Hi, by the looks of the picture, its from a book of circuits, or design ideas, and there is a layout diagram as well, I would hope that they have given you a parts list as well, that will tell you what resistance the loudspeaker is.
I think you want to know how loud the speaker will be, that depends on the physical size of the speaker, its resonant frequency range and the frequency that the oscillator is designed to run at.
its a book called Make : Electronics. It seemed like a great book but this is the second time that i have posted a circuit from it on this forum and both times the circuit was said to have bad design. So If you can offer me any other books that helped you learn I would be grateful for any help!
The greyed-out part of the circuit describes a terrible way to flash an LED. I cannot discern form where you got that picture, but many "instructables" and similar descriptions (such as YouTube) on the Internet are shockingly bad or even dangerous practice.
How would you design an LED flasher circuit?
A circuit that old is relying on the probably rather high ESR of that 2.2uF capacitor to not damage the LED. Or not so quickly that it immediately fails.
According to the datasheet, the forward voltage is more like 1V. However, you can't just use the numbers to calculate power, because that is an impulse, a capacitive discharge into the speaker.
Umm.. I understand what you mean by an impulse. But how would you calculate the power then if you couldn’t use numbers? Trial and error?