What Is Bit Depth?

Learn about this indication of audio quality

In digital audio, a value called bit depth describes the resolution of the sound data that is captured and stored in an audio file. A higher audio bit depth indicates a more detailed sound recording.

Similarly, for image and video files, bit depth is used to determine the resolution of a picture. The higher the bit depth — 24 bit versus 16 bit, for example — the better the image.

Bit Depth vs. Bit Rate

Bit depth is often confused with bit rate, but they are different. Bit rate, which is measured in kilobits per second, is the data throughput per second when sound is played back, not the resolution of each discrete sample that makes up the audio waveform.

Bit depth is sometimes referred to as the sample format or audio resolution.

For more information about the difference between bit rate and bit depth, check out our summary of these two concepts.

Bit Depth and Sound Quality

The unit of measure for bit depth is binary digits (bits); for every 1-bit increase, the accuracy doubles. The bit range is an important integer that determines how good a recording sounds.

If the bit depth is too low, the recording is not accurate, and a lot of quiet sounds are lost. MP3s stored in your music library that have been converted from analog audio to digital audio signals using pulse code modulation (PCM) with a high bit depth contain a wider spectrum of frequencies than ones encoded with low bit depths.

The high-bit-depth recordings are far more accurate on playback, particularly in areas of songs that contain quiet harmonics. Using too low a bit depth can lead to lost frequencies and low-quality recordings.

Bit depth is only relevant in the scope of a PCM signal. Lossy compression audio formats do not have bit depths.

Bit Depth and Dynamic Range

Having the right bit depth is a critical aspect to consider to reduce the amount of background noise. Every recording has a degree of signal interference called the noise floor, which is kept to a minimum with a sufficiently high bit depth. This phenomenon occurs because the dynamic range — the difference between the loudest and quietest sounds — is much higher than the noise floor, allowing the difference to keep noise to a minimum.

Bit depth also determines how loud a recording can be. For every 1-bit increase, the dynamic range increases by about 6 decibels. Audio CD formats use a bit depth of 16, which equates to 96 dB of dynamic range. If DVD or Blu-ray is used, the sound quality is higher because the bit depth is 24, which gives 144 dB of dynamic range.

  • How to check bit depth for audio?

    Using the popular multimedia app VLC, open your file then select Tools > Codec Information. Bit depth is displayed in the Bits per sample section.

  • How do I change bit depth in an image?

    There are quite a few free image resizers that change bit depth in photos. Go to Settings to change the resolution of an image by increasing or decreasing pixels (px) or inches\cm.

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