Sample Rate and Bit Depth: How Do They Affect Audio Quality?

If you’ve recorded audio via a DAW or digital recorder before, you’ve probably come across terms like sample rate and bit depth. These are the most important factors when it comes to determining the detail in which sound is recorded. The sample rate determines the frequency range of the recording, while the bit depth controls the dynamic range. Read on to find out what settings you should use to get the best sound for your productions.
Sample Rate and Bit Depth: How Do They Affect Audio Quality?

Sample Rate: Audio Pixels

The sample rate of a digital signal can be best compared with the amount of pixels in a digital photo. Much like digital images, digital sound is made up of extremely tiny pieces that are called pixels in photographs, and samples in sound. Sample rates are expressed in kilohertz (kHz) and as you may know, the standard sample rate for a CD is 44.1 kHz, which means each second of recording consists of 44,100 samples. Unlike photos, you won’t see or hear any blurry blocks, if the quality drops, the sound mainly get duller.

Why 44.1 kHz?

Near the end of the ‘70s, Sony and Philips decided to go with the 44.1 kHz sample rate as the default for their digital audio devices. The number may look random but can actually be logically explained: to capture and record any highest frequency, the sample rate must be at least twice as high. If the sample rate is lower, ultra-high frequencies might be incorrectly interpreted by the converters, an occurrence called ‘aliasing’. Since human hearing is theoretically capable of perceiving a 20 Hz to 20,000 Hz frequency range, the sample rate has to be at least 40 kHz. The spare 4.1 kHz was thrown in as a buffer for low-pass filters used to prevent any aliasing above the 20 kHz line.

Smack My Bits Up

So the sample rate tells us how many pieces a recording is made up of. The bit depth, other the other hand, tells us how many different pieces there are. In other words, the bit depth determines how many steps there are between the quietest and the loudest sample. You’ll find that most audio interfaces and DAWs offer 16 bits or 24 bits. When you make extremely low-volume recordings at a low bit-depth, chances are that the softest bits will fade out in the static, and you might even get some distortion.

99 Problems But a Bit Ain’t One

The standard bit-depth for CDs is 16-bit and a dynamic range of 96 dB. That’s already a huge improvement compared to tape (+/- 80 dB), but professional studios still tend to go with 24 bits. The 144 dB dynamic range that results in makes sure you needn’t worry about any static noise the digital device adds to the signal. Better yet, it’s best to record at low volume and mix at a louder one.