Normal voice we hear is from frequencies that are a combination of both high frequency and low frequency. Signal strength is not equal, will result in a different voice.
Operation of the circuit. When the power supply to IC1 by IC1 will work out the frequency produced by the pin 13 pin 3 is press the switch on left off. C to a value that will be connected to each circuit by the C makes the sound different.
Of the signal from pin 3 of IC1 is through R1 and VR1 is responsible for adjusting the strength of the signal will be expanded to IC2, which IC2 is IC amplifier with growing 1W signal that originates in the leg 5. The high frequency. And noise will be R3, C8 filter to ground the remaining signal is Retail Oil Link to C9 on the speakers.