Sample Rate

As with bit depths, there are several different samplerates used for digital audio. While bit depth determines the accuracy of low level details, samplerate determines the accuracy of high frequency details.

Samplerate is actually the rate at which the digital audio is being processed, and where there are multiple files or audio streams being processed simultaneous (such as in a DAW or digial mixer) all the audio streams need to be at the same samplerate. For this reason, it’s best to choose a samplerate before recording begins, and avoid changing mid-project.

44.1 kHz

This is by far the most common samplerate, as it is the samplerate used by audio CDs.  Roughly speaking, the highest frequency that can be represented is exactly half the samplerate – so at 44.1kHz, the highest possible frequency is 22.05kHz. Seeing as most people cannot hear above 20kHz, this would seem like a good samplerate choice. The problem with this, however, is that the accuracy of those high freqeuencies is quite poor. The closer you get to the highest possible frequency, the worse the accuracy gets. As a result, the inaccuracies can sometimes be heard well below the highest frequency. For this reason, many plugins oversample their critical processing components – meaning the audio is internally converted to a higher samplerate so the highest frequencies can be processed with better accuracy.

48 kHz

This samplerate effectively has the same limitations as 44.1 kHz, except that it’s more commonly used for film and other visual media. This is because it syncronises better with visual frame rates (44.1 kHz doesn’t divide evenly into 24 frames).

96 kHz, 192kHz

Most modern professional digital audio systems can operate at higher frequencies than 44.1 kHz or 48 kHz. This allows audio to be captured and processed with much higher accuracy, especially at the highest frequencies. This usually results in a more open, natual sound. The trade-off is that much more processing power is required. Working at 96 kHz will half your capability compared to working at 48 kHz. That includes disk space (recording time), disk throughput (number of simultaneous tracks) and CPU/DSP power (number of compressors/EQs/effects). Working at 192 kHz cuts your capabilities in half again. Whether this trade-off is worthwhile for you depends on the kind of work you’re doing and your style of working. If you want to record the clearest, purest sound with a minimum of processing, high samplerates might be appropriate. On the other hand, if you want to do a lot of processing (especially if you regularly push your equipment to the limit) then you might prefer the higher capabilities of working at a regular samplerate.

Recording at these high samplerates also has an advantage for sound design and special effects. Because there is so much more high frequency detail captured, slowing down a high samplerate recording results in a much clearer sound than slowing down a sound recorded at 44.1 kHz or 48 kHz.

If you work at 96 kHz or 192 kHz, you might need to convert back down to 44.1 kHz or 48 kHz when preparing audio for distribution.

-Kim.

Advertisements
Comments are closed.
%d bloggers like this: