The plain fact is that It was chosen because it was technically feasible. It was the only available technology that could manage the data and bandwidth requirements. It was cost-effective to have these VCRs run at the same speeds as they would run at for video applications. Disk drives had the bandwidth but not the capacity for long recording time, so attention turned to video recorders. These were adapted to store audio samples by creating a pseudo-video waveform which would convey binary as black and white levels.
Such a recording can be made on a monochrome recorder, and these recording are made in two standards, lines at 60 Hz and lines at 50 Hz. Thus it is possible to find a frequency which is a common multiple of the two and is also suitable for use as a sampling rate. The allowable sampling rates in a pseudo-video system can be deduced by multiplying the field rate by the number of active lines in a field blanking lines cannot be used and again by the number of samples in a line.
Ah ha.. Digital audio stored on video recorders were to be sampled at But we know that tradition continues.. A few calculations were further explained as follows. The sampling rate of Even though CD has no video circuitry, the equipment used to make CD masters is video based and determines the sampling rate.
To the best of my knowledge, there are 50 lines of blanking per frame in a 50 Hz system 25 lines and 12 us per field. The field rate and structure used by the television standard is as follows for 60 Hz video: lines per field excluded the first 35 blanked lines.
This convention were later used for the CD format, due to equipment compatibility concerns the very first equipment used to produce CD masters used for CD replication was video based. Source: The Art of Sound Reproduction, p. Since human hearing range is roughly 20 Hz to 20, Hz, the sampling rate had to be greater than 40 kHz. In addition, signals must be low-pass filtered before sampling to avoid aliasing. While an ideal low-pass filter would perfectly pass frequencies below 20 kHz without attenuating them and perfectly cut off frequencies above 20 kHz, such an ideal filter is theoretically impossible it is noncausal , so in practice a transition band is necessary, where frequencies are partly attenuated.
The wider this transition band is, the easier and more economical it is to make an anti-aliasing filter. The It seems the hearinig limit for humans might be much higher than 20kHz if looked at from "dynamic" time resolution perspective rather than typical static sinusoidal waves.
Also interesting comments about the margin between 20kHz and 22 kHz for reconstruction filtering. Actually there's been quie interesting work from Peter Craven on time-domain optimized filtering which argues for at least 96kHz for hi-fi playback. A theorem called the Nyquist sampling theorem states that in order to sample a signal of X Hz without significant loss of quality, you need to sample at 2X the frequency.
The limit of human hearing is approximately 20kHz, which hence requires a sample rate of approximately 40Khz. This is why CDs are sampled at 44Khz. Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Learn more. Why do we choose Ask Question. Asked 7 years, 3 months ago. Active 3 years, 5 months ago. Viewed 18k times. Improve this question.
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