Editing Voice frequency (section)

== Frequency band ==
In [[telephony]], the usable [[human voice|voice]] frequency band ranges from approximately 300 to 3400&nbsp;[[Hertz|Hz]].<ref name="bldrdoc">{{Cite web|url=https://www.its.bldrdoc.gov/fs-1037/dir-039/_5829.htm|archive-url=https://web.archive.org/web/20201020083412/https://www.its.bldrdoc.gov/fs-1037/dir-039/_5829.htm|archive-date=2020-10-20|title=Definition: Voice frequency}}</ref> It is for this reason that the [[ultra low frequency]] band of the [[electromagnetic spectrum]] between 300 and 3000&nbsp;Hz is also referred to as ''voice frequency'', being the electromagnetic energy that represents acoustic energy at [[baseband]]. The [[Bandwidth (signal processing)|bandwidth]] allocated for a single [[Voice channel|voice-frequency transmission channel]] is usually 4&nbsp;kHz, including [[guard band]]s,<ref name="bldrdoc"/> allowing a [[sampling rate]] of 8&nbsp;kHz to be used as the basis of the [[pulse-code modulation]] system used for the digital [[PSTN]]. Per the [[Nyquist–Shannon sampling theorem]], the sampling frequency (8&nbsp;kHz) must be at least twice the highest component of the voice frequency via appropriate filtering prior to sampling at discrete times (4&nbsp;kHz) for effective reconstruction of the voice signal.