As consumers, we know there’s nothing worse than a noisy product. But as manufacturers, we also understand that ensuring our product’s functionality is the number one priority during production.
When it comes to acoustic issues, electronic products are held to a high standard. Computers, phones, servers, and other similar products are all expected to run quietly to provide a positive user experience. To accomplish this, manufacturers use a multitude of materials to contain and reduce acoustics. But how do you decide which material to use for your product? That’s where this guide comes in.
In this blog, the experts at Mueller will take you through some common sources of sound emittance, materials used to reduce or contain noise and which of those materials is best at its job. By the time you finish reading this guide, you will have the knowledge to make a better material selection regarding containing and reducing unwanted sound in your electronic products.
Common Sources of Noise in Electronic Products
Electronic products have plenty of moving parts, which means there are numerous opportunities for noise to be created. According to our expert on the topic, Steve Mitra, there are a few key components, common to most products, that generate the most interference. He told us that cooling fans, motors, valves, exhaust ports, and moving parts generally produce the most noise in electronic products, to varying degrees.
Motors are the most prominent source of noise, as they create both sound and vibration, which is an additional source of interference. Generally, motors produce low-frequency noise, which can result in rumbling or humming noises. Cooling fans can produce low-frequency noise at their slowest speed but grow in frequency as they spin faster. Valves also create mid-to-high frequency interference as they open and close.
These sound emitting sources will all produce some noise, but there are ways to minimize and contain their effects in your products.
What Materials Reduce Acoustic Interference?
Before getting into specific materials that reduce interference, it’s important to cover the categories that these materials can fall under. According to our sound expert, there are four categories of materials that can reduce acoustic interference in your products. These categories are isolation, dampening, absorbing, and barrier materials, all of which have different effects on a product’s acoustics.
Let’s break those categories down. Isolation materials are those that are put between the sound source and what it’s installed to, acting as a gasket. Dampening materials are those that are put on a sound source, such as a motor, to make it heavier and quieter. Absorbing materials are constructed to soak up sound and stop it from escaping, while barrier materials reflect sound in order to limit its transference.
With these categories in mind, let’s look at what materials are specifically used to reduce acoustic interference.
The most widely used material for acoustic interference control is polyurethane open-cell foam. This material is versatile, resistant to dust and debris, and cost-effective. Open-cell foams can be treated to increase their moisture, mold, flammability, and UV resistance. With the ability to be cut to fit any shape or size foam has been used for many years to reduce sound in electronic devices.
Other common and effective noise containing materials are nonwovens which can be made from, amongst others, fiberglass, polyester, polypropylene, and cellulosic fibers.
These various fiber nonwovens can be custom designed for specific applications in to perform in specific surroundings. The fibers can be treated to add material characteristics such as moisture, mold, flammability, and UV resistance. Nonwovens can easily be die cut into specific size and shapes.
The Best Materials for Reducing Acoustic Interference
Like many instances in the manufacturing world, the best material is going to be what directly addresses a specific product’s needs. However, there are some materials that have benefits or drawbacks that set them apart from the rest. While it isn’t possible to give a definitive ranking of materials, we can examine which is the best choice for your next product.
Mitra says that when deciding on the best material for containing and reducing noise in your product, the best product will be the one that is “effective, inexpensive, holds up in the surroundings and meets any regulatory requirements.” Keeping this in mind, let’s compare some of the materials listed above.
As stated earlier, open-cell foam is probably the most widely used material for sound reduction. Open cell foams are relatively cost-effective sound absorbers that offer a barrier to dust & debris penetration when under compression. However, these foams do have some environmental limitations. Specifically, polyester type foams are subject to degradation when subjected to moisture and/or UV exposure. Open-cell foam also may need to be treated to meet the certain needed flame-resistant requirements. With all this in mind, open-cell foam is a good choice for products that are used in a contained surrounding.
Fiberglass may be open-cell foam’s main competition in the cost-effectiveness category. It can be a good choice for outdoor electronic products since it excels as an insulator, inherently fire-resistant and stable under harsh conditions. Many homes are still utilizing this mature material in wall insulation applications today due to its overall performance. Fiberglass’ key limitation is that it is an irritant, making it a poor choice for products that are regularly handled or where the fibers could become easily dislodged.
Polyester, polypropylene, and cellulosic fiber nonwovens are very versatile sound reducing materials. They work for both indoor and outdoor electronic products, as they can be resistant to most environmental conditions while providing sound reduction. While they can be more expensive than other sound absorbing materials, the difference can frequently be offset by increased performance.
With all these materials, however, there is one other key factor that could influence your decision and that is the utilization of weight and thickness to custom design a material for a specific application.
According to Mitra, “If there’s a polyester nonwoven and open-cell foam and both are equal in density and thickness, typically the polyester will have a lower noise reduction coefficient. But if the foam is 2-inches and the polyester is still 1-inch, the foam will outperform.” In general, the heavier and thicker materials perform better than a lighter and thinner material. Electronic devises are becoming smaller and smaller and the producers must have room to accommodate sound absorbing materials. Therefore, thin materials with specifically designed densities are being used. The density may be tailored to absorb sound within targeted ranges and frequently performance increased by using acoustical facings. An additional benefit of the facing may be to increase flammability or provide a barrier to air and water.
Choosing the Right Material
Ultimately, whatever material you choose will be decided based on the specific needs of your electronic product. Acoustic interference can come from a number of sources, but there are just as many materials out there to counter the effects of those sources.
Mitra says that the first step to reducing sound is to prevent it. A good example is to add mass to a sound emitting source to dampen it, While this is true, the materials we’ve discussed in this blog will help you reduce the interference caused by a noisy engine, cooling fan, set of valves, or any other noise source.
With this guide, you now have a basis to begin the selection of materials to address your electronic sound devices’ sound reduction requirements.