In audio recording, bit depth can affect the overall quality of your resulting audio. Using a bit depth of 16 is almost always sufficient for home recording, and in some cases a bit depth of 24 will give a slight improvement.
The most important effect of bit depth is that it determines the dynamic range possible in a recording. Low bit depths can fail to record sounds of lower intensity (sounds that aren’t loud enough).
In order to gain a full understanding of why this happens, we must start at the beginning, with the process of recording itself.
Audio Bit Depth Defined
Bit depth in audio recording is just the number of bits of information in each audio sample.
Let’s unpack that definition a bit (pun intended).
What is a bit?
A bit of information is the most basic unit of information in computing. You often hear computer language referred to as “1’s and 0’s.”
Well a single bit can either be a 1 or a 0. So a single bit can only convey one of two values.
However, two bits can convey one of four values (00, 01, 10 and 11), three bits can convey eight values and in general X bits can convey 2^X values.
In audio, you usually see 4-bit, 8-bit, 16-bit and 24-bit options (maybe 32-bit).
Even though 8-bits only has 4 additional bits of information, it conveys 16 times the information of 4-bits. Each additional bit makes a huge difference, it doubles the amount of information that can be stored in an audio recording.
What is a sample?
In my article explaining sample rate, I describe the process of sampling an electrical signal that carries audio information.
The crash course is this:
- Raw audio (compressed air waves) is sent to a microphone
- The waves hit a magnet in the microphone which is surrounded with electrical wiring
- The magnet then moves/vibrates creating and electrical current in those wires
- The electrical current moves to a sampling device (usually an audio interface)
- The audio interface takes samples of the electrical current at a specified rate (typically 44,100 samples per second)
Each of the 44,100 samples taken of the electrical current is like a photo being taken. It captures a moment in time and records the data.
The number of bits being used to record that data determines the amount of information and ultimately the accuracy of that information.
Audio bit depth in context
So let’s bring it all together.
When raw audio is converted into an electrical signal (typically by way of a microphone), the signal carries detailed information about that original audio.
A tool takes very fast snapshots (also called samples) of the current state of the electrical signal. Each snapshot will carry an amount of information correlated with the bit depth of the recording.
If the bit depth is 4, then each snapshot/sample will carry 4 bits of information. If the bit depth is 16, then each snapshot/sample will carry 16 bits of information and so on.
A quick analogy (audio vs. video)
I like to think about audio samples as photos. In the same way that our eyes are unable to differentiate each individual frame/photo that makes up a motion picture, our ears are unable to differentiate each individual audio snapshot that makes up an auditory recording.
And we can actually take the analogy a little bit further to understand bit depth better.
Bit depth in an audio sample is a lot like visual resolution in a photograph.
Imagine you have a photo resolution of 4×4. That photo will carry 16 pieces of information about the photo, essentially 16 dots with a specified color. If we could increase that resolution to 8×8, then the photo would have 64 pieces of information and the photo would look clearer.
Likewise, the more bits used to take an audio sample, the clearer the audio will sound in the final recording.
Practical Use of Bit Depth (Dynamic Range)
It’s a bit easier to understand how photo resolution affects a video than how bit depth affects audio recordings. My grasping of the process is still a bit blurry in certain spots. But I’ll do my best to convey everything as I currently understand it.
What information is in an audio sample?
Well an electrical signal has an intensity. The audio electrical signal increases and decreases in intensity as it passes through the wire.
The audio sample/snapshot of that electrical signal is basically just measuring the signal’s intensity at a moment in time.
You could think of it like an ocean wave. Different spots on the wave have different heights. If you measure the height of the wave over time that would give you a measurement much like that of an electrical signal.
So the sample carries information about amplitude or intensity of the electrical signal at a moment in time.
Amplitude/Intensity is partly a measurement of sound volume
One aspect of that audio sample measurement is the volume of the original sound.
Remember, the number of bits in your audio sample determines the amount of information that can be held in each sample. And part of the information is the amplitude or intensity of the electrical signal.
So using a bit depth of 4 will be able to tell you the amplitude of the signal with some amount of detail. And using a bit depth of 8 will be able to tell your the amplitude with significantly more detail.
Bit Depth Determines Dynamic Range
The bird’s eye (or bird’s ear?) view of this situation is that higher bit depth allows your recording to record information about quieter sounds.
Lower bit depths carry less information and therefore will only be able to take an audio snapshot of the loudest, most pronounced aspects of the electrical wave. But any audio information below a certain threshold (meaning any sounds below a certain volume) will not be recorded in the audio sample. Therefore those quieter sounds will not make it to the final recording.
A more accurate definition of dynamic range
So dynamic range is slightly more complicated than just saying “sounds under a volume threshold won’t be recorded”
More accurately, bit depth determines the sound intensity range, in decibels, that can be recorded.
|Bit Depth||Dynamic Range|
Let’s reference the table above. A bit depth of 4 has a dynamic range of 24 dB.
What does this mean for recording exactly?
Well it means that your audio samples will be able to capture the loudest sounds and any sounds that are no more than 24 dB quieter than the loudest sound.
In practice, at very low bit depths, a lot of the recording can come across as static.
So higher bit depths will capture more of the original audio sounds and will sound much clearer overall.
What Bit Depth Should I Use For Recording?
In general a bit depth of 16 is adequate in almost every circumstance, and a bit depth of 24 should always be enough.
Most mass produced music playback devices use a playback bit depth of 16.
However, when editing/mixing your recordings, a bit depth of 24 can offer more flexibility and sometimes even make a difference in clarity of the final product.
One more small thing to be aware of is that higher bit depths will result in bigger file sizes. With today’s cheaper storage, this probably shouldn’t matter, but I think it’s useful to be aware of this.
If you find that you’re running out of storage space and can’t afford to get more, you may consider lowering your bit depth to save space. This also applies to sample rate.
In the process of recording audio, bit depth determines the amount of information that can be stored in an audio sample.
In practice, it determines the dynamic range that can be captured in a recording, which can affect the overall clarity and accuracy of your recordings.
I recommend a bit depth of either 16 or 24 for your home recordings. Both will be sufficient and in certain scenarios you may experience slightly improved results with a bit depth of 24.