If you read the Wikipedia article you linked to, you'll discover that there are different types of microphone.
The problem is you need lots of gain and a high input impedance for an electret mic. Here's a simple circuit that will drive a small relay from an electret mic, I haven't tested it but it should work.
Tr1 is an emitter follower which has a gain of 1 and a high input impedance.
Tr2 is a common emitter amplifier which has lots of gain.
Tr3 is a precision rectifier which rejects half of the waveform. D1, R9 and R1 set the base voltage just below Tr3's turn on voltage.
C4 and R11 form a low pass filter which keeps the output switch on in-between troughs.
T4 is another common emitter amplifier which switches the relay.
R12 provides positive feedback which adds hysteresis making the circuit more stable.
R3 alters the sensitivity of the circuit.
It would be easier to build the circuit using ICs such as an op-amp and comparator but I was bored.