Sample Rate is, more or less a part of the analogue to digital conversion process. The sample rate is represented by a number such as 44.1, 48, or 96, and represents how many thousands of snapshots a computer takes of an incoming analogue signal to turn it into a digital signal. The best analogy I heard for understanding sample rate is thinking of it like a screen’s refresh rate. A screen creates motion by flashing dozens of still images in rapid succession, and similarly a computer grabs a still or a “sample” of a sound signal multiple times a second to recreate the waveform as a digital signal.
The blue line in this graph represents the true analogue sound wave, and as it passes into an ADC (analogue to digital converter) the computer takes samples (represented by the yellow diamonds) of the amplitude of the waveform at timed intervals. The computer can then metaphorically connect the dots to create a representation of the waveform, as seen in the graph below.
The more samples taken of a waveform will create a more accurate representation. Typical CD sample rate is 44.1, which means 44,100 samples per second. You’ll see higher sample rates with professional sound equipment that measure 48, 96, or even higher rates. Though higher rates will inevitably sound better, they will also take up more storage space in your computer to hold all those added samples.
As a well-rounded sound engineer, it’s important to become familiar with something called the Nyquist Theorem. This theory, hypothesized by Mr.Nyquist none-the-less, states that for an accurate representation of a sound there needs to be at least 2 samples per cycle. With this information we can deduce that since the highest frequency humans can hear is 20khz, then the lowest sample rate we’ll want is 40khz. And this is how the CD standard sample rate of 44.1khz makes sense (the extra 4.1 were added for a little headroom). In most applications you’ll only need 44.1khz or 48khz, but there are specific use-cases where higher sample rates are required.
The other half of analogue to digital conversion is Bit Depth, which we will cover in depth in another post.
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