As a start I’ve collected some possible ways for the user to generate/trigger sound:

1. Adjust channel by visitor’s location in room
2. Adjust volume by visitor’s location in room
3. Ambient light temperature affects effects/sound (windowed room or just affected by outside light)
4. Concealed ambience microphone
5. Huge mobile, objects on strings hanging from the ceiling, makes sound when visitors move through them (kinetic)
6. Microphone inside hard object, resonates on touch/hit
7. Microphone on floor
8. Punching balls -> microphones inside record hits
9. Punching balls -> sensors inside trigger sounds
10. Record time-lapse of people in room; generate sound from the pattern that is created
11. Several objects together make sound when moved/shaken
12. Single light source, shadows cast by visitors block out sounds based on which light sensors they trigger.
13. Single light source, shadows cast by visitors trigger effects.
14. Single light source, shadows cast by visitors triggers sound.
15. Sound triggered by touch (button/switch), effect/filter by ambient sound level
16. Sound triggered by touch (button/switch), effect/filter by location in room
17. Sound triggered by touch (button/switch), effect/filter by number of people
18. Tilt sensor in object, generates sound
19. Tilt sensor in pendulum, generates/tweaks sound
20. Video -> Movement triggers sound
21. Video -> Movement creates sound
22. Video tracking, when silhouettes overlap, triggers sound.
23. Visible ambience microphone
24. Vocal microphone

Then I’ve sorted them in the grid, like so: