Acoustic insulation selection starts with understanding the sound source, path, and receiver. Engineers also need to know the basics about sound absorbers, barriers, damping materials, and facings.
Acoustic insulation absorbs, transmits, or redirects sound waves – vibrations in the air that pass through objects and result in audible sound. Noise, or unwanted sound, is measured in decibels and has a specific frequency distribution. Through material selection and custom fabrication, Elasto Proxy can create acoustic insulation that’s “tuned” to address the frequencies in your application. As this article explains, understanding some basics can help you to get the acoustic insulation that you really need.
Source, Path, and Receiver
For starters, you’ll need to understand the sound source – or sources. In other words, is the noise that you want to quiet produced by a bell, whistle, or loudspeaker – or maybe all three? Perhaps you’re trying to silence traffic noises, or reduce the rumble from an idling engine instead. Low-frequency sounds, especially those that involve vibrations, can be especially challenging. Yet there are solutions.
In addition to the noise source, you’ll need to understand the noise path. In short, how is the sound transmitted? In the case of a bell, whistle, or loudspeaker, the sound may travel through a building’s interior wall and then disturb the occupants of an adjacent room. With mobile equipment such as logging trucks and military vehicles, engine sounds travel from under the hood to inside of the cab.
The sound receiver is important to evaluate as well. For example, passengers on a train, bus, or airplane want to be able to hear themselves talk. Yet in sports cars, the audible rumble of a V8 engine can be a selling point. Typically, hospitals and classrooms need to be kept quiet. On a factory floor, some noise is expected as long as it doesn’t exceed regulatory limits.
Absorbers, Barriers, and Dampers – Facings, Too
Now that you’ve identified the sound source, sound path, and sound receiver, it’s time to determine whether you need sound absorbers, barrier materials, and/or damping materials. As their names suggest, these three categories of acoustic materials either absorb, block, or reduce noise. Typically, sound absorbers are used at the source and with the receiver. Sound barriers and noise damping materials are used at the source and along the path. Depending on your application, you may need facings, too.
Sound absorbers are made of acoustical foams, come in different thicknesses, and may have a specialized facing. Ideally, a facing material represents a “knob” that allows the acoustic insulation to “tune out” certain frequencies. Sometimes, however, facings are used to address environmental concerns such as heat, dirt, chemicals, and oil. Facings can even look like leather, but you’ll need to balance all of your non-acoustical requirements against the facing material’s acoustical properties.
Barrier materials can also meet standards like UL94 V0 for flammability. Often, sound blockers are made from extruded vinyl or acoustical foams. Sometimes, multiple facing materials are combined to meet complex requirements. As with sound absorbers, the application of a pressure sensitive adhesive (PSA) can make it easier for personnel to install acoustic installation in the factory or in the field.
Damping materials provide plenty of options, too. Sheets of extensional and constrained layer materials come in different sizes and thicknesses. Elasto Proxy can help you to select the right damping material – and the right absorbing or barrier material, too. Using our water jet cutter, we cut sheet materials with speed and precision. We can also layer materials to create custom insulation “sandwiches”.
Learn More About Acoustic Insulation Selection
Ready to learn more about acoustic insulation selection? Contact Elasto Proxy to discuss your application, and look for Part 2 of this series next week.