Frequency Range of Audio

Discussion in 'Beginners, General Questions' started by JeremyErwin, May 16, 2006.

  1. JeremyErwin

    JeremyErwin Producer

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    Frequently, I see "Digital Audio" being advertised as 20 Hz --- 20 kHz, roughly matching the frequencies audible to a young pair of ears. The sampling frequency imposes a upper limit of 22 kHz. Add in some gradual filters, and there's your 20 kHz. But where does the lower limit 20 Hz come from? I know that most speakers, save some moderately expensive subwoofers aren't capable of reaching this deep, but svs does have a 16 Hz tune available. And apparently some find it useful.

    So, what's the story here? If one had a subwoofer capable of playing a 1 Hz tone, could one record that to CD and play it on this thing? And could one feel it, given sufficient decibels?
     
  2. Bob McElfresh

    Bob McElfresh Producer

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    Try finding a program called NCHTONE on the internet. It will let you pick a frequency, type of wave (sine, square, sawtooth) and duration. Then it will save the tone to a .WAV file that can be burned into a CD to create your own test-tone CD. I have done this when I tried mapping my room response.

    But - the lower the frequency, the closer the wireing appears as a direct-short. This is like shoving a fork into an AC outlet - lots of sparks, smoke and injury. (This is also why minutes of low-frequency sounds like in the Lobby Shootout scene in "The Matrix" throws some receivers into PROTECT mode.)

    I believe most subwoofers have a filter protecting the sub from too-low of a frequency.

    Could you perceive a 1 hz tone - yes I believe you could.
     
  3. John Garcia

    John Garcia Executive Producer

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    20Hz is a rough guideline, IMO. I can still hear a 20Hz tone, but at around 22Hz, it really just becomes more vibration than anything and at 16Hz it is really just air movement that you percieve - you don't hear it so much as feel it. It definitely adds to the realism of certain scenes.

    I wouldn't say most subs have a subsonic filter, because many inexpensive ones do not, but most decent subs and sub/plate amps do. However, I would say there are very few if any conventional subs that are actually capable of decent output below 10Hz. My sub is tuned to 17Hz and I use a 14Hz subsonic filter. There is something called a rotary woofer by Eminent Technology that has the ability to play down to 1Hz.

    Along the lines of what Bob said, you wouldn't need to record anything - you can download an MP3 of almost any frequency you want.
     

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