Reverberant Revelations

by Marcy Marro | August 1, 2022 12:00 am

As the pandemic wanes and we return to workplaces and social lives, we are reminded that quality aural environments are just as important to our well-being as good lighting and healthy indoor air. Two space types with particular acoustic concerns are open office spaces and restaurants, but the issues in these spaces and the array of solutions to create optimal acoustical conditions may be applicable to many other places where people gather.

Open office spaces have advantages that have led to the persistence of this design trend. They are more space efficient, increase access to daylight and views, and can increase interaction and collaboration. However, long before the current post-pandemic hesitation to return to the office, there was broad dislike of open office spaces. In addition to feeling exposed, workers in these spaces most often complain about the lack of acoustic privacy for calls and conversations, and difficulty concentrating on tasks due to distraction from background noise.

These concerns can be exacerbated by design trends, such as eliminating finishes like suspended ceilings and carpeting. While the post-pandemic redesign of workplaces may include more private offices, fewer desks and more collaborative spaces, many will still have some form of open plan workspace that demands a more thoughtful approach to aural comfort.

Restaurants can be challenging as the acoustical design needs to be balanced with the multimodal culinary experiences of patrons, business owners’ financial objectives, adequate working conditions for restaurant staff, and other factors. As the pandemic phase of COVID-19 ends, people find themselves back in noisy restaurants once again—full of diners close to one another trying to talk loud enough to be heard and understood, sounds coming from an active open kitchen, recorded/live music, etc. These noisy environments are exacerbated by the sound-reflective surfaces common in restaurants that are not efficient at controlling excessive reverberant noise buildup.

Excessive noise in restaurants can detract from the patron’s experience, making it difficult to follow conversations and potentially impacting their focus on the culinary experience. Excessive noise can also be harmful to the staff’s hearing when they are frequently exposed to high noise level. Adverse acoustical condition could also affect the business, as customers may not return to the restaurant or recommend it to others, and there may be a high staff turnover.

In designing open offices, restaurants and other gathering spaces, key acoustical principles such as sound absorption, isolation of airborne sound, control of vibration and structure-borne sound and reasonable background sound levels, should be considered. Sound absorption is one of the most critical and is often overlooked in these space types.

Designing sound absorption for good room acoustics starts with defining the various space types and the primary intended uses the facility will include. In offices, which spaces will support concentrated task work versus meetings, presentations, and collaborative work? In restaurants, will it be casual or formal dining, will the kitchen be open to the dining space, and will live or recorded music be performed? The answers to these questions will determine the optimal reverberation time for which each space should be designed. From there, it is important to account for the other factors that will affect room acoustics, including room geometry, space layout, expected average and maximum occupancy, and the proposed inclusion of hard or soft furnishings.

With the space and use type, and other factors in mind, the next step is the determine the appropriate quantity and placement of sound-absorptive materials to add to the space to achieve the desired reverberation time. This can be calculated with reverberation time measurements in the actual space, modeling with 3-D room acoustics software, or a desk study can be performed based on room dimensions and sound absorption of planned surface finishes. Once the required area of absorptive material is quantified, the designer can select the appropriate finish materials to meet both acoustic and aesthetic requirements. These are typically installed on ceilings or walls, and could include:

• Acoustical plaster
• Acoustical spray
• (Micro)perforated wood
• Perforated metal with sound absorptive insulation or lining
• Fabric-wrapped panels
• Stretch ceiling/wall products

It is important to find a good balance between sound-absorptive and sound-reflective finishes. If there is too little sound absorption in a room, this makes the room relatively too noisy as sounds will bounce back and forth between hard and smooth sound reflecting surfaces. As the reverberant sounds prolong for some time in the room, this can impede speech intelligibility as earlier utterances mask subsequent speech. Excess sound absorption in a room can make the space relatively too quiet. This could make occupants feel uncomfortable as they would easily hear their neighbors’ conversations in a quiet room, and experience this as a lack of privacy.

The acoustic design of gathering spaces, including open plan offices and restaurants, is critical to supporting positive occupant experience and employee health and wellness. After controlling for exterior noise intrusion, vibration, and background noise, the careful design for the quantity and placement of sound-absorbing material is important to creating the optimal acoustic environment tuned to the anticipated space type and usage. A little reverberation gives a space a lively vibe, creates an appropriate level of speech privacy and enhances certain uses such as musical performance, but too much reverberation results in a disruptive or even hazardous level of din.

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Alan Scott, FAIA, LEED Fellow, LEED AP BD+C, O+M, WELL AP, CEM, is an architect with over 30 years of experience in sustainable building design. He is a senior consultant with Intertek Building Science Solutions in Portland, Ore. Kimteri Kim, WELL AP, is an acoustical consultant with 22 years of experience and a senior consultant with Intertek Building Science Solutions in New York City. To learn more, follow Scott on LinkedIn at www.linkedin.com/in/alanscottfaia[1].

Source URL: https://www.metalarchitecture.com/articles/reverberant-revelations/

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