Speech/voice recognition: Digitizing voice/audio signal

In the previous "Audio Signal Properties" we have studied the electrical properties of audio signal. In the world of digital electronics, the semiconductor logic and processing devices does not compute without digitizing the analog signal. A semiconductor device called analog to digital converter is used to convert linearly varying analog-flow into multi-bit digital binary numbers of where constant output voltage of 5V/3.3V is binary number 1 and zero voltage is binary number 0, representing amplitude quantity of analog signal. To give an example, a 6 volt measuring analog signal can have 8-bit binary output of ‘00000110’. I will not discuss here how ADC circuit of semiconductor transistor/MOSFETs convert analog signal into digital. Instead we focus on aspects of quantizing, sampling, and digital representation of analog data. Let’s take a sample single cycle of an audio signal which looks like as shown in the Pic number-1 below. Due to limitations of present analog to digital converters, you can not convert every instant of analog signal into digital signal. Some instance or sample of analog signal is taken in such a periodic way that the space between samples is decided in such a way that the difference in amplitude of adjacent samples is very minimal. That rate...