555 timer circuit Light dependent tone generator

A very simple 555 timer circuit Light dependent tone generator is presented in this circuit diagram . What is so special at this 555 timer IC project ? this circuit use a LDR ( light dependent resistor ) to modify the frequency of the circuit . If the circuit is placed in a constant light the speaker will emit a sound with a constant frequency but we change the intensity of the light the circuit will generate a sound with a frequency that depends of light intensity .  If the tone generator circuit is placed in a dark place the circuit don’t emit any sound .

The 555 timer IC is connected in a astable mode and the oscillation time depends of the R1, R2, C1 components value . The speaker connected at the output terminals of the circuit must have a 8 ohms impedance and a power between 0.2-0.5 watts .
The transistor used in this tone generator circuit must be BD136, 2N2905 type or equivalent .