I was playing with this last night. If a resistor is used with the LED, it obviously can't oscillate very fast because of the discharge delay, so if you want higher frequencies, there has to be a low collector (load) resistance.
With ear buds as the load, the sound of the pulses remind me of the pulses from a tens unit. I bet this circuit could drive a small HV transformer.
I am also wondering about using it as a driver for an ultrasonic transducer. Capacitor type matters too. I was using 10uF ceramic caps last night and the audio tone would change noticeably by breathing on the capacitor. Gave me a new appreciation for capacitor thermal stability for sure.
I lost most of them already, but last night I was thinking of all sorts of things to do with a circuit like this. I wonder if it could ring a coax stub and generate audible AM at the stub frequency or if the rise time would need to be faster.