http://www.robot-electronics.co.uk/acatalog/Ultrasonic_Rangers.html
I've used these for years, however I think you'll have trouble at a high density with crosstalk, even using narrow angle sensors. We've had six SRF08s running this week in cubby holes on an exhibition stand to trigger videos, and two or three splayed at 45 - 90 degrees on other occasions with out too much trouble. However running a couple side by side has given cross talk issues.
You'll probably have to cycle the sensors so the closer ones have a different duty cycle. You need a 65ms gap between different reads, so if you have all ten on a different duty cycle then it may be a little slow for very responsive audio.
You'll also need to ensure that you provide a separate power bus for the sensors, since the +5v pin may not provide enough.
Finally don't forget to look at EyesWeb, it only runs on windows and uses webcams, but is by all accounts very good. To boot it should be fairly easy to send OSC to Max from it.