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lowest hz produced

Discussion in 'Archived Threads 2001-2004' started by Joe.Kuta, Jun 6, 2002.

  1. Joe.Kuta

    Joe.Kuta Stunt Coordinator

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    Has a sub ever hit 1hz? under 1hz?
    heh I guess you could say no sound @ all is the lowest hz produced (0hz = 0 waves/sec = no sound). So, lowest hz w/ significant spl.
    just wonderin [​IMG]
     
  2. Chris Tsutsui

    Chris Tsutsui Screenwriter

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    Yeah the air outside has frequencies at 1hz at fractions of a micro decibel lasting for micro seconds that is inaudible to any known species.

    jk

    The lowest frequency that I use is 10hz on my 15" tempest. The sound it produces is basically the sound of my room rattling from vibrations.

    There would be absolutly no point in designing a HT speaker to hit 1hz because at any SPL is should still be inaudible. 1 hz @ 1 trillion decibels could perhaps vaporize a human being at 1 meter but I don't feel like thinking of what it would take for a speaker to do that.

    Instead I'll just start calculating the xmax for a 1" tweeter to produce 1 trillion decibels @ 1hz.
     
  3. Steve_Ma

    Steve_Ma Second Unit

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    Stuff below 20hz is interesting, but it kinda freaks-me-out alittle. At about 16-20hz (depending on the volume), I can hear wine glasses in the adjacent room rattling as well as some floorboard and wall vibrations, but no perceived bass "sound". Odd too, in the 10-16hz range, if I turn the volume up, I also feel alittle nauseous.

    Maybe I'm just a woos and can't handle the bass? I tend to leave my sub setting as neutral and flat as I can get it. I even steer clear of the "house curve." I like clean bass, but I suspect I prefer less of that really low stuff than many. I see some teens here and there driving around and I can sometimes "feel" the synth and techno bass coming from those small cars as they drive by. It amazes me! I wouldn't last 5 minutes in that environment. I'd blow lunch all over the dashboard. I suspect I might also have an anyerism...Or vaporize like Chris pointed out...Or something equally unpleasant.

    --Steve
     
  4. Brian Bunge

    Brian Bunge Producer

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  5. Steve_Ma

    Steve_Ma Second Unit

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    Well there you go....you learn something new every day. Thanks Brian. I thought I once read something about that from Richard Greene as well, but wasn't sure.

    And just to clarify, I didn't suspect that the car bass was necessarilly
     
  6. Brian Bunge

    Brian Bunge Producer

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    Steve,

    I remember sitting in a few cars where the bass levels caused real pressure on my eardrums and blurred vision. It was impressive, but after 30 seconds I was quite happy to get the hell outta there!

    Brian
     
  7. Joe.Kuta

    Joe.Kuta Stunt Coordinator

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    yea the rockford fosgate car blew out it's reinforced windows at a demonstration (not supposed to happen... or was it?!)
    I think it had like 152 or so db, maybe more.
    I'm SURE someone in the world has made uber-low hz though... maybe as a weapon as suggested? [​IMG]
     
  8. Rey_Ramos

    Rey_Ramos Agent

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  9. Terry Flink

    Terry Flink Stunt Coordinator

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  10. JerryW

    JerryW Supporting Actor

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    My EBS aligned (142L) Shiva puts out a respectable amount of pressure at 12Hz (due to room responses). It makes my dishes and glasses rattle in my cupboards (on the other side of the house), all kinds of rattles and creaks in the house, and does wierd things with my eardrums... very mild disorientation, head congestion like having a head cold.
    [​IMG] it's very cool. [​IMG]
    Though, I have some friends who don't like it and they claim it makes them feel nauseous... in fact another friend, while watching The Haunting, said she felt like a ghost was passing through her body (during the pipes scene). When a room pressurizes it can be a very disconcerting feeling for the "uninitiated".
     
  11. Dustin B

    Dustin B Producer

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    A single Tempest with 500W in a truck cab hit almost 153dB. The record as far as I know is some woman with a stupid number of 15" drivers and many kilowatts of power. She hit a little over 172dB.

    They say standing under a 747 engine is 140dB.

    That would mean that stereo would be percieved as 3 times as loud as the jet engine and I guess technically generating almost 2^10 (4096) times as much pressure as the 747 engine.
     
  12. Kevin_W

    Kevin_W Second Unit

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  13. Lee-c

    Lee-c Second Unit

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    Dustin:

    I believe that record you mentioned would be over 8 times as loud as the jet engine, not 3 times.

    By the way, volume at these sorts of levels is dangerous.

    If you are on the deck of an aircraft carrier during operations without earmuffs, you would be
    unconscious within minutes from the sound. You would be dead within about 40 minutes, IIRC.
     
  14. Chris Tsutsui

    Chris Tsutsui Screenwriter

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    if you want some serious spl, there are loud sonars and even underwater explosions that exceed 250 decibels (under water). This can cause fishes swim bladders to explode and cause instant deafness for sea lions and such. I heard about how our ocean is endanger and how this increased amount of ambient ocean noise is causing disruption for marine life (navigation, mating, etc.)
    We've seen examples of sound as a weapon in Mars attack [​IMG]
    I wonder how many decibels it would be if the moon collided with the earth at mach 3? hehe
    In my car I put my home theater's 214L dual vented tempest for a few weeks. I made a test CD with various tones, crossovers, and bass tests. It was a lot of fun to see cars stop 5 car lengths behind me at the intersection and get rude looks from people. I was only using a 200 watt bridged amp.
     
  15. Mark Seaton

    Mark Seaton Supporting Actor

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    Hi guys,

    This topic routinely pops up every so often. I will dig out some of the posts our designer and low frequency guru Tom Danley has made in other forums.

    What people don't realize is that any sealed subwoofer can produce DC output, ie a constant pressurization. The question becomes to what level. Our company has long been involved in reproduction of very low frequencies, and is where/why the ServoDrive mechanism was devised. The first project to work with such low frequencies was the Sonic Boom simulator which had one system in a concrete room with I believe 26 pairs of 15" ServoDriven cones to reproduce a sonic boom and test building materials and how they reacted to such SPL. In this confined space response was flat to the 2-3Hz range. The other part of the project was to project a sonic boom to the exterior of buildings, where Tom Danley designed various LARGE bass horns of rather wild operation which produced well in excess of 130dB down to the 5Hz range. Another rather interesting project was a 12Hz bass horn (~24' long IIRC) designed for avalanche control as an alternative to blasting.

    As for very low frequency production, I do have a subwoofer here that in a room about 16 x 24 produced flat response down to about 5Hz with some significant output in room. As it is a sealed design, by definition it can produce DC pressure. 5Hz is about the bottom limit of the processing algorithms used in the top surround processors so going much lower might be rather acedemic with current hardware.
     
  16. Dustin B

    Dustin B Producer

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    I'm very aware of how dangerous those levels are, I wouldn't go anywhere near those competitions.

    I was under the impression that a 3dB increase was a doubling of pressure while a 10dB increase was a perceived doubling of loudness. So a 30dB increase would seem 3 times as loud, whilt the pressure increase would be almost 5000 times (this second part doesn't seem right to me though).
     
  17. Joe.Kuta

    Joe.Kuta Stunt Coordinator

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    imagine if those spl contests were done w/ mid to high range frequencies... bloody eardrums.
     
  18. Mark Seaton

    Mark Seaton Supporting Actor

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    For the record, 3dB is twice the acoustic power. 10dB is a commonly referred to figure as what is percieved as aproximately twice the loudness. This figure does fall in line with our understanding of hearing, so is not entirely arbitrary.
     
  19. Dustin B

    Dustin B Producer

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    Could you give a definition of "acoustic power" Mark? What exactly is being doubled when there is a 3dB increase?
     
  20. Michael R Price

    Michael R Price Screenwriter

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    So Mark, how much equalization did you use to get to 5 Hz from a sealed box? Or is this some new Servodrive trick I haven't heard about yet?

    Also, another random question: Under the 'tuning' frequency of a horn, does the driver get unloaded like in a ported system? Or does it work like a sealex box rolloff below there, keeping driver movements in check?

    Does 130dB or other absurd levels in the infrasonic region damage hearing as much as such a level at more common frequencies would?

    Dustin, I see it like this. dB is defined as a 10 dB increase equaling a tenfold increase in amplitude. 2x the amplitude thus equals 6.0206 dB. However, the actual acoustic power in the air is proportional to the square of the amplitude. Hence, a doubling of acoustic power requires 1.414 times the amplitude, or 3.0103 dB.
     

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