audio Masterclass visitor...
"How can I pick up the sound of the air displacement of a small stone falling down from 2 meters high? This is for a dance act, a dancer drops the stone. It will be in a live performance."
This is a tough one. Let's take it in stages...
Firstly, does the stone actually make any sound as it falls? Clearly it will make a sound when it hits the stage, but while falling?
Well yes, very probably it does. If you take a thin stick or twig and move it quickly through the air, it makes a swishing sound. This is the sound of air being displaced and forming complex currents around the stick.
The stone will undoubtedly do the same. But since it is moving much more slowly, the sound will be very quiet.
You could try attaching a miniature microphone to the stone. Let's ignore the cable for now.
This just might pick up the sound of the stone falling. But there would be a much higher level of noise caused by air moving quickly past the diaphragm.
My conclusion is sadly that either this sound is impossible to pick up and amplify, or it would take the entire science budget of a developed nation to find a way.
So it's impossible?
No... you could fake it. This is theater remember. It's all fake apart from the skills of the actors, dancers and everyone who contributes to the performance.
So, you could think hard and imagine what the sound of a falling stone is really like.
Think, think, think and think. Use all of your sound engineering experience and skill to conceptualize the sound, then lock yourself in the studio for a day so that you can recreate it.
Now, all that is necessary is for the sound to be triggered on cue. In my experience, this depends entirely on getting the dancer to realize how important it is to perform to the cue, in whatever form it takes, with absolute precision. Or the dancer can give the cue by incorporating a small but noticeable movement into the dance, just before the stone is dropped.
One last finesse...
You have applied your years of experience to determine what the sound of a falling stone should be like.
But the audience hasn't got a clue what it should be like! So actually, you have to come up with a sound that will be totally convincing to the audience, within their terms of reference and experience. They will have less than a second while the stone drops to fully assimilate the sight and sound presented to them.
So the sound you create has to be immediately convincing to the audience, rather than faithfully naturalistic.
Let us know how you get on!