What Is Nyquist's Law?

"A picture is worth a thousand words. " Is there a saying like that? You can do better than that if you're an analog signal you can speak for yourself! But how? With Nyquist's Law, of course. It's a formula stating that to accurately represent an analog signal in a digital format, two samples per cycle are sufficient. In other words, your sampling rate must be at least twice the maximum frequency of your analog signal to extract all bandwidth information and accurately represent analog signals in a digital format. Sampling rates slightly exceeding the suggested frequency level lead to imprecision in filters and other analog-to-digital conversion components. It's time to get down to the nitty-gritty of sound, how it travels, what it looks like, and how we can manipulate it. First things first, let's talk about transducers. Transducers are devices that convert acoustic energy into electrical energy. These are primarily microphones but can also be speakers or other instruments. Once the sound is converted into electrical signals, we need to convert those signals into a digital representation through an analog-to-digital converter. The more times we sample our waveform per second, the number of times we mark each point on that waveform, the more accurately we'll be able to reconstruct it later. That's why CDs sample at 44,100 Hz! Nyquist's law states that a digital signal can be perfectly reconstructed from a sample if the sampling rate exceeds the highest frequency contained in that signal. The term "law" is somewhat misleading, as it was never intended to be a law of nature or physics but rather a guideline for how engineers should design circuits to process analog signals. Nyquist's law is currently the standard for pulse code modulation (PCM) in Japan and North America for converting analog sounds into digital formats. For example, a 2 kHz voice signal is sampled 4,000 times per second, and each sample is transformed into an 8-bit number to produce a 64 Kbps data stream.