Between extractor fans, circulating fans, air stone pumps and reservoir pumps, maintaining a climate-controlled indoor garden can make a lot of noise. The constant humming, buzzing and vibrating can leak into the ears of your neighbors below, above or on either side, and you can’t blame it on the refrigerator when they complain. With a little budget and a big toke of stoner ingenuity you can follow these tips to make your growroom almost completely silent.
Use a duct fan that has the exact rating you need for the grow space
The more air a fan draws the louder it will be, and the more work you’ll have to do to silence it. The first step in building a silent growroom is buying a fan that draws the exact amount of air you need, instead of trying to reduce the speed of a fan that is too powerful. Reducing the fan speed with controllers forces the fan to run at suboptimal conditions and will lower its life and performance. The air in your growroom should exchange every five to eight minutes, so to figure out how many cubit feet of air per minute (CFM) your fan should move, use this online CFM calculator. If you are pushing the air through a charcoal filter before exiting, you’ll need a slightly more powerful fan to compensate for this loss in pressure, so check the rating on any filters you may use and it to your CFM calculation.
Use a muffler for the air exiting the growroom
Exhaust air exiting a duct at high speeds makes a very audible “wooshing” sound that has given away countless grow-ops. You can either purchase or build a muffler for very little money. The muffler drops the speed of the air and reduces turbulence, and even a DIY setup made with a trash bin, glass wool and chicken wire can make your airflow completely inaudible.
Use fabric and/or insulated ducting
Both flexi-metallic and rigid-metallic ducting can carry vibrations and cause noisy turbulence that compromise your stealth. Not only is fabric ducting easier to install than either of the other, more common options, it renders excellently to ventilation situations that require silence. Many stealthy growers also recommend insulated ducting for the last stretch of the duct before the air exits to the outside. While it may cost a pretty penny, the fiberglass insulation designed to insulate heat also absorbs sound excellently. If you do use ducting that isn’t fabric, make sure to minimize the amount of bends and turns, which create noisy turbulence.
Suspend your vent fan with bungee cords in an enclosed box
In order to prevent vibrations the fan creates from going through the ground, walls or ceilings, it shouldn’t directly touch any of these surfaces. Enclosing the fan in a wooden box and suspending it from the ceiling with bungee cords does not allow any vibrations to travel beyond the enclosure; check out this great instructional with photos. Seal the cracks up with acoustically rated caulk and you’re good to go. If you have metal air ducts, suspending them with bungee words from the ceiling will drastically reduce sound transmission through the ceiling.
Isolate airstone and water pumps from the floor
Air and water pumps typically sit on the ground and produce noise and vibrations that are capable of penetrating walls and floors. Placing a high-density foam or rubber surface between them and the ground will attenuate the vibrations making them as quiet as possible. If you already invested in acoustical duct wrap, or some other sound-proofing material, cut out a few squares and place the pumps on them. Just make sure that whatever it is, it’s made of a flame retardant material.
Increase in-line resistance of air pump with extra airstones
Putting the noisy air pumps on foam padding blocks vibrations from going through the floor, but they will still emit sound into the surrounding air, and a lot of it. It may sound counterintuitive, but air pumps make more noise the less resistance they work against. Placing more airstones in series will make your pump work much quieter, in addition to providing more distributed oxygenation to your reservoir; it just takes some simple plumbing.
Sound proof the walls and floor of the entire room
If the above solutions aren’t enough because you really need silence, the entire room needs soundproofing. Certain architectural techniques and materials can be incorporated into the building of a house or in the walls of a particular room, but tearing up walls and flooring isn’t an option for people that pay rent. Installing rubber floor underlayments, that go beneath the linoleum or wood floor surface don’t entail as much work or expertise as ripping up walls, and may be the first option for someone who wants to make a permanent alteration to the room. Without making permanent alterations, a grower can hang up vinyl curtains (like they use in loading bays and garages) for relatively cheap. Pyramid panel acoustical foam hung on the walls will cut down on high pitch frequencies, but blocking low and medium tones requires heavy materials like rubber. Don’t waste your time with egg cartons, they are highly flammable and don’t block as much sound as you think. Seal up all the cracks with acoustically rated caulk and make sure that everything is completely fire-safe and all the materials are non-flammable!
Photo credit: Felix Green