Walk outside on a cold winter day just after the first big snowfall and you can hear the hush in the air. Everything sounds different because that hush in the air is the snow absorbing sound. Now, compare that to walking into a gym where the sound bounces around and lingers in the room.

When sound hits a material, three things can happen. First, the sound can be reflected; like in the gymnasium where it bounces off the hard walls and is redirected. Second, some of the sound can be transmitted through lightweight materials, like thin office walls. Finally, the sound can be absorbed. What happens to the sound when it is absorbed? It gets trapped in the material and converted into an extremely small amount of heat. Don’t count on it as a replacement for your heating system.

Materials that absorb sound are porous, like the snow. The air gets trapped in between the little snow crystals (or fibers in other materials) and turned into heat. One of the most common materials used to absorb sound is fiberglass. Closed-cell spray foam, on the other hand, acts as a good thermal insulator, but is a very poor acoustical absorber.

Just as not all materials are porous enough to absorb sound, not all materials absorb sound in the same way. Acoustical absorption is frequency dependent. That means two materials may look the same, but one might absorb high frequencies or high pitch sounds, and another may absorb mid or low frequencies. Typically, as the thickness of the material increases, so will the absorption of low frequency sound.

At ABD Engineering & Design, it’s our job to engineer acoustical solutions that control how the sound is reflected, transmitted, or absorbed based on the type of space. If maximum absorption were the goal, we’d treat every project like a movie theater or even like an anechoic chamber. But in the real world, different spaces have different acoustical needs, and our job is to develop acoustical solutions that are custom fit to meet those needs.

Melinda Miller

Melinda Miller brings her passion for all things sound and 20 years of experience to her role as Principal Engineer of ABD Engineering & Design. Her expertise includes diagnosing and preventing noise problems, designing acoustically optimized environments, and using evidence-based design practices. Melinda has consulted on projects involving architectural acoustics, noise isolation, mechanical noise control, and occupational noise exposure. Her experience includes higher education, K-12 schools, performance and worship spaces, healthcare facilities, industrial facilities, hotel and multi-family residential buildings. A Professional Acoustical Engineer, licensed by the State of Oregon, Melinda earned her Bachelor’s Degree in Mechanical Engineering from the University of Idaho, and Master’s from the University of Illinois, Chicago. She has continued her education and training, earning her INCE Board Certification (INCE Bd. Cert.), Evidence-Based Design Accreditation and Certification (EDAC), and LEED AP BD+ C. As an Assistant Professor of Acoustics for Columbia College, she taught undergraduate junior and senior level classes in HVAC design, vibrations, acoustical testing, building noise control, and musical acoustics. Melinda has chaired sessions on various topics at Noise-con and Inter-noise since 2013, and has served INCE as the Co-Chair of Building Acoustics Technical Activities committee, on the Certification Board, and the Board of Directors (2021-2024). Likewise, she has presented technical papers and education sessions for the Acoustical Society of America, the American Institute of Architects, and the Chicago Chapter of the Audio Engineering Society.

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