Sound Decisions: Designing for Acoustical ComfortSeptember 2015
by Rachel White
Over the course of our 30+ years in business we could count on two hands the number of renovations where acoustics played a major role. While we have occasionally been asked to provide sound isolation, on the vast majority of projects acoustics aren't even discussed. To some extent this makes perfect sense; after all, we aren’t building performing arts centers.
Yet in the past several months, three clients have asked us to address sound quality and control as part of their projects. In one case we are designing an in-house performance space; in the other two cases we’re incorporating sound isolation. Given our relative inexperience with acoustical design we have been very fortunate to work with Alicia Larsen, an architectural acoustics consultant at Acentech, on these projects.
I spoke with Alicia to learn how we can better address acoustical comfort.
Rachel: I’m somewhat embarrassed to admit it, but before we started working with you, I hadn’t given much thought to sound quality in homes. I suspect that many of our clients are in the same boat. Could you briefly explain what you do?
Alicia: I’ve been involved in the acoustical design of a really wide range of building types: everything from performing arts centers to schools, manufacturing facilities, and multi-family residences. Architectural acoustics comes into play any place where there will be noise in a confined space. There are three aspects you need to think about: sound quality within a room, sound isolation between spaces, and background noise, particularly from mechanical systems.
Rachel: We’re currently working with a client on the renovation of her condominium, and one of her key concerns is noise from an adjacent unit. Do you encounter this often?
Alicia: Sound isolation comes up frequently in multi-family buildings. I personally work on it quite a lot. In fact, I have at least five multi-family developments that I’m working on right now.
Rachel: When you consult on multifamily projects are you mostly brought in after there have been complaints, or are your clients thinking about sound isolation from the get go?
Alicia: We work with a lot of teams to specify effective sound isolation during design, whether it’s a new apartment building or conversion of an old building, like a mill, into residences. But we do see this issue come up after the fact as well. With smaller buildings, like a three-family house, it’s much less likely for us to be brought in during design. That’s when we hear about complaints after the fact, which is unfortunate because it’s much more complicated and costly to retrofit sound isolation than to incorporate it from the beginning.
Rachel: We mostly work mostly on older homes, and it’s pretty common for clients to ask for an open floor plan. Their house feels chopped up. The rooms are cramped and dark. But by taking down walls to improve flow and create visual connections you can also end up with a noisier environment, right?
Alicia: Open plans definitely present acoustical challenges but these aren’t insurmountable. Obviously it’s important to maintain acoustical separation between living spaces and quieter spaces like offices and bedrooms. Part of this is done by paying attention to how rooms flow and connect to each other. Think about where you put your doors. Doors are essentially holes in your walls, which even when closed don’t attenuate sound as effectively as walls do.
Rachel: Is there anything else homeowners can do to control sound besides paying attention to the acoustics of room layout and flow?
Alicia: Finish choices also are important. The trend in home décor is towards harder surfaces. But when you put these in large open spaces you create longer reverberation times. Sound builds up and lingers for much longer. In public spaces we often use acoustical finishes to control sound. There are acoustically absorptive materials covered by stretched fabrics—
Rachel: —you mean like those panels you might see in a school music room?
Alicia: No definitely not! The fabrics I’m talking about hardly even look like fabric. They look like wallpaper or painted sheetrock and are really beautiful. You don’t see these in homes much though, except some of my colleagues have them. In most cases you may not need specialty products in a home. Rugs, upholstery, simple curtains or shades—these can often control sound.
Rachel: Many of our clients are retired or looking towards retirement and call us in because they want to age in place. Limited mobility is obviously a top priority in these cases. But I’m also wondering about hearing loss. Are there things we should be doing from an acoustical standpoint when we’re working with people who want to age in place?
Alicia: That’s a really good question. We’ve done some work at assisted living facilities. Many of the residents are moving from single-family homes, so sound isolation is a concern. And of course public spaces need to be comfortable for those with hearing loss. I would say that in a single family home one of the biggest issues would be background noise from mechanical systems.
Rachel: Why is background noise a problem?
Alicia: As you lose your hearing, high frequencies degenerate first. So you won’t be able to hear conversation or music well, but you’ll continue to hear low frequency sounds, such as fan noise. If you’re of normal hearing you don’t often notice background noise, but for people with hearing loss background noise can really interfere.
Rachel: Are there things we can do to reduce noise from mechanical systems?
Alicia: Of course! There are many approaches that you can take depending on what type of system you have. One thing that you can do without redesigning the whole system is you can keep your airflow velocities low. Airflow noise—air passing through a damper or diffuser—often occurs at the same frequencies as human speech, and so it can interfere with speech intelligibility.
For those who are interested in aging in place, I would also recommend addressing low frequency background noise. Approaches vary based on the type of equipment you have. Often times you have to weigh your low-noise goals against other goals such as system efficiency, so a more customized approach is appropriate.
Rachel: Last but not least, you are an accomplished vocalist. What role has that played in your career?
Alicia: It’s definitely what got me, and many of my colleagues too, interested in the field, and it’s given me a strong appreciation of sound quality.
Rachel: So you aren’t the only singer or musician in the bunch?
Alicia: Gosh there are so many of us we could start a band!