Sample Rate is the number of times the audio is captured per second.
It is to audio what frame-rate (Frames Per Second) is to video.
Sample Rate values are typically written in kHz (kiloHertz).
Sample Rates come in 'bands' and common examples include:
- Single-band - 44.1kHz & 48kHz
- Dual-band - 88.2kHz & 96kHz
- Quad-band - 176.4kHz & 192 kHz
For example, when recording using a sample rate of 48kHz. 48000 (forty-eight thousand) samples are being captured each second by your audio recording device.
As you increase the sample rate, you capture more samples of the incoming audio signal each second.
The maximum frequency that can be captured correctly by a recording device1 is limited by the sample rate the device is set to.
There is quite a simple rule2 to this:
Sample rate ÷ 2 = maximum frequency that can be correctly captured
This means, when using a sample rate of 48kHz, we can capture audio frequencies up to 24kHz.
The range of human hearing is from around 20Hz to 20kHz (though we lose the ability to hear the higher frequencies as we get older) so sample rates of 44.1 & 48kHz are more than capable of capturing the full range of the human audible spectrum.
As such, the vast majority of digital music available by typical distribution methods (streaming on Spotify/Apple Music, CDs) is at a 44.1kHz sample rate, audio for film tends to be at 48kHz3.
What's the point of higher Sample Rate options then?
Since sample rates of 44.1/48kHz allow us to capture frequencies spanning the full range of human hearing, you wonder what the purpose of higher sample rate options is.
There is debate in the audio community regarding the value (or lack of) of using higher sample rates for situations that don't fall into the above categories (i.e. for general recording purposes). We won't get into that here...
Bit Depth is the number of “bits” captured in each sample per second.
As bit depth changes, so does the dynamic range. Dynamic range is the difference between the lowest and highest volume of a signal that can be recorded. As you increase bit depth, you expand the threshold of what can be heard and recorded by your recording software. However, the maximum range of human hearing typically does not exceed 120 dB.
Common Bit Depths: 16, 24, 32-bit float
Buffer Size is the amount of time allowed for your computer to process the audio of your sound card or audio interface.
This applies when experiencing latency, which is a delay in processing audio in real-time. You can reduce your buffer size to reduce latency but this can result in a higher burden on your computer that can cause glitchy audio or drop-outs.
This can often be fixed by increasing your buffer size in the audio preferences of your DAW or driver control panel.
When introducing more audio tracks to your session, you may need a larger buffer size to accurately record the signal with no distortion and limited latency. Increasing the buffer size will allow more time for the audio to be captured without distortion.
It is important to find the appropriate buffer size for your session as this can vary depending on the number of tracks, plug-ins, audio files etc...
1 This assumes that neither the analogue circuitry nor the analogue to digital converter, in the input stage have any filtering to cut out or attenuate higher frequencies.
2 This rule is known as the Nyquist Theorem.
3 Audio for film tends to be recorded at either 48kHz or a higher multiple of 48kHz for better synchronisation against film frame rates.