that's right. the circuit is simple and works very fine. well you might replace the transistor and the components near it with a transformer, an increaser transformer, so you get a highter voltage for the input of the lm386, but it works better with a transitor.
another idea will be to replace the transitor and the speaker used as a microphone with an electret mic. but you will need 2 speakers and 2 mics and much more wire...........
so it is a good circuit as it is.