Using Acoustical Management Materials to Control NVH in Your Application
Acoustic management is the process of dampening, insulating, or controlling noise, vibrations, and harshness (NVH) generated by any structure, machine, product, etc. What was once mostly focused in automotive and aerospace has become a common practice in the design of products in many industries, including HVAC systems, watercraft, commercial vehicles, electronics, medical diagnostic devices, home appliances, and many others.
Depending on the application, acoustic management is generally needed for one (or more) of three reasons:
Making a safer environment for workers or consumers.
Designing and manufacturing products that are more comfortable to use.
Decreasing vibrations that can damage or weaken products, machines, etc.
Acoustic management is a critical component of the design of any product and should be considered in the initial design. By using a variety of acoustic management materials, product designers and manufacturers can reduce and modify NVH to safer and more manageable levels, leading to many benefits:
Better product longevity and durability: even small vibrations can weaken components over time, loosen bond joints, and create other issues that reduce the lifespan of products.
Products that project high quality: by reducing NVH, products are much more comfortable for consumers to use and project quality. Acoustic management can reduce the noise generated by appliances, make cars and buses quieter on the interior while also minimizing the sound emissions outside the vehicle, reduce the sounds made by boat engines, decrease constant vibrations made by fans or other moving parts, etc.
Safer products that meet safety standards for workers and consumers: OSHA standards and other regulations dictate that industrial environments must not exceed certain sound levels. Reducing NVH helps employers stay in compliance with the machinery and other devices they use.
Certain types of acoustic management materials also provide added benefits, including:
Thermal insulation
Flame retardancy
Resistance to outdoor environments and chemicals
Low moisture absorption
Easy application: the materials can be provided in slit rolls or die cut parts
How Acoustic Management Materials Help Control Sound
Although acoustic management materials don’t eliminate NVH, they play a large part in controlling them and keeping them at manageable levels. The materials actively work to absorb NVH, isolate it, or reduce it at its source.
There are two types of noise that these materials help control:
Structure borne noise (vibrations)
Air-borne noise
Structure borne noise is defined as mechanical vibration energy that is generated by a product or machine. This noise travels through the actual structure of the product and any materials it is in contact with. Acoustic management materials reduce structure borne noise and vibration energy by dampening and dissipating it at the source. The materials prevent the actual structure from vibrating, constraining the structure borne vibration energy and converting it into heat energy. Some materials can also be used to isolate the structure borne noise and vibrations, preventing them from travelling to other parts of the product.
Air-borne noise is the result of the interaction between a vibrating surface and the surrounding air. These vibrations create harsh sounds— buzzing, squeaking, rattling, and other audible noises— that acoustic management materials work to dampen and control. There are three different ways to reduce air-borne noise: absorbing it, blocking it with a barrier, or adding layers of materials to dampen it.
Acoustic Management Material Options
There’s a wide range of products that provide the required level of NVH control in a given application. While certain pressure sensitive foam tapes can be used to dampen NVH and improve performance (all while simplify the manufacturing process), there are materials that are highly suited to controlling resonant vibration and reduce structure and air-borne noise. Acoustic insulation absorbs noise in a wide range of frequencies and also provides a noise barrier. Sound damping pads and films are often used in metal and composite panels and supporting structures, and these materials (PSA tapes included) can be provided in slit rolls or custom die-cut parts to suit your specific needs.
About Nonwoven Acoustical Insulation
Nonwoven acoustical insulation is made from Eglass Fiber, polyester fiber, or polyester/polypropylene. These are lightweight materials (between 0.09 and 0.14 lbs./ft2) with menial thickness (between 0.25 and 1.6 inches) that provides very high acoustic absorption and internal integrity. Scrims, foils, and other composite materials can be added to improve insulation performance while reducing thickness. Often used in vehicle trim acoustic treatments for door panels, HVAC sound absorption, instrument panel sound absorption, nonwoven acoustical insulation is ideal for more demanding applications that feature extreme temperatures. Its dampening capabilities are fair when compared to sound dampening pads, but their sound absorption capabilities are very good. The material is also highly malleable—it can also be folded, bent, and scored without cracking—and, if needed, provides some thermal insulation, as well. 3M™ Thinsulate Acoustic Insulation SM600L and 3M™ Flexile Acoustic Material FAB Series products are acoustic insulators that absorb and provide a barrier to low and high frequency noise.
Nonwoven acoustical insulation has:
High flame resistant: UL 94V-0 flame class rating
Good thermal Insulation at 75°F
Excellent dielectric strength
Low moisture absorption (<0.6%)
High chemical resistance
Sound Dampening Pads
Sound dampening pads are heavier than nonwoven acoustical insulation, but they attack noise at its source by reducing or eliminating vibration. Sound dampening pads reduce sound at the source, rather than trying to absorb it, which results in much quieter operation and better vibration dampening. They come in many different material types that can be die cut into custom shapes, and are also available in a variety of different colors, thicknesses, etc. These pads come standard with PSA tape for easy peel and stick application. The viscoelastic nature of the base polymer absorbs energy generated by vibration. Sound dampening pads are often used in file cabinet doors, metal enclosures, truck liners, vehicle side panels, and fan housings to name a few.
Material thickness and quantity required will depend on the product. Some commonly used products include:
3M™ Sound Deadening Pads 8840: made from bitumen, mineral filler, elastomer
3M™ Damping Foil 2552: made from aluminum foil backed with acrylic viscoelastic polymer