Stretching and squeezing sounds is a great way to sculpt weird and wonderful effects and really make your tracks stand out. This is done with a technique known as sample rate conversion. In this article we’ll explain what it is and how to use it.
Sample rate conversion is simply the art of playing back the samples stored in an audio file at a variable rate. By simply changing the rate that samples are played back, a simple tap on a table can become a massive booming bass sound. Crinkling tinfoil can be transformed into shimmering cymbals. Sounds awesome, huh? The best part is that all this can be achieved by the click of a button and some quick bouncing down.
What is a sample rate? Audio files are made up hundreds of thousands of samples (or pieces of info) and the rate their played through dictates the pitch, length and file size of the audio. For example, the industry standard sample rate is 44,100 samples for every second of data (also known as CD quality audio). This means that in a 10 second-long sample, there’s 441,00 samples or pieces of info stored. If you play that sample at 44,100 samples per second (44.1kHz), it will play back at normal speed. When you make the sample rate faster the pitch goes up and the file size decreases and the opposite applies when you slow down the sample rate. This happens because you are playing the samples either quicker or slower than they were originally stored so the wavelengths of the sounds are shorter or longer.
To find out more about the process of changing the sample rate in each of the major software types, head to Pro Audio Files. If you’re a Logic Pro user then Mode Audio have a great step by step guide.