What is Nyquist Bit Rate 1

The sampling rate - groping for the best sound

When it comes to digital music and sound effects, the sampling rate plays an important role. This applies to CDs as well as to file formats such as MP3 and network players. The specified values ​​for the height or frequency of the removal rate differ significantly from one another. An important reference value is 44.1 kHz. We explain why this is so.

What the sampling rate is all about

For example, so that a voice or a guitar riff can be stored on a CD or hard drive, the analog audio signal must be digitized. To do this, the analog signal in constant time intervals (Discrete time) samples (in English: Samples) taken. These are used to convert the recorded information into a code. If the signal is digital - for example in MP3 format - it can also be converted back into an analog signal in order to make the membrane of a loudspeaker vibrate. The frequency of these samples or samples is indicated by the sampling rate. In general, the more samples there are, the more detailed the sound can be digitally reproduced.

A CD supports signals that have been digitized with a sampling rate of 44,100 Hz or 44.1 kHz. Corresponding 44,100 samples per second. Of course, this frequency was not determined by chance. Such a resolution takes into account the maximum audible audio frequency of about 20 kHz and an important rule of data processing: the Nyquist-Shannon theorem. From this it can be deduced that the sampling frequency must be at least twice as high as the highest frequency of the signal to be digitized. So if the highest tones that we can hear vibrate at 20 kHz, according to this theorem, the sampling frequency must be at least 40 kHz in order to really digitize and decode all tones correctly. Otherwise the digitized signal can only be incorrectly converted into an analogue one.

This video explains the theorem in more detail:

44.1 kHz is not the end of the story

The development of the sampling rate did not stop at 44.1 kHz. Modern data carriers and transmission methods now make it possible to process significantly higher amounts of data. Loss-free formats such as FLAC or high-resolution multi-channel standards exceed this value many times over.

Dolby TrueHD, for example, also supports very high sampling rates. Significantly finer digitized signals can therefore be processed. In addition, audio masters can use better reconstruction and anti-aliasing filters.

The sample rate is not the only measure: the bit depth

While the sampling rate describes the frequency of the samples, the bit depth indicates how many bits are used per sample. In other words: the bit depth tells you how precise or how high a resolution each individual sample is. The amplitude or dynamic range of the analog signal at the time of the sample is determined, i.e. the range between the weakest and the strongest sound pressure level. Each sample on a CD has a depth of 16 bits, whereby this value is also exceeded with modern digital standards. Dolby TrueHD reaches 24 bit.

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Conclusion: The sampling rate as the currency for digital sound formats

  • The sampling rate indicates how often signal samples are taken from an analog signal.
  • The Nyquist-Shannon theorem states that for digitization to be true to the original, the sampling rate must be at least twice as high as the highest analog frequency.
  • CDs support sampling rates up to 44.1 kHz. Modern formats, on the other hand, can reproduce 96 kHz and beyond.
  • The bit depth indicates how the individual samples are resolved and influences the digitized dynamic range.
  • While the samples on a CD have a resolution of 16 bits, Dolby TrueHD, for example, achieves 24 bits.
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