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Thread: HOG silencing

  1. #1

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    HOG silencing

    Hi all,

    I'm looking to get back into the hobby and am particularly excited about SM's HOG.

    I'm limited to SM's HOG because of cost, size, and time considerations (I'm poor, I can only set up a 29gal, and I don't have time to build my own ATS).

    Unfortunately, I'm sensitive to noise, and any kind of gurgling water noise will bother me. I mean any kind of gurgling noise. I don't mind the humming sound of pumps at all. Nor do I mind the periodic peristaltic pump topoff sound very much (not that I love it). I can also tolerate the giant chiller kicking on and turning the room into an airport hanger of noise once every couple hours. But constant gurgling even at the lowest level is something I know will bug me. Heck, I get annoyed when the humidifier in my room burps just a few times ever couple of hours.

    I read a post from SM elsewhere in which he stated that due to cost considerations, the HOG cannot accommodate the needs of someone who requires silent operation.

    That's fine, but I still want to see explore it.

    I was thinking some kind of silencer could be made. Tell me what you guys think about this. Keep in mind, I'm not skilled in these areas and my thoughts may sound silly to experts.

    Position the HOG under the water line for optimal water flow as described in the instructions. Bubbles then rise from the top of the unit, bursting at the water level and causing noise.

    Make some kind of shroud that extends from the top of the HOG where the bubbles exit to the water line and a few inches beyond. The shroud would provide a channel of sorts, through which the bubbles could rise and receive their silencing treatment. Something like a black pipe or rectangular acrylic assembly, maybe 6 to 8 inches long.

    The shroud is some kind of bubble bursting chamber - a housing in which bubbles can be made to burst in a way such that the bursting sound is silenced. Perhaps there is some principle of acoustics that can be used to cause the sound to be have an affect imposed on them that is opposite of echoing. I know in car audio applications, some kinds of principles of acoustics are used to build subwoofer boxes in a way that causes bass sound waves to be somehow multiplied into earth shaking booming. I believe it’s called an echo chamber. Perhaps the opposite of that acoustic principle can be used to reduce rather than magnify sound.

    Maybe the HOG silencing device would work similarly to however a silencer on a pistol works.

    And another thought - don't skimmers have to deal with this issue as well, and do so quite successfully? A skimmer is a column of unruly bubbles that rise and terminate in a way such that they're a frothing angry mob when the cup isn't in the skimmer. But when you drop the cup in, all becomes no more than a steady hum, or a steady something or other that's maybe like fairly well attenuated pink noise depending on the skimmer.

    In that regard, I guess one of the issues we're dealing with here is that the bubbles are large unlike a skimmer's micro-bubbles. So I guess large bubbles don't even out into a froth of steady noise, and tend to cause gurgling.

    And another thing, don't we need something to deal with those bubbles bursting at the surface to avoid what I believe is called salt spray? I mean that thing that happens in which salt gradually gets encrusted around the top of the tank in various areas like the canopy, tank frame, hoses and pipes and such.

    So, what do you guys think about this?

  2. #2
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    A thick cover helps a lot to reduce bubble noise. And yes you can run a tube to above the surface. Reduce bubble size too, but that will reduce filtering at some point.

    Just raise the cover to above the water line and you won't need a tube.

  3. #3

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    Ok it seems like it might work quietly enough raised above the water line as in this video you posted of the unboxing:

    http://www.youtube.com/watch?v=s8ed-RD8S6U

    But I need to ask about the lip on a 29gal glass tank. Is it possible to raise the unit above the water line in one of those tanks such that there are no bubbles without having to lower the water level in the tank below the black top frame? It seems like there might be a problem because the lips on those tanks might be an obstruction to raising the HOG upward enough to avoid bubbles.

    The reason I ask is that I don't like to have the water line visible below the black line of the top plastic frame. I don't like that look because it's what most tanks that aren't topped off look like. It's that dentist office fish tank look that I really like to avoid, and I do so with an autotopoff sustem.

  4. #4

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    *on second look at the video, I can see there's no way to raise up the HOG on glass tank to achieve no bubbles without lowering the water line. Am I right about that?

  5. #5

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    *the tube running up to the surface may solve all of these issues. Especially if perhaps the tube terminated in a foam thingy or something to even further dampen any escaping noise.

    Does the air bubble outlet on the top of the HOG have a single hole into which a tube could be inserted? In this video it seems like at some point the bubbles are all discharging from the top of the unit in one location.

    http://www.youtube.com/watch?v=s8ed-RD8S6U

    But in other moments before the unit seems to be settled out after placement, the bubbles are escaping in a line across the top that looks to be about one inch across. Is that just because the bubbles are escaping between the plastic housing of the HOG and the glass? If that's the case, do you think the unit could be modded by the user with a thin rubber strip or something to ensure the bubbles only escape at a single location into which a tube could be inserted? Thanks a lot for your guidance.

  6. #6
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    Correct, a protruding top frame would stop a regular non-custom-shaped cover from going higher.

    The HOG.5 and 1 have one small hole in the top where the bubbles exit when the covers are in place; when the covers are loose, bubbles will escape in many places.

  7. #7
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    An old post I know but I believe I have cracked the noise issue for many as I have posted recently. IMO this is the last hurdle the HOG's had to get over and improve on. I found my HOG2 with a powerful Tetratec AP300 air pump powering it to make an unacceptable amount of noise. Noise not from the pump I may had but from either the bubbles bursting below the waterline or the spitting out of water with the expelled air. See my post and cure for the problem here.
    http://algaescrubber.net/forums/show...-HOG2-Silenced

  8. #8

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    Now that's what I'm talkin about

  9. #9
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    Quote Originally Posted by Camineet View Post
    Now that's what I'm talkin about
    Works in a similar way to how a skimmer silencer works but inverted or it fills with water over a period and the spitting sound comes back however you could empty the bubble counter but there is no need if you invert it as I have shown. Try it and see for yourself.

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