Hertz

:''See also the car rental company, The Hertz Corporation'' The hertz (symbol Hz) is the SI unit of frequency. It is named in honour of the Germany physicist Heinrich Rudolf Hertz who made some important contributions to science in the field of electromagnetism. One hertz simply means "one per second" (1 / s); 100 Hz means "one hundred per second", and so on. The unit may be applied to any periodic event – for example, a clock might be said to tick at 1 Hz, or a human heart might be said to beat at 1.2 Hz. The name hertz was adopted by the CGPM (''Conf�rence g�n�rale des poids et mesures'') in 1960, replacing the previous name for the unit, ''cycles per second'' (cps), along with its related multiples (''kilocycles'', ''megacycles'', and so forth). Hertz replaced cycles in common use by 1970. == SI Multiples ==

1 kilohertz	kHz	10³ Hz	1 000 Hz
1 megahertz	MHz	10⁶ Hz	1 000 000 Hz
1 gigahertz	GHz	10⁹ Hz	1 000 000 000 Hz
1 terahertz	THz	10¹² Hz	1 000 000 000 000 Hz
1 petahertz	PHz	10¹⁵ Hz	1 000 000 000 000 000 Hz
1 exahertz	EHz	10¹⁸ Hz	1 000 000 000 000 000 000 Hz

== Examples == *10 Hz, cyclic rate of a typical automobile engine at idle (equivalent to 600 rpm) *50 Hz or 60 Hz (50 Hz for European AC, Tokyo AC or 60 Hz for American AC, Osaka AC), electromagnetic — standard alternating current Mains electric power *20 Hz to ~16 kHz, acoustics — normal range of adult human hearing (most children and some animals perceive sounds outside this range) *100 Hz, cyclic rate of a typical automobile engine at redline (equivalent to 6000 rpm) *261.626 Hz, acoustic — the musical note middle C *440 Hz, acoustic — Pitch (music) (A above middle C), used for tuning musical instruments *740 kHz, transitions — the clock speed of the world's first commercial microprocessor, the Intel 4004 (1971) *1 MHz to 8 MHz, transitions — clock speeds of early home computer/personal computers (mid-1970s to mid-1980s) *30 MHz to 300 MHz, electromagnetic — VHF terrestrial television television broadcasts *88 MHz to 108 MHz, electromagnetic — FM radio broadcasts *1420 MHz, the frequency of the hyperfine transition of hydrogen, the most common element in the universe. *3.73 GHz, transitions — clock speed of the Pentium 4#Prescott microprocessor (as of 2005) *428 THz to 750 THz, electromagnetic — optical spectrum light, from red to violet (color) *30 PHz, electromagnetic — x-rays Lower frequencies: *Once per minute: about 16.67 mHz *Hourly: about 277.8 �Hz *Daily: about 11.57 �Hz *Weekly: about 1.653 �Hz *Monthly (on average): about 380.5 nHz *Yearly: about 31.71 nHz **Once per decade: about 3.171 nHz, once per century: about 317.1 pHz, once per millennium: about 31.71 pHz SI derived units Units of frequency

Hertz

Can the pages Megahertz, Kilohertz etc be more than stubs? Should we redirect them here, where we can put a list of SI multiples? -- User:Tarquin :No. I think we should also have picohertz, yottahertz etc. Just kidding. It might be useful think about consolidating all these SI pages so that the article is at the preferred SI standard with all the other prefixed stuff redirecting to it. Hm. That would mean that gram would redirect to kilogram, kilometre to metre, square kilometre to square metre etc. --User:Maveric149 ::One picohertz is approximately equivalent to once per 31710 years. User:JIP — JIP | User talk:JIP 15:11, 1 May 2005 (UTC) :Megahertz should be left as-is, whereas the rest (e.g. Kilohertz) should simply be merged into Hertz. == Audio frequency ranges == I noticed that frequency ranges were listed for visible light, but only a few select audio frequencies were listed. Might it be useful to note that the range from roughly 20Hz to roughly 16KHz covers the ability of the human ear to distinguish sounds? Or even note the higher ranges (or lower) used by other animals (dogs, whales, etc)? -- T.Moore :Good suggestion; thanks! I'll see to it. --User:Wernher 22:35, 2 Jul 2004 (UTC) == Hz and human range of hearing == Can someone help me understand why dog whistles are considered 'silent' (as in beyond the range of human hearing) when most of them are (at about 5800 Hz) well within the range of audible sound (20Hz - 16kHz) for human hearing? Thx. ::Because the maximum human ear performances are in the middle frequencies. A sound as treble as 6kHz has to be quite loud for you to clearly hear it. ==Capitals and lower case== Anybody know why in "kHz", the "k" is lower case, whereas in "MHz" the "M" is upper? User:DanielVonEhren 21:46, 25 Jan 2005 (UTC) :The SI system of numbers has k (or kilo) as the prefix for 1000, m (or micro)as the prefix for a millionth and M (or Mega) as the prefix for a 1,000,000. So that MHz is 1,000,000 Hz and mHz is 1/1,000,000Hz. See Kilo. User:Tiles 06:31, 27 Jan 2005 (UTC) Excellent! The Kilo page has all sorts of things I'd looked at all my life, but never really saw. Thanks Wellington (great place, by the way). User:DanielVonEhren 05:35, 28 Jan 2005 (UTC)

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