I recently had the opportunity to interview Michael McCoy, Director, Architectural Systems, Focal Point for an article about sound-absorbing luminaires for an upcoming issue of tED Magazine, official publication of the NAED. Transcript follows.
DiLouie: How would you characterize market demand for sound-absorbing luminaires?
McCoy: Over the past several years, there has been a dramatic increase in market demand for sound-absorbing luminaires, which comes from multiple drivers. First, acoustics is now becoming more front-and-center in the design phase of projects, leading to increased interest in sound-absorbing properties of all architectural products. Next, acoustic specialty ceilings, specifically felt ceilings, are a fast-growing product category. Finding luminaire solutions that aesthetically coordinate with these felt systems is driving additional demand. Finally, the decorative nature of sound-absorbing luminaires, with their unique form factors and colorful housings, provides options for designers looking to create brand-forward and visually interesting spaces for their clients. Acoustic lighting was considered a niche market where only small players were active just a few years ago, but is now in the early stages of growth with many major lighting manufacturers trying to find their place.
DiLouie: What are the benefits of sound-absorbing luminaires?
McCoy: There are 3 primary benefits. The first, of course, is giving the luminaire a functional purpose beyond lighting by contributing additional surface area of sound absorption, leading to a more comfortable audible experience for space occupants. Second, sound-absorbing luminaires can come in many materials and colors, giving specifiers another avenue to elevate the overall look and feel of a space. Finally, given the increasing demand for felt specialty ceilings, sound-absorbing luminaires that leverage felt material can more seamlessly and aesthetically integrate with the ceiling plane.
DiLouie: Open offices are obviously a popular application, but are there others? What space design trends in open offices and these other applications are driving demand for more acoustic control?
McCoy: Sound management in open offices is certainly a major driver of sound-absorbing luminaires. In the modern office, we’ve seen a push towards collaboration and equality. We foresee that this design philosophy will continue to gain momentum when the majority of the population goes back to work, as most workplaces will be repurposed with a focus on collaborative activities. This means that walls, partitions, cubicles, and private offices will be reduced and replaced with low-profile desks and other office furniture that supports collaboration. Also, traditional acoustic ceilings have disappeared and open ceilings have become more prevalent. While appealing from a visual standpoint, these spaces have created new challenges related to confidentiality and acoustic comfort. It’s often hard to hear people on conference calls due to echoing, it’s distracting to hear co-workers on the phone with customers, and private conversations are a challenge. All of these factors drive demand for sound management techniques.
As for other market applications, learning environments, specifically classrooms, lecture halls, and even office training rooms require a minimum level of speech intelligibility. In fact, there exists a Minimum Acoustic Performance prerequisite that applies to schools under LEED Building Design and Construction requiring core learning spaces to achieve target reverberation times (or a reduction in echoing), thus maximizing acoustic comfort. Both WELL and LEED offer points and credits, respectively, for achieving target reverberation time requirements for an array of other applications, including fitness facilities, music performance spaces, courtrooms, libraries, among others.
DiLouie: What are the basic fundamentals of acoustics? How is noise measured, and how is noise reduction measured?
McCoy: Three things can happen to sound as it moves through a space or medium: it can be reflected, transmitted, or absorbed. The “ABCs” of sound management can help specifiers achieve target acoustic objectives, where the “A” stands for Absorption, “B” is for Blocking and “C” is for Covering up. Each of the ABCs has its own purpose and can be measured in different ways.
The A, sound absorption, is primarily used to help reduce reverberation time, or echoing, in a space. Reverberation time (RT60) is the amount of time it takes sound to decay by 60 decibels. The higher the RT60 value, the more echoing. Good sound absorbers reduce the RT60 value and can come in the form of wall panels, ceiling tiles, baffles, carpeting, and other absorptive materials. The most useful metric for evaluating the effectiveness of sound absorbers is Sabins, which is the amount of sound absorption per square foot of material. Noise Reduction Coefficient (NRC) and Sound Absorption Average (SAA) are also useful, but they have limitations when comparing three-dimensional objects. Most architectural products are tested in a 3rd party laboratory for their absorptive properties. This is accomplished through a before and after test where the products are placed in an echo chamber. Given the reduction in echoing, or reverberation time (RT60), the Sabins of absorption can be calculated. The information is then presented in an ASTM C423 test report, which is used by acousticians and manufacturers to help specifiers with the design of their spaces.
The B, sound blocking, is intended to manage noise by stopping sounds from traveling from one area to another. In interior environments, typical sound blockers include cubicles, privacy dividers, office doors, acoustic curtains, ceiling panels, and walls. Blocking is also important between spaces and for keeping outside noises, including traffic noise, from entering the environment. Blocking, in principle, lowers sound transmission and is measured by Sound Transmission Coefficient (STC). Many spaces have Noise Criteria (NC) requirements which can be measured via background noise measurements in decibels.
Finally, the C, covering up, which is better known as sound masking, is typically achieved with the use of an ambient sound emanating from a speaker, similar to the sound of airflow, that’s specifically engineered to cover up human speech. Unlike sound absorption and sound blocking, both of which are intended to lower overall sound levels, sound masking does not eliminate sounds or eliminate speech noise – it increases the overall sound level. Sound masking elevates the sound floor enough to maintain speech confidentiality and mask distracting noises. There are two different types of sound masking techniques: indirect and direct. The indirect method is the most common, which uses indirect speakers evenly dispersed throughout a space to turn intelligible, distracting speech into unintelligible, non-distracting background noise. The direct method is more technically complex. It has the advantage of varying the intensity and frequency of each speaker to create zones within an office or to ensure a smoother transition from a quiet space to a louder space. In principle, masking reduces how far away conversations can be heard and understood by others, which is called the radius of distraction.
DiLouie: What are typical noise levels in say a typical open office, what is an ideal level, and what impact can sound-absorbing luminaires have? Do any building standards provide guidance, and what do they require?
McCoy: First, we must differentiate noise level, which is typically associated with background noise level, measured by Noise Criteria (NC), from what sound-absorbers, including sound-absorbing luminaires, are intended to contribute to in an environment.
Noise Criteria (NC) is achieved primarily through sound isolation, ensuring that there is adequate sound blocking material between spaces. Most open offices, if they do have NC requirements, are usually in the 30-40 dB range. However, sound-absorbing luminaires are intended to reduce reverberation time (RT60) or echoing in a space and are thus not intended to impact NC.
Ideal reverberation times can vary based on the environment and sound-absorbing luminaires can directly contribute to achieving better reverberation times. WELL and LEED both specify reverberation time requirements for a variety of spaces. WELL requirements are limited to conference rooms, classrooms, lecture halls, fitness facilities, and music rehearsal spaces while LEED is more exhaustive. For open offices, LEED offers Acoustic Performance Credits if a target reverberation time of < 0.8 seconds is achieved.
Even though these standards exist, specifiers may want flexibility to either dampen sound further in open offices, especially if private workspaces are more prevalent, or they may want to maintain more space vibrancy. Outside of LEED and WELL, the standards act as a good starting point, but the space should still be optimized based on purpose and the environment the specifier wants to create.
DiLouie: How are sound-absorbing luminaires constructed? What materials do they use, and otherwise how do they absorb sound?
McCoy: The effectiveness of sound absorbers results from a combination of 1) the material’s properties and thickness, 2) the amount, or surface area, of the material and 3) how the material is applied to a product or to a space.
In general, softer and/or porous materials absorb sound energy better than hard materials. Additionally, the thicker the absorbing material, the more absorptive it is. Therefore, to build a sound-absorbing luminaire, leveraging foam, recycled polyester, wool or perforated hard materials is a good start. Thickness variances can be a trade-off as thicker materials absorb more sound but can become more intrusive or appear clunky in the space.
The next variable is surface area of material. In general, the more material a sound-absorbing luminaire has, the better it will absorb sound. This is especially true if the product is functional in nature and spaced 8’ or 10’ on-center in a space. A small wool cylinder will have a minimal impact in this type of application, but a large dome may have a profound impact. However, if the small wool cylinders are used in clusters, they can be impactful as well. One of the major benefits of applying material to a luminaire is the that the material coverage is typically not on the horizontal plane, rather on the vertical plane. For example, a 2-foot tall baffle can have a comparable impact to having a 2-foot wide absorber, but still maintain an open, airy environment.
Finally, and perhaps most importantly, the effectiveness of a sound-absorbing luminaire depends on how the material is applied and how the luminaire is constructed. The best example of this is if we take a standard aluminum luminaire and adhere soft material directly to the aluminum. Even though there is no exposed aluminum, the majority of the sound energy will pass through the soft material, bounce off of the aluminum, and bounce back into the space. On the other hand, if we remove the aluminum from inside the luminaire, any sound that is not absorbed will pass through one side of the luminaire and likely get absorbed on the other side of the housing. This air gap can help improve absorptive properties by two to four times. This demonstrates that product design, not just the material or surface area, has a dramatic impact on sound absorption.
DiLouie: When evaluating and comparing sound-absorbing luminaires, what do distributors need to know to be able compare products, match them to an application, and confidently recommend them to a customer?
McCoy: For any given project, there may be lighting, acoustic performance, budget, and aesthetic requirements that need to be considered. While distributors have experience with meeting budget and lighting requirements, aesthetic and acoustic considerations need to be added to their decision-making criteria.
Starting with aesthetics, sound-absorbing luminaires typically have a unique housing material that will need approval from the specifier. The primary aesthetic drivers are form factor, material color, and material feel. If multiple manufacturers are used for any given project, the likelihood of mismatching colors is high, even if they’re specified with the same “book color”. This is primarily because, in the textile world, different batches of the same material can yield slight variances that are very noticeable in the space. The recommendation would be to use the same manufacturer for any specific color or look to ensure continuity in design.
Acoustic performance is the other area to consider when comparing products. If the primary driver for the use of sound-absorbing products is aesthetics, then this may not be an issue, and this should be validated with the specifier. If acoustic performance is a primary driver or a requirement, then a thorough understanding and analysis of products is required, which would require input from the manufacturers, specifiers, and, potentially, acoustic evaluations by acousticians.
Because every product is constructed differently and uses different materials, architectural product manufacturers looking to add absorption to a space need to have their product evaluated by a third-party laboratory. ASTM C423 test reports should be available to support sound absorption claims.
Two-dimensional products, like wall panels and carpeting, can be evaluated using Noise Reduction Coefficient (NRC) values. In general, the higher the NRC, the better the absorption qualities. However, for three-dimensional products, such as acoustic luminaires, a single number product comparison like NRC is not the correct approach. For example, if the specifier wants to use acoustic linear baffle luminaires, the absorption per luminaire will vary based on how many luminaires are in the space. This means that if acoustic luminaires are spaced 4’ apart or 6’ apart or 8’ apart, the sound absorption properties per luminaire will change. Therefore, a single number on a manufacturer spec sheet is not effective and the distributor would need to be armed with the correct ASTM C423 test data for how the product is used. As we can see, this is not a simple endeavor, so the distributor should rely on the manufacturer or on an acoustician to provide support to validate the effectiveness of the product in the space.
DiLouie: What is an ideal sales pitch for sound-absorbing luminaires? Are there any simple, effective ways distributors could demonstrate the utility of a sound-absorbing luminaire firsthand to a customer?
McCoy: In recent years, the design community has recognized that there is a need to consider sound management techniques earlier in the design process. Since lighting is literally a “fixture” in every interior space, it makes sense that designers would leverage the luminaires’ surface area to help absorb sound. Additionally, when the sound-absorbing luminaire is specified early in the design process, the designer ensures a cohesive aesthetic between the luminaires and the other architectural components.
Moreover, selecting a sound absorbing luminaire or integrated acoustic ceiling a lighting system simplifies the specification, sourcing, and installation process over integrating non-acoustic architectural luminaires from one manufacturer with acoustic baffles or ceiling systems from a different manufacturer. The resulting aesthetic is likely to be superior and the logistics simplified.
Manufacturers can provide many tools for the distributor to demonstrate the utility of the luminaire, from simple acoustic calculators or rule-of-thumb approaches to detailed ASTM C423 test reports for side-by-side product comparisons and advanced calculations. Good manufacturers who are serious about lighting and acoustics will also provide layout and lighting calculation services to assist the distributor and the designer.
DiLouie: What can distributors do to position themselves to sell these products?
McCoy: Distributors are seen as go-to experts for lighting designers, engineers, and contractors on technical lighting requirements. Sound-absorbing luminaires, given their acoustic impact and differentiated aesthetic, require distributors to reach further upstream in the interior architectural design process. Developing relationships with key decision makers, including architects, interior designers, acousticians, and ceiling contractors, and acquiring a basis of knowledge around architectural acoustic materials and the technical aspects of sound management will help distributors gain a stronger market presence and help hold projects downstream.
DiLouie: Are there any tradeoffs or pitfalls that must be mitigated?
McCoy: Once a sound-absorbing luminaire is on spec, the distributor will have to consider more than just the lighting requirements in order to substitute a competitive product. Most sound-absorbing luminaires leverage materials that need to be batched or color-matched properly. If not the end result could be materials that are inconsistent with the original specification and may clash with other ceiling or architectural elements. Additionally, if the design requires a certain amount of sound absorption, the distributor must be careful to perform accurate side-by-side product comparisons before substituting. Either of these cases may require input from the designer and the manufacturer to ensure the requirements behind the specification are being met.
Other potential tradeoffs and pitfalls include a higher cost relative to an equivalent non-acoustic product, more considerations regarding cleanability and handling during installation, and better coordination with ceiling contractors if the acoustic luminaire is a component of a broader ceiling installation.
The benefits of creating a more comfortable, brand-forward, and coordinated interior space outweigh these potential concerns.
DiLouie: If you could tell the entire electrical industry just one thing about sound-absorbing luminaires, what would it be?
McCoy: As a trade, related to technical lighting and installation, there’s not much difference between sound-absorbing luminaires and standard aluminum fixtures. The big difference between the two is acoustic impact and aesthetic. In order to sell and coordinate the sound-absorbing luminaires, a new set of tools, knowledge, and relationships may be required to most effectively deliver the best solution to the market.
DiLouie: Is there anything else you’d like to add about this topic?
McCoy: The electrical industry should use caution when it comes to claims regarding the acoustic impact of sound-absorbing luminaires. Sound energy and how it travels through or reflects off of different media is a complicated topic. Manufacturer data and acoustic calculators can directionally help designers understand the impact of sound-absorbing luminaires, but for exacting space requirements, including designing for WELL and LEED projects, professional acousticians should be leveraged to validate the effectiveness acoustical products in a design.