Bit Depth vs. Bit Rate in Audio Recording

One measures speed; both indicate quality

The digital audio terms bit depth and bit rate are so similar that many people assume they mean the same thing. It's easy to confuse them, but they're two different concepts.

Bit Depth
  • Determines audio fidelity.

  • Controls how much data in audio files.

  • Impacts clarity and detail.

Bit Rate
  • Measure of bandwidth in audio files.

  • Impacts playback quality.

  • Factor in determining file size.

You might need to know 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 such as iTunes.

Bit depth becomes important when you are digitizing your analog music collection or you need the highest possible sound quality.

Bit Depth vs Bit Rate

Bit Rate in Audio Recording

What it Can Do
  • Sets the overall number of bits of data, determining quality.

  • Can control the size of your files.

  • Bit rate is a measure of bandwidth, meaning you'll need a connection to support it.

What it Can't Do
  • Add detail to a lower quality recording or rip.

  • Determine how much data is already in the file.

Bit rate is a measurement expressed in kilobits per second (Kbps), which is thousands of bits per second. Kbps is a measure of the 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.

Bit rate 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 lower quality.

For example, 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 additional information, including how it relates to audio compression. 

Bit Depth

What it Can Do
  • Control how accurate your recording is.

  • Determine the level of detail in the recording.

  • Dictates how much data there is describing the audio.

What it Can't Do
  • Add detail to your file that wasn't already there.

  • Control the amount of bandwidth needed to play a file.

At first, bit depth might seem a complicated subject. In its simplest form, it is 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 from either MP3 download services or streaming music sites, but rarely is much said about bit depth. However, if you are going to digitize your collection of vinyl records or analog tapes to store them as high-quality digital audio files, 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.

The measurement for bit depth is bits. For each 1-bit increase, the accuracy of the recording doubles. The higher the bit depth, the better the recording sounds.

Audio CDs use 16 bits per sample, while Blu-ray Discs and DVDs use 24 bits for each sample. The sound quality achievable on the Blu-ray Disc or DVD is significantly higher than can be achieved on an audio CD.

This attribute influences how much detail you capture from the original recordings. Getting the bit depth right is also critical for keeping background signal interference at a minimum, as well as affecting the volume of your recordings.