hmmm there are several components in that circuit not connected to anything . . .
there also appears to be an redundant switch . . .
it looks as if when both switches are closed, the speaker emits a noise for the time it takes the capacitor to charge.
and oddly the + end of the battery is connected to ground . . . definitely not normal for today.
one of the components looks like a microphone . . . making sounds into it can fluctuate the voltage, making the speaker create a similar sound . . .
i bet its an old telephone circuit!!!