Talk:Frequency

440 Hz

Is it not true that the A tuning note is only 440 Hz in the United States, while in fact 442 Hz in Europe? Perhaps this should be changed.

See Pitch (music) — Omegatron 14:36, 20 February 2006 (UTC)

Changing wavelength

I was just wondering about the comment that when a wave goes from one medium to another, the frequency remains more or less the same, only the wavelength changes -- this doesn't make sense to me. If frequency has an inverse relationship to wavelength, how can one change without the other?

It's correct. Suppose the wave propagates 340 metre per second in the first medium, and 680 m/s in the second, and suppose the frequency is 340 hertz so that the period (i.e. the time it takes for one complete oscillation) is 1/340 seconds. These values fit a sound (a rather deep tone) passing from air into a somewhat harder medium. Then, in air, this sound travels 1 metre per period, so the wavelength is 1 metre. In the harder medium, it will travel 2 metre in the same time, doubling the wavelength.

Put differently: Yes, frequency has an inverse relationship to wavelength in a given medium, but the constant of proportionality depends on the medium.--Niels Ø 09:35, Apr 15, 2005 (UTC)

Invariance of frequency

Just wondering if any one has thought about why frequency is invariant (apart from doppler effect). ie whatever you do to a signal, you can change its wavelength and or velocity but you cant change its frequency. (I'm not considering mixers here). Any musings from anyone as to why this should be so?? --Light current 06:52, 23 November 2005 (UTC)

Because it's based on time? Theory of relativity and all that?

I'm not sure if it's worth pointing out, but the frequency of a pre-recorded signal can certainly be changed by playing it back at a different speed. Practically, if you sample something with an incorrect sampling frequency (you think it's 48 kHz but the oscillator's actually running at 48.01 kHz), then reproduce it correctly, the frequencies will be shifted.

Plus there are things like pitch shifters to simulate a change in frequency, though that's even less relevant. — Omegatron 21:32, 7 December 2005 (UTC)

Quite correct about pre recorded signals, but Im thinking more of a 'pitch shifting' method but broad band and not using mixers (multipliers). I guess it just can't be done? --Light current 22:07, 12 December 2005 (UTC)

It could probably be done with wormholes. :-) — Omegatron 15:02, 18 February 2006 (UTC)

Wave-theory / frequence?

Wave-theory?

When wave (which is matter vibration) goes through matter (like, air, water, space-atmospehre, etc.) it changes.

At starting point wave start to goes and frequence is 1Hz. Speed 1m/s. Then wave length is 1m.

When wave travell through matter, alla other matter-conditions influence that wave and therefore, speed, wave length, and also then frequence, change.

I have thought this issue about 9 years and i'm sure that 1wave cannot be just same kind when it's flow through matter.

I draw a scientist picture of this issue.

You can read it page,

http://www.moheitulkuri.fi/w/wave

e-mail; aaltoteoria@moheitulkuri.fi

Nature example. Thunder-voice is very high (amplitude, and frequence(ex.5000Hz) near the thunderbolt. But, same voice(wave) is much lower freq-voice longer distance(ex.100Hz).

Also. If you drop rock to water. Water-wave start to travell. Near drop-point (1m) wave is example, 10cm length and f=10Hz, speed 1m/s. But when you follow this one wave then longer distance ex.100m to dropping point, wave lengt is more than 10cm, also speed is lower than 1m/s. Therefore frequence is also lower than 10Hz.

I have made wave-length calculator example of this issue, on my web-page. You can get and study of this calculator on address;

english http://www.moheitulkuri.fi/w/wavecalculator.xls

What is the travell-distance when can see that wave is transform?

I thougt that it depends of, starting frequence, matter-conditions, and amplitude, but also so called square-law.

But example. frequence is 10 000 000 Hz and travell through space it stay allmost same kind maybe. example 1 000 000 000 km.

I dont know what is frequence-transition on radiowave at much longer distance?

br. Heikki. 5.2.2006 Heikki 10:19, 20 February 2006 (UTC)