What Is Bit Depth?

Bit Depth Definition and Description

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In digital audio, there has to be a certain value set for describing the resolution of the sound data (samples) that is to be captured and stored in an audio file. This attribute is called bit depth.

Similarly, for image and video files, this measurement range is also used to determine the resolution of a picture. The higher the bit depth (e.g. 16 bit versus 24 bit) the better the image will be.

This attribute is exactly the same for digital audio and thus a higher audio bit depth will give a much more detailed sound recording.

Bit depth can often be confused with bit rate, but they are very different. Bit Rate (measured in Kbps) is the data throughput per second when sound is played back, and is not the resolution of each discrete sample that makes up the audio waveform. See Bit Depth vs Bit Rate for more information.

Note: Bit depth is sometimes referred to as the sample format, audio resolution, or word length.

More Information on Bit Depth

The unit of measure for bit depth is in binary digits (bits) and for every 1-bit increase, the accuracy is doubled. This bit range is an important integer that determines how good a recording (a piece of music for example) sounds.

If the bit depth is too low, the recording will not be very accurate and a lot of quiet sounds can be lost. For the songs that make up your digital music library, MP3s that have been encoded from a PCM audio format (usually WAV) with a high bit depth will contain a wider spectrum of frequencies when compared to ones that have been encoded from original PCM files with low bit depths.

In theory they will therefore be far more accurate on playback. As previously explained, bit depth is especially critical when dealing with quiet harmonics in songs - using too low a bit depth can lead to lost frequencies.

Bit depth is only relevant when in the scope of a PCM signal, which is why lossy compression audio formats do not have bit depths.

Other Ways Bit Depth Affects Sound Quality

Making sure your digital audio files don't suffer from clipping is important, but having the right bit depth is also a critical aspect to consider in order to reduce the amount of background noise.

Every recording has a degree of signal interference (called the noise floor) which can be kept to a minimum if using a high enough bit depth. This is because the dynamic range (the difference between the loudness and quietest sounds) will be much higher than the noise floor, allowing the difference to keep noise at a minimum.

Bit depth also determines how loud a recording will be. For every 1 bit increase, there is about 6 dB of added dynamic range. The most popular media format in use today is the audio CD format, which uses 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 used is 24, which gives 144 dB of dynamic range.

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