Bit Depth vs Bit Rate in Audio Recording

One Measures Speed and Both Indicate Quality

Teenage girl listening to music with headphones and mp3 player on living room sofa
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If you hear the digital audio terms bit depth and bit rate, you might think that these two similar sounding expressions mean exactly the same thing. It's easy to confuse them because they both begin with "bit," but they're actually two completely unique concepts.

You might need to know more about bit rate when choosing the best audio format for your portable device or when converting to the MP3 format with an audio converter tool or another program like iTunes.

Bit Rate in Audio Recording

Bit rate is a measurement expressed in kilobits per second (Kbps), which is thousands of bits per second. Kbps is a measure of bandwidth of data transmission equipment. It indicates the amount of data that flows in a given time across a network.

For example, a recording with a 320 kbps bit rate is processed at 320,000 bits per second.

Note: Bits per second can also be expressed in other units of measurement like megabits per second (Mbps) and gigabits per second (Gbps), but those are only used when the bits per second meet or exceed 1000 Kbps or 1000 Mbps..

In general, a high bit rate recording delivers better quality audio and takes up more space on your computer or mobile device. However, unless you have high-quality headphones or speakers, you aren't likely to notice the improved quality over one of a lower quality.

For instance, if you're listening over a standard pair of earbuds, you probably won't notice the difference between a 128 kbps file and a 320 kbps file.

You can read more about bit rate for some additional information, including how it relates to audio compression. 

Bit Depth

At first, bit depth might seem a complicated subject, but in its simplest form it is just a measure of how precisely a sound is represented in digital audio. The higher the bit depth, the more accurate the digital sound.

You've probably already encountered songs that come at a certain bit rate, either MP3 download services or streaming music sites, but rarely is much said about bit depth.

So, why bother to understand bit depth?

If you are going to digitize your collection of vinyl records or analog tapes in order to store them as high-quality digital audio files, then you need to know about bit depth. A higher bit depth gives a more detailed sound recording. A low bit depth causes quiet sounds to be lost.

For example, Compact Disc Digital Audio uses 16 bits per sample while Blu-ray Disc can use up to 24 bits for each sample.

This attribute influences how much detail you capture from the original analog recordings. Getting the bit depth right is also critical for keeping background signal interference at a minimum.

You can learn more about how bit depth affects sound quality here.