Acoustical Insulation Selection: How to Find the Right Material for Unwanted Sound
When consumers clamor for quiet products, it’s crucial to invest in the right acoustical insulation. Acoustical insulation comes in many forms and can help address excess noise, vibration and harshness (NVH) in a long list of industries, including the automotive, home appliance, and HVAC markets.
However, an acoustical insulation that can lessen road noise for automotive cabins may not be the right solution for a sink that will ping with every drop of water. There are a variety of factors that can dictate which acoustical insulation material is best for your needs.
The first step toward determining which acoustical insulation is right for your application is to identify how you plan to go about mitigating excess NVH. There are three different ways to address sound abatement:
- Creating a barrier
Sound is created when surfaces like automotive body panels or HVAC duct work vibrate at or near resonance. Even a stainless-steel sink will make a pinging sound when impinged with water. The offensive sound can often be eliminated by damping, which prevents the surface from vibrating at the unpleasant frequency. Damping can be achieved by changing the resonant frequency through either the addition of a heavy elastomeric material to the surface, or by applying a thin visco-elastic polymer protected with a dead soft aluminum foil facer called a Constrained Layer Damper (CLD).
CLDs perform under the principle that vibration made on either side of the constraining materials (a sheet metal surface and often a foil facing) are trapped and dissipated in a viscoelastic or middle layer.
Either method must be securely coupled to the vibrating surface. The damper reduces vibrations by a shear action of the elastomeric layer that converts the vibration into negligible heat.
Sound absorption does exactly that: absorb sound. The insulation actually mitigates or absorbs sound waves through energy transfer. When properly sized fibers are exposed to certain sound frequencies the interlocked fibers microscopically vibrate and create heat. This motion converts acoustical energy into thermal energy causing a reduction in sound. This transfer occurs on such a small scale that the heat generated is imperceptible.
Almost any fibrous material will reduce sound, but significantly better results are achieved when using a sound absorbing insulation that is specifically engineered to mitigate sound at the offensive frequencies. Sound absorbers are best suited for mid to high frequencies. Low frequency or “bass” tones are extremely powerful and cannot not be fully addressed unless the insulation is very thick.
Hard Surface Sound Reflection
Sound will reflect from any hard surface at the same angle at which it strikes the surface. Reflected sound is commonly known as an echo. When the characteristics of reflected sound are not discernible, it is simply called noise.
Noise reflection can be reduced by providing a pathway past a hard surface into a more acoustically absorbent core. Tiny holes in the surface allow some of the impinging sound to be transmitted into the core where it is mitigated. This technology was recently employed in New York’s newly renovated Museum of Modern Art where the stairwells are lined with wooden panels that have been micro perforated, resulting in a significant reduction in background noise.
Common Types of Acoustical Insulation
Once a basic understanding of the offensive noise is established, the number of material choices can be extensive. Below is a brief summary of some materials that can be incorporated into a variety of sound mitigation applications.
Damping materials come in many optional constructions from different manufacturers. Nitto has an extensive selection of dampers some that are branded under the Legetolex™ name. If space limitations are a concern, 3M has a thin viscoelastic damping polymer tape series called 112. An important point is that whatever your choice of damping material it must be intimately and completely bonded to the vibrating substrate.
Although any type of fibrous material, from ceramic or fiberglass to polyester felt, can absorb sound, the most common and specifically targeted acoustical blankets are lightweight compressible blankets made from specifically constructed non-woven fibers. These constructions are extremely effective at reducing noise, vibration, and harshness (NVH) in automotive, appliance, and HVAC applications.
One of the most common and well known acoustic blankets is 3M Thinsulate®. Although Thinsulate has been around for a long time and has a well-established name and global presence, other manufacturers have also developed acoustic specific products that perform very well. Aim Fiber Products has a few acoustical product selections based upon polypropylene fiber technology. The materials are naturally hydrophobic and offer a thermal insulative benefit.
For years, foam has been a “go to” sound abatement material. From foam-lined enclosure boxes to acoustical studios, people think of foam to address nuisance sound. Just like fiber blankets, a properly selected foam is crucial to achieve the best performance tuned to the situation. Density, cell size, and thickness can significantly affect performance. Simply adding a foam can often help, but for the best solution it is recommended to speak with the experts. JBC has been die cutting foam for years and is happy to lend assistance.
A composite insulation is the combination of discreet insulating materials into a system that offers a wider range of properties than any single material cannot perform alone. A good example is JBC’s TABshield insulation.
TABshield combines the radiant heat reflective benefit of an aluminum foil with the conductive thermal insulating and acoustical absorbing benefit of a fiber core. Acoustical performance can be further enhanced with the addition of micro perforations through the foil face. Even after micro perforating, the foil performs as an effective radiant heat shield. The tiny holes allow some of the impinging sound to pass beyond the hard foil surface into the fibrous core where it is absorbed. At the same time the fiber core helps to slow conductive heat transfer.
Select the Right Acoustical Insulation for Your Applications
It’s crucial to find an acoustical insulator that’s right for your application. The experts at JBC offer decades of experience in converting and precision die cutting acoustical insulation materials for a range of industries. Not only do we have relationships with multiple material manufacturers, we can also use our knowledge of technologies in multiple markets to identify the right insulation needs for both your application and budget.
Ready to find the right acoustical insulators? Contact us today to learn more about how we can help you with everything from material selection to design, production, testing, and more.