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Frequency of Thunder?

Discussion in 'Sound, Music, and Intercom' started by dvsDave, Aug 27, 2003.

  1. dvsDave

    dvsDave Benevolent Dictator Administrator Senior Team CB Mods

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    I am looking to create some serious surround thunder effects for our stage.

    I was wondering if anyone knew the frequency range of deep, rumbling thunder and the range a really sharp crack of thunder.

    Anybody have any experience with this?
  2. wolf825

    wolf825 Senior Team Emeritus Premium Member

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    Yup. Well...off stage "Thunder" sound effects for a stage production can be made with a hanging piece of hammered sheet metal--approx 5-6' tall and about 4 feet wide, freehanging with a wood slat at the top and bottom with a handle. Any smaller a sheet and it would not be as "full" sounding. This is then smacked with a padded beater or twisted and shaken. Usually you do two mic's--one top and one mid-low area, a condensor (AT4041 or SM81) and a wide diaphram dynamic (MD 421 or EV RE20) work well, and you mix the two to taste with a bit of EQ and add some effects to round it all out in pitch or delay, and resonance.

    If you're just looking for sound frequency's--the chest rumbling resonance is in the 70-80hz range. The lower grumblings that add so much "air" to the low end are in the 40-50 hz range, and the sharp crack of thunder is usually in the 2k area with a mid range lower harmonic in the 600-800hz range to add a thickness to the crack. Remember--a crack of thunder is not sibilant--but a streak of lighting CAN be heavy on the hiss and higher freq's if you want to add that in. These freq's can either be boosted or cut depending on how things sound, to help enhance the sound on a channel strip for a mic, or you can toss in a pitch shifter or flanger on the negative grade, or positive grade, which will add some distortion and enhance it that way and change it. Now IF you are doing a "surround" sound--you will want to do individual mic's (as many as each area of surround) on individual tracks that you can pan in different orientations to have that psychoacoustic effect to the tracks go all around a room, or you can double your tracks and change your pans and fix that in mix down. You may want to do a compressor, but I would opt for a slow closing gate, or even a frequency consiouse gate, to give you that "dead" silence in between, and open when you want it to open so your thunder effect is not audibly predictable--but it leaps out and is suddenly there. Not too difficult...and kinda fun task to play with...sounds like a fun time.

    -wolf
  3. TechDirector

    TechDirector Member

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    wolf, how did you find all this information? Did you go to a lightning (or thunder) research center? lol.
  4. Jo-JotheSoundDog

    Jo-JotheSoundDog Member

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    The biggest problem I have had with thunder is not many theatres can afford speakers that can properly recreate all the needed frequencies of what everyone knows as the sound of thunder. I remeber years ago I saw a show on Broadway, huge budget show. It got to the scene where they needed thunder. First off it was a horrible recording. Second off they tried to pump way to much bass out the speakers.
    My question is why are you trying to go with surround thunder?
    Reasons why I see this as a bad idea.
    1. Thunder in its nature has some seriously low bass even going well into the subharmonics. One or two well placed good subs could "shake" the house. But when you start dealing with the smaller mid-high cabinets that most theatres have for surround speakers their frequency range isn't low enough to acurately reproduce the sound.
    2. When I hear the term surround, I think of true surround. Where you have all sorts of stereo imaging. And thunder has has a little change to it, but not enough to warrant going for the surround imaging.

    If you have the ability to get a couple of subs under the seats, it really helps "shake that thang".

    If you find a decent thender sound effect. One way to make it a little more yours, is to take it throw it through a pitch shifter and get some good low rumbling. You don't have to pay too much attention to the quality, just make sure its a nice low rumble. Then take that and layer it over the original sound.

    When you speak of frequencies there are quite a few freqs invloved and a nice spectrum from 70 on down to 20.

    Hope this helps some.
  5. dvsDave

    dvsDave Benevolent Dictator Administrator Senior Team CB Mods

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    oh yeaahhh

    "Will six eighteen inch subs do the job?" asks the tech

    8O my reaction exactly

    followed by

    8) ohhh yeaah

    I have a couple of really good sharp thunder cracks from a surround sound fx library. no issue there... but I think running the deep effects is going to take a careful setup thru a pitch shifter and carefully set crossovers... speaking of crossovers, with 6 subs, should I set them at different frequencies or have all of them driving the same sound?
  6. wolf825

    wolf825 Senior Team Emeritus Premium Member

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    hehe..nope no NOAA info from me<g>..just been around a bit and been asked to do a lot of bizarre sounds and mixes..

    wolf
  7. wolf825

    wolf825 Senior Team Emeritus Premium Member

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    Re: oh yeaahhh



    For the new techs who may not know about Crossovers: Crossovers take an audio signal and split the freuqency's between the cabinets to better have the cabinets/drivers/speakers run the frequency ranges they were designed for, best and most effeciently..and the new Digital processors and Xovers allow you to boost or cut certain frequencys to compensate for manufactuerers processors that may not be with the cabinets. It also allows you to do precision time alignment for the drivers and cabinets to keep things in phase and time delays if you space things out. Since sound is something that moves in air at a specific speed, offsetting drivers can cause "phase" and time alighment problems that can effect the sound. Typically--you cannot hear most time alignment differences up to about 8-10 milliseconds, so some analyzers (like SMAART, TEF, SIMM etc) are used to nail the delays precisely or close to it while analyzing a system signal & room response. How you would set these depends a bit on the speaker cabinets, amps and frequency range. You can do some cool time alignment and "phase" tricks with these. Phase is something that if done correctly will make signals additive, or completely cancel out, or give a psychoacoustic effect depending on the delay lengths. Ok..enough class lecture to whet the appitite for now =)

    Overall to answer your question--if your subs have a very low range (not all 18" subs are created equal--are they reflex, ported or hornloaded?) your placement will vary how you delay them. If you have them side by side or separate--overall then your xover frequency should match for the most part--again tho this is pending the response of the cabinets and the rest of your system. IOW if your subs are x-over to about 120hz, but your mids don't pick up below say 250 hz--there is a noticable gap between 120hz and 250hz you will want to try to fill or compensate for or the sound can be empty in that range. Changing the x-over frequency's between cabinets is not going to accomplish much except limit the range the cabinet--one, two or all, will reproduce. Won't do much to help your idea or effect if the rest of your system cannot compensate for the "gap" you leave between subs and mids IMO. Unless you had something waay cool like a few Servo-Drive cabinets that do the subsonic frequency's, and some other 18" subs, I would keep all your xover frequency's the same.

    hope this helps...
    -wolf
    PS--almost done with the first "what is sound" tutorial...u should see it by labor day. proof read it and see if its too vague or too technical..and I'll adjust it. -w
  8. Jo-JotheSoundDog

    Jo-JotheSoundDog Member

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    Ahh, but it's not the size, it's how you use it.



    So lemme get this straight, You are planning on playing the thunder right off the CD ( because of the surround coding) Through a pitch shifter live every performance? I have yet to touch surround sound fx, mainly because I find it easier to create my own multidimensional soundscapes. So I am curious if there is any way to edit the sounds without destroying the codes. If that is the case, I can tell you that I am not a fan. One of my favorite parts to my job is building show specific effects. The least favorite is sitting through libraries of sound effects looking for something that will work. But that is just me.

    As for the X-over question. Without knowing the space it is a hard question to answer it might do something, but I doubt it. The real reason is if you were playing a multi-track and had the ability to control what you were sending to the speaker, you could do something like record a stereo thunder cue to two tracks totally roll off the high end, throw it through a pitchshifter knocking it down a couple steps crank up the lows and record it to the Multi-track. Than take the same thunder cue roll off the low end boost the freq of the crack and record. Than take these two effects and layer one over the second and record.
    For playback take the two tracks with no highs and play through the under house subs. Send the high crack to a pair of mid high cabinets. And lastly send the total image to a pair of in house subs. Then play with the levels for 15 to 20 minutes until crust is golden brown.

    And now for the X-over question.
    First off are all the subs identical? If they are there is not a whole lot of variation you can do. You can roll off the high end lower. But I don't see it really helping if you have 6 speakers playing the same source of sound.
    Second is this the only sound effect in the show that has the potential to use these speakers? By changing the X-over config you run the possibility of screwing up how other sounds will sound.

    But than again that is just my first opinion. The space could actually be more sound friendly than I am used to, and it might just work and sound
    amazing. I would say if you have the time try it. The worse that could happen is you could have fun with a new experiment.
  9. dvsDave

    dvsDave Benevolent Dictator Administrator Senior Team CB Mods

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    for right now.. this is just an experiment, but it may be in a show in march or april.
  10. ship

    ship Senior Team Emeritus Premium Member

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    You guys make it seem so simple that I understood most of what you were talking about. Now it's just a question of all those knobs and buttons... LOL in my first use of it.

    "If you have the ability to get a couple of subs under the seats, it really helps "shake that thang".

    That I do have some knowledge of. Back in my old theater, I was pissed when the new sound guy pissed away the budget on some "sub-wolfers" as it were for me just speakers to sit under the audience, but the first time I felt them, Oh' Yea! Highly recommended for all places. Oh' yea!

    Still if a proper procenium theater, it still would be cool to play test and use Wolf's first idea especially if it could be miked or timed to some sub-wofers on a delay and the rest of the surround as it were. But Oh' yea to the vibrations - thanks for the memories that I had forgotten about.

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