Handbook of Noise Control Materials

Product catalog summary

Section I: Basic Concepts of Blocking and Absorbing Sound
Acoustic insulation materials function through absorption and reflection. Absorption dissipates sound as heat, while reflection redirects noise. A composite insulation material can serve both purposes. For example, enclosing an engine with plywood can reduce noise, but adding absorptive materials like fiberglass or foam further decreases reverberation and noise levels.

Section I.B: Variables Affecting Performance
Key variables include the weight of the barrier layer and the thickness of absorption and decoupling layers. Effective noise reduction requires careful consideration of these factors, especially for mid and bass frequencies. Thicker absorptive layers are more effective for bass frequencies.

Section II: Vibration Damping Treatment
Damping materials reduce structure-borne noise by absorbing vibrational energy. Methods include extensional and constrained layer treatments. Proper bonding of damping materials to panels is crucial for effectiveness. Panel size and material type influence the choice of damping method.

Section III: Materials
A. Absorption: Common materials include open-cell urethane foams and fiberglass, both effective for sound absorption. Urethane is flexible and easier to handle, while fiberglass is fire-resistant.
B. Mass Layers: Effective mass layers are non-porous and limp, with vinyl being a common choice due to its density and flexibility.
C. Damping: Damping materials come in various forms and require appropriate adhesives for effective application.

Section IV: Practical Considerations
Absorptive materials can be strategically omitted without significant noise increase. Barriers must be sealed to prevent noise leakage. Effective damping depends on the surface's resonance and proper bonding of materials.

Section V: Noise Treatment Inside Cabin
Inside the cabin, absorptive materials like perforated vinyl over foam can reduce noise. Underlayment with a plastic mass layer over foam beneath carpets can further decrease noise transmission from the engine room.

Catalog excerpts

ection I. A. Basic Concepts of Blocking and Absorbing Sound B. Variables Affecting Performance Section II. Vibration Damping Treatment Section IV. Practical Considerations Section V. Noise Treatment Inside Cabin

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A. BASIC CONCEPTS OF BLOCKING AND ABSORBING SOUND Acoustic insulation materials work by two processes: absorption of sound energy, which dissipates sound as heat ener- gy and reflection, which reflects noise away from a location where quieting is desired. A single composite insulation mate- rial will be effective as both an absorber and a reflector. Considering the example of an engine in a boat, if it is sitting open with no enclosure around it, it will create a very loud noise throughout the boat, perhaps as much as 105 dBA . If we install an engine box around the motor using 5/8" thick plywood,...

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The most significant variables for noise control materials are weight of the reflecting barrier layer and thickness of the absorption and decoupling lay- ers. Secondary factors are the protective surface fac- ing materials and materials for the mass layer. The particular type of acoustic foam or fiberglass is of lesser importance among the legitimate and effective acoustic materials available. The universal problem in attenuating noise of marine engines, generators, and propellers is reduc- tion of mid and bass frequency rumbles. High fre- quency sounds of turbo chargers, gearboxes, engine valve...

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BASIC DISCUSSION OF VIBRATION DAMPING TREATMENTS Damping materials absorb vibrational energy from resonating panels in a direct analogy to sound absorbing materials interacting with noise in the air. By absorbing energy, damping reduces the structure- borne noise radiated from the panel to which it is applied. Damping also reduces the structureborne noise traversing the treated panel and traveling to more remote parts of the boat (structure). Methods of vibration damping include "extensional" and "constrained layer" treatments. Extensional damping materials are applied as a single layer direct...

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B. Mass Layers - Mass layers must be non-porous and limp for maximum effectiveness. Plywood and other stiff lightweight materials do not block sound as well because their stiffness properties allow them to trans- mit noise through sympathetic vibrations, i.e. the panel becomes a sounding board. Plastic sheets loaded with mineral compounds are the most common type of mass layer. These plastics have their best application in places where the mass layer must withstand high phys- ical abuse. Because of its high density and low stiffness, vinyl is one of the best noise barrier materi- als and is the...

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17 Lime Street Suite 1 Marblehead, MA 01945 1-800-359-1036 www.SOUNDOWN.com 3005 S.W. 2nd Ave. #102 Fort Lauderdale, FL 33315 1-954-761-9188 [email protected]

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Handbook of Noise Control Materials

Handbook of Noise Control Materials

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