Acoustics and Standards: Sonic Serenity

An interview with Eric P. Wolfram, Riverbank Acoustical Laboratories
JP Ervin

It is easy to overlook the importance of sound. But whether you hear noise pollution from a nearby highway or the stomping of upstairs neighbors coming through your ceiling, unpleasant sounds can have a dramatic impact on your quality of life. I spoke about the field of acoustics with Eric P. Wolfram, laboratory manager for Riverbank Acoustical Laboratories and chair of the committee on building and environmental acoustics (E33). During our conversation, Wolfram spoke about the many industries that are affected by acoustics, why sound matters for everyday life, and what the committee is doing to support a rapidly growing acoustics market.

Q. When many people outside the industry think of acoustics, their mind probably goes to music. 

A. In the common vernacular, people will often think of the design of sound systems and loudspeakers. That is a field of acoustics, but what people are often actually referring to is the way sound behaves within that space. Basically, it is what happens between the loudspeaker and the listener’s ears – how sound reverberates, reflects, is supported by, or is impeded by that space.

There’s a lot that goes into that, especially the design of spaces that support listening functions within them. 

Q. Thinking more broadly, what are the other major areas that concern the field of acoustics

A. Acoustics refers to a broad range of activities. I’m most familiar with architectural acoustics. By that, we could mean the response of the space, reverberation, and reflections within a room, or sound transmission between rooms in a building. Other aspects of acoustics include industrial noise control: control of HVAC, heating mechanical systems, noise created by those systems.

Another is environmental acoustics and community noise. Structural acoustics and vibration. Signal processing and audio equipment, loudspeakers or electronic devices, how those sound. Psychological acoustics: human perception and reaction to sound, how we perceive and respond to sound and speech, generation of speech and speech pathology. Underwater acoustics, which is an interesting intersection of marine life and preserving whales and studying how noise affects them, but there are also military applications. Think sonar. Then automotive noise – vibration and harshness. Product sound quality analysis. The classic example is how the sound of a vacuum cleaner can lead someone to perceive it as more powerful.

Acousticians are people who work in the field of acoustics. They are also sometimes called acoustical engineers. We tend to specialize in one of these areas, but there are people who operate in multiple categories. Although these fields have the same underlying physics, each of these fields and industries have different adaptations and approaches to both testing and engineering within them. They’re almost like different ecosystems.

Q. One of the key focal points of the committee is on building acoustics. Can you tell me about this area?

A. When we say building acoustics, there are four areas that E33 focuses on. One is sound absorption, and what we mean is the ability of materials to reduce sound reflections and reverberation within a space. We have an entire subcommittee (E33.01) dedicated to this testing.

Our most famous standard is C423, which is commonly known as the NRC test. This property is not to be confused with airborne sound transmission loss, which is the property of a wall, barrier, door, or some type of partition to block sound from one room to another. Our most famous standard for this is E90, which yields the laboratory test and the sound transmission class (STC) calculation.

There’s a field version of this, E336, which is applied in field environments to ensure that condominiums and apartments pass building code requirements.

Another property is impact sound transmission, which is the ability of a floor-ceiling assembly to reduce footfall noise, most commonly in an above and below multifamily housing situation. There is also a building code requirement for this, impact insulation class (IIC) rating. Our test method, E492, defines how that test is conducted. That’s a laboratory test. There is also a field version of this, E1007. And then the fourth area is building mechanical systems. We have several standards related to measuring and controlling building mechanical system noise. And this is all in the E33.08 subcommittee.

Q. Another key area of the committee concerns “community noise.” What does that subfield refer to?

A. Community noise is also commonly referred to as environmental acoustics. It refers to the study of sound propagation in outdoor environments. For example, studying the impact of aircraft noise on residents that live near an airport. Common noise sources in outdoor environments would be highways, trains, aircraft, and maybe even outdoor industrial equipment. This noise propagates through the air, sometimes over relatively long distances. Measuring and reducing their impact on residences is a common field. We have a subcommittee dedicated to this pursuit, E33.09.

Q. From our discussion, sound seems to have a large impact on our lives, but it seems like something people could easily miss. Can you underscore why the field of acoustics is so important?

A. Acoustical engineers and designers commonly run into the situation where their recommendations for a building or an architectural space become value-engineered out or are perceived as being unimportant in the design stage. A good consultant will be adept at trying to communicate the necessity of these treatments and what the occupants can expect if the treatments are not applied. In the design stage, sound and acoustics might seem like a secondary priority. But when there is a noise problem in a space and you’re living with the problem, it is the number one problem in your life.

Let’s say you buy a brand new $2 million condominium. When you were shopping and looking at your different options, maybe you were thinking about how high the ceilings are, the finishes of the floor, the relative size of different rooms, and ‘Oh my gosh, I’ve got to have that kitchen!’ Then you move into this condominium and you realize that you can hear your neighbor walk across the condominium in both directions all day long. I’ve had experiences where people call our lab, literally in tears, because they’ve purchased a condominium, and they have this problem that they can’t live with.

Q. How do standards play a role in situations like that one or in helping the world more generally?

A. Awareness of acoustic concerns and noise considerations is rapidly growing. There’s a trend where individuals who maybe lived their whole lives in single-family homes are moving into a multifamily housing situation. Suddenly they hear their neighbors, and this is something they are not accustomed to. There’s growing concern about this issue. There’s also a concern with transportation noise coming in through exterior fenestration. New York City has been leading the way in increasing requirements. They are treating noise as an environmental hazard and something that needs to be mitigated through a remediation process. This growing awareness of acoustics is attracting a large number of new businesses and people into this space of acoustically-rated products and systems. From my point of view, as a lab manager, the number of businesses that sell products with acoustical performance ratings has multiplied in the past 10 years, possibly several times over, and I think it will likely continue to grow.

In addition to a large influx of new players, many of which don’t have an acoustics background, established acousticians are a notoriously independent-minded and opinionated bunch. It creates an interesting situation where there are many different opinions about how to perform a test, for example. The standards created by our committee are critical to ensuring that for test results or terminology that we’re using across hundreds of companies and maybe millions of residences around the globe, we’re all talking about the same thing. As industry improves their acoustical performance criteria requirements – and the enforcement those requirements becomes more commonplace – it’s critical that requirements reference our standards.

Q. What are some of the key priorities or developments happening in the committee right now?

A. We have a lot of new energy in the past few years, and we are continuously improving and growing. We are adapting existing standards for new categories of products and materials that didn’t even exist a decade ago. For example, C423 has a new Array-NRC rating for spaced-object arrays. We are also harmonizing processes and calculations across different standards. For example, adjustment correction for background noise is handled in the same way across different standards, which it wasn’t before. We are also improving the standards and expanding the standards used by engineers and consultants in the field. We are implementing and accepting new technologies in the test standards and the measurement methods, such as the measurement of decay times, with the impulse response method. And then we are establishing and improving the precision and bias statements across our standards with the intent to further improve the reproducibility of our methods.

Q. Acoustics is a unique field. How did you end up having a career as an acoustical engineer?

A. I have a bachelor’s degree in acoustics from Columbia College, Chicago. After I graduated, I worked for a consulting firm in Milwaukee called Scott R. Riedel and Associates, leading their acoustical engineering and field-testing operations. That firm is nationally known in the traditional worship space industry, spaces where choirs and pipe organs and classical music are an important sound source, with people singing together in the space. I really like well-balanced, reverberate environments. In 2012, I joined Riverbank Acoustical Laboratories as the laboratory manager. We’ve run about 1,200 tests a year for over 200 different product manufacturers. ■

Eric Wolfram is laboratory manager for Riverbank Acoustical Laboratories. He has over 19 years of experience in architectural acoustics, previously serving as a consultant in acoustical design and noise control engineering for Scott R. Riedel & Associates. Wolfram is also chiar of the committee on building and environmental acoustics (E33). He holds a bachelor’s degree in acoustics from Columbia College Chicago and is a full member of the Acoustical Society of America.

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