Sound can be thought of like the ripples in a lake when you throw a stone into it creating ripples and the ripples travel outward in every direction. If you then took that lake and squeeze it into a canal those ripples would now be channeled to flow through the length of the canal. This is what’s happening when you connect your ductwork to a fan. All the sound waves from the fan are now being channeled through the ductwork.
The ductwork acts as a barrier preventing the sound waves from escaping, but there could be some breakout noise. Going back to our analogy, as the ripples travel through the canal still trying to protrude outward in every direction, some will fall on the shore or walls of the canal creating some noise. In the same way, breakout noise is the sound waves (caused by the airflow and/or fan) trying to escape through the duct.
This is where a fan silencer comes in. Placing a fan silencer in the airstream will help to absorb some of these sound waves. The amount of sound waves the silencer absorbs varies on acoustic media used in the silencer, the open area of the silencer (ratio of open space verses absorptive material), length of the silencer and materials used.
When the sound waves enter the silencer, the perforations in the baffle allow the sound wave to expand into the acoustic media of the baffle. The acoustic media is made up of millions of air pockets. When the sound waves impinge on the air pockets it causes the molecules to move and collide with each other dissipating energy in the form of heat. This is what gives you your noise reduction.
The more baffles you can put in a silencer the more noise reduction you can achieve, however you also increase the pressure drop. All fans create pressure to push air forward. If there is an obstruction creating resistance in the air stream, it produces pressure against the fan dropping the pressure the fan can create to push the air. There is a fine balance between the pressure drop allowed by the fan and the resistance of airflow created by the silencer.
At dB Noise Reduction our engineers have a wealth of knowledge and years of real world experience. We take the guess work out of the equation ensuring our customers get the highest performance from their industrial silencers. The quality of our products and the attention to customer service makes dB Noise Reduction the best in the business. Our business is to reduce noise caused by industry and create a peaceful environment.