The sound source puts out sound waves, which are picked up by the microphone. The sound waves or audio signal is converted by a unit called ADC (Analog-to-Digital Converter). This digital information is then stored on a chip inside the recording device.
Digital information is broken down into zeros and ones and stored by the voice recorder device. When doing a digital voice playback, the unique 0 and 1 numbers are read by the Digital-to-Analog Converter or DAC. Once the device successfully reads the digital code, it is turned into sound which is processed by an amplifier.