Tutorial: How-to

4 Ways to Quiet a Noisy Machine

Apply acoustical foam or fiberglass blankets to ceilings and walls of room.

• Maximum noise reduction: 6-9 decibels (30-40% decrease in loudness).
• Advantages: No inconvenience to workers.
• Disadvantages: 75% of the room must be treated regardless of the size of the noise source.
• What materials? Hanging acoustical baffles from the ceiling, walls to be covered by acoustical foam or quilted fiberglass blankets.

Apply acoustical foam or fiberglass blankets behind the noise source.

• Maximum noise reduction: 1-2 decibels if noise sprays noise our into room, 4-6 decibels if noise is sprayed directly onto wall (such as noisy vent on the back of the machine).
• Advantages: No inconvenience to workers
• How much foam? Treat the wall behind the machine with about twice the square footage of the "shadows" of the machine on the wall.

Build an acoustical curtain system around the noise source.

• Maximum noise reduction: 6-15 decibels.
• Advantages: Very good noise reduction.
• Concerns: May have to incorporate view window for visibility and/or sliding panels for access.
• What size? At a minimum, 8' high. Typically they should be double the height of the noise source.

Build a complete enclosure.

• Noise reduction: Up to 20-30 decibels.
• Advantages: Maximum noise reduction.
• Concerns: May have to incorporate view windows for visibility and/or doors for access as well as ventilation baffle(s) for air flow.

A note on decibels:

• A 5 decibel noise reduction represents a reduction of 50% of the acoustical energy produced by the noise source.
• OSHA also states that a 5 db noise reduction represents a 50% decrease in the risk of hearing loss. (Noises reduced by 5 decibels sound about 30% quieter.)
• A 10 decibel reduction represents a 90% decrease in acoustical energy and sounds half as loud.

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