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What does a frequency of 100 Hz mean?

What does a frequency of 100 Hz mean?
Alex from Medway (Aged 5-14)

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15 Responses

  1. Simply a wave that “oscillates” (move backwards and forwards, or up and down) 100 times per second.

  2. A frequency of 100 Hz means 100 revolutions or cycles per second

  3. Hz is just posh fancy science speak for “per second”. Picture yourself standing at the beach paddling in the sea. Waves are coming in past you and you count how many of them come past you in a minute, say. Suppose you count 6. 6 waves pass you in 60 seconds so you could say that on average, a tenth of a wave passes you in a second (this is 6 waves divided by 60 seconds). So the frequency of the waves is a tenth, or 0.1 per second. This is 0.1Hz.

    Now, you often see Hz on radios and the like. The signal is sent using a different sort of wave. However, you can still measure how many waves pass per second. On a piece of equipment, the number may refer to the frequency of the waves that it is able to detect.

    Hope that helps.

  4. Hertz (Hz) means per second, so something that happens at 100 Hz happens 100 times a second.

    For example the second hand on a clock ticks at 1Hz.

    It’s interesting that you ask specifically about 100Hz, I would guess that you saw it on an appliance, possibly a television? So what is happening at 100 Hz in a television? That’s the rate at which the picture changes. Televisions aren’t actually showing moving objects they are showing different still pictures (just like photographs) but changing them 100 times a second, this makes it look like objects are moving across the screen.

    100 times a second is common in LCD TVs these days, but in the past the picture changed less frequently than that. If you have an old television or know someone who does, look at the television at first it doesn’t seem to be flickering at all. Now look at it again with the television just on the edge of what you can see (in other words, look at it out of the corner of your eye), you should now be able to see it flickering as the corner of your eye is more sensitive.

    If you don’t have access to an older Tv or if that doesn’t work, there is another way you might see this. Next time you see a computer in the background on TV (for example on the news), you should be able to see that the screens look a bit strange, almost as if they are flashing! This is because you have the combined flashing of images on your TV and on the monitor in the background where they are filming, this has the effect of reducing the frequency of the flashing to a rate that your eye might be able to see.

  5. It just means that that thing happens 100 times per second. The maximum speed that people can see things flicker (say, on a TV screen) is about 60Hz. Faster than that everything just merges into a constant stream, like on TV or film.

  6. Hi Alex.

    Lets examine the question a little bit first.

    Q: What does a frequency of 100Hz mean?

    There’s quite a lot in your question!

    First of all, the word “frequency”, comes from the word “frequent”, meaning “how often does something happen”?,
    So you could say something like:
    Cars go past my house quite frequently, about 10 every minute, or you could say, if I tie a weight on the end of a string, hold it up and let it swing, it swings backwards and forwards so many times a second, or so many times a minute. ….. so

    We have thie idea now of something that happens so many times per minute, or per second or what ever.

    If we look at say a guitar string, and “pluck it”, it makes a sound, and if you look carefully at the string, you’ll see that it “vibrates” backwards and forwards quite quickly, and in fact for many “notes” on the guitar, the strings vibrate at well over 100 times a second, and so you can say in general terms that:
    a particular string vibrates at a frequency of so many times per second.

    If we picked a string on the guitar that vibrated exactly 100 times per second, we would hear a musical note that repesents a sound wave that also is “vibrating” 100 times a second. ***

    and, in times gone by, in this case you would have quite correctly said that the string would have a frequency of 100 “cycles per second”, where the idea of a “cycle” was the “complete” movement of the string, or swing of your weight on the end of the string from one point, and back again to the same point,
    so a pendulumn for example would be said to complete one cycle as it swings from say left to rignt, and back again to its most “left hand” position

    Now,,

    The only “bit” left is the Hz bit, which is shorthand for Hertz, who was a famous scientist, whose name is now shortened to Hz, and is used instead of “cycles per second” for posterity.

    so 100Hz is something that happens, or vibrates 100 times per second

    *** For the musicians here, the note “A” immediately above middle C on a piano vibrates at 440Hz (concert pitch) , middle C 261.25 Hz, the A below Middle C 220 Hz. next the A below that 110 Hz, and the G below that A at about 98 Hz, so …… a musical or “sound” frequency of 100 Hz is just slightly sharp of 2 “G’s” below middle C

  7. some speakers have 46Hz-25kHz but im wondering if i get greater than 46Hz-25kHz or less does it means that i will get better audio quality?

  8. Anthony-
    the numbers you are speaking of (46Hz-25kHz) is the frequency range of a speaker. For instance a 10Hz sound frequency is a very low bass tone where 12-15 kHz is where most human speech resides. This is a little different than electrical frequency as they discussed earlier in the post. Most decent speaker operate at frequency from 20Hz to 20kHz, with the higher end speakers dipping down as low as 12Hz to get that earth-shattering bass.
    I hope this helps.

  9. Ooops – in the last post i meant to say that the high-end is in the 25-30 kHz range – not 20kHz as I stated. Sorry for the error.

  10. My friend on Facebook shared this link and I’m not dissapointed that I came here.

  11. Ron Baker-

    I just happened to stumble across this web page. I am a professional audio engineer so thought I might correct your post a little and help you learn more about sound!

    Humans cannot hear any lower than 20Hz and any higher than 20KHz… although this is normally more like 16KHz in adults because of hearing damage.

    Humans do not speak at 12 – 15KHz! Listen to how high pitched that is on a tone generator and you will see what I mean! Humans have an increased sensitivity of hearing somewhere between 3KHz and 5KHz because the canal in the ear acts as a closed tube resonator (google it!).

    When looking for a decent set of speakers frequency response is as, if not more, important as the frequency range.

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  13. Talking about 100hz. I have Sony TV advertised at 100HZ. On the information bar which appears on turning on the TV it shows 25 Hz and 50 hz on the national station. Am I being under Hzed and if so what can be done about it. I might add I have a clear picture.

  14. Why there is only LED tv with 1oo Hz and not 200 or more as in LCD or Plasma Tv.?

  15. I found this link when doing a search on google, glad I stumbled across this webpage. If an piece of technology states it is operating on the frequency of 100hz or a measuring frequency as I understand this would mean that it is saying it does a measurement 100 times per second. Great information

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