Speaker noise from preamp circuit
As others have mentioned, that is not a very good circuit. Alas, we can't expect that just because we found it on the internet it will be a decent design.  I wold use a circuit more like this one.



Source: http://www.circuitstoday.com/transistor-intercom-circuit

This is billed as an "intercom circuit". But it is a good example of a circuit with sufficient stages of gain to take an electret microphone signal and boost it up to speaker level.  The switch (S2) will create a tone to signal the other end of the intercom.  You can omit S2 and C3 if you aren't using it for an intercom.