A 44.1 kHz digital sampling rate is limited to frequencies no higher than half that, 22.05 kHz ( due to Nyquist rate issues ), which is barely more than human hearing's upper limit ( and some people can hear frequencies aboe 22.05 kHz ).
32.
In signal processing, "'undersampling "'or "'bandpass sampling "'is a technique where one samples a bandpass-filtered signal at a sample rate below its Nyquist rate ( twice the upper cutoff frequency ), but is still able to reconstruct the signal.
33.
Nyquist's famous 1928 paper was a study on how many pulses ( code elements ) could be transmitted per second, and recovered, through a channel of limited bandwidth . " Signaling at the Nyquist rate " meant putting as many code pulses through a telegraph channel as its bandwidth would allow.
34.
:: : : Regarding sampling rate, see Hearing ( sense ) # Hearing in humans and Nyquist rate and you'll see why 44.1 kHz is considered sufficient for the human range of audio perception ( the reason 44.1 kHz was chosen exactly is a little more complicated, but not worth getting into here ).
35.
A more detailed understanding of how the rate of 1.544 Mbit / s was divided into channels is as follows . ( This explanation glosses over T1 voice communications, and deals mainly with the numbers involved . ) Given that the telephone system nominal voiceband ( including Hz, the required digital sampling rate is 8, 000 Hz ( see Nyquist rate ).
36.
An upper bound for the attainable modulation efficiency is given by the Nyquist rate or Hartley's law as follows : For a signaling alphabet with " M " alternative symbols, each symbol represents " N " = log 2 " M " bits . " N " is the modulation efficiency measured in " bit / symbol " or " bpcu ".
