Sound Practices: Modern office acoustics require holistic sound management solutions

by Katie Daniel | June 6, 2016 3:07 pm

by Robert L. Marshall
The open-office concept has become increasingly popular in today’s workplace. There are many advantages to this approach, including increased opportunities for collaboration, greater space efficiency, and potential for an interactive energy that appeals to many current employees as well as prospective talent.

However, there are also challenges inherent in the open office plan. A number of workplace satisfaction studies—such as the “2013 U.S. Workplace Survey” conducted by internationally renowned architecture, design, and planning firm, Gensler, and the U.S. General Services Administration’s (GSA’s) 2011 “Sound Matters” report—have found workers tend to like the more modern open-office design as a whole, but background noise and lack of privacy consistently get low marks.(Visit www.gensler.com/uploads/documents/2013_US_Workplace_Survey_07_15_2013.pdf [1]and www.gsa.gov/portal/mediaId/172515/fileName/GSA_Sound_Matters_(Dec_2011)_508[2], respectively).

Poor sound management can have a very negative impact on both worker satisfaction and employee retention. Office productivity can drop off significantly when employees are able to clearly hear and understand nearby conversations. This translates into lost dollars, whether from lost hours of work or from the large investment needed to recruit and train new talent to replace employees that may have left for quieter shores.

Product innovation has resulted in a large and still-growing array of acoustic options architects and specifiers can use to create quieter, more sound-efficient spaces. Sound-absorbing ceiling and wall panels, acoustical insulation, and sound masking are just some of the tools available. Depending on the project budget and goals, there are a multitude of approaches, but no one product or system will solve all things on its own.

Creating a good acoustic environment takes a careful examination of the specific characteristics of the space. Any office has its own unique qualities and challenges, and what works in one corner may not work so well in another. An informed design employs a variety of techniques where appropriate to help create a pleasant, focused work environment.

The rule of three
Managing acoustics in an open-office environment takes a multifaceted approach using an integrated suite of different products and solutions. There are three major techniques—collectively known as the ABC Rule—to keep in mind with respect to acoustic design:

Absorb
One can specify ceiling, floor, and wall products that absorb sound waves, rather than allow them to ricochet around the space. It is important to look for high noise reduction co-efficient (NRC) ratings—an NRC of ‘0’ indicates perfect reflection, while an NRC of ‘1’ indicates perfect absorption.

Block
Products with high sound transmission co-efficient (STC) ratings and high ceiling attenuation class (CAC) ratings can prevent sound from passing through them. This helps prevent noise from one room from passing into another. STC rates how well a building partition attenuates airborne sound. A rating of 25 indicates conversation can be heard clearly through a wall, whereas ratings between 35 and 40 are at a level of privacy and anything above 60 is essentially soundproof. CAC measures a product’s ability to block sound. A rating above 35 is considered above average performance.

Cover
Using sound masking technology can further break up sound and allow employees to focus.

A little less conversation
Perhaps the most obvious distraction to employees is the noise coming from the conversations of others. In a space with no acoustical control, sound waves from discussions ricochet and bounce back and forth between the ceiling and floor, allowing them to spread out farther and farther around the office. Even conversations taking place 3 or 6 m (10 or 20 ft) away can be distracting.

On the other side of that, it is important for employees to be able to have private conversations in certain situations. Just as much as one employee at his or her workstation does not want to overhear the conversation of a colleague, that colleague most likely does not want his or her words to be broadcast around the office.

While it is impossible to eliminate that sound in an open plan, the goal should be to make conversations unintelligible to someone working nearby. If the sound is deadened, blocked, or masked, it morphs into innocuous background noise and helps achieve a level of both focus and privacy.

The most effective method for minimizing the spread of those sound waves and reduce noise is to use sound-absorbing materials in the ceiling and floor. This prevents the sound from bouncing around the space. Using high-density fiberglass panels on the ceiling and floor assemblies with carpeting or sound-absorbing tiles can help limit the spread of sound.

The more absorptive the materials on the ceiling and floor, the greater amount of sound is controlled. As mentioned, design professionals can look for products with a high NRC—a rating of 0.70 is considered minimum performance in an office application.

Another important technique used in many offices is sound masking—the introduction of highly engineered sound at specific frequencies into the office environment. Such systems employ very specifically tuned devices that emit engineered sound in strategic places in the space. This has the effect of interrupting the spread of other sound without becoming a disruption itself. Used in conjunction with passive design strategies like an absorptive ceiling, sound masking can be very effective to manage sound.

Air up there
Another common complaint in office spaces comes from noise emanating from HVAC assemblies. The mechanical system has an extremely important role in the workings of a building, but seldom is much thought given to the disruptive sounds it can make.

Quiet air-handling unit (AHU) madels are available, so it is possible to design a less sonically invasive HVAC system for an office. It is something to consider with the entire building team upfront if an owner or designer wants to try to prevent an HVAC noise issue before it starts. In most cases, however, heating and cooling systems are designed to meet parameters that have nothing to do with sound, so owners and designers are left with managing the noise after the fact.

One very effective technique is to strategically place high-performing ceiling panels directly underneath the AHUs. The fiberglass panels discussed earlier are excellent at absorbing sound waves that collide with them, but actually have little ability to block sound going through them.

Insulated panels can achieve that sound blocking and stop excessive air-handling noise. One can look for products with a high CAC rating. Generally, above 35 is considered ‘above-average’ performance, but above 40 should be sought when possible.

Contain and control
Another acoustic challenge that must be dealt with in an office environment is the transmission of sound between rooms. Sound, much like water, will find any tiny passage through which to move. This means a theoretically ‘soundproof’ ceiling with a small gap of 0.1 per cent in a ceiling space can reduce sound performance by as much as 25 percent. For context, within a 100-m² (1075-sf) ceiling, a vent of 0.1 m² (1 sf) has this capacity.

Most offices use an open-plenum air system, which means the air is being pumped into the space and needs to return to the air-handling system to be heated or cooled. The penetrations needed to accomplish that in most cases would create an opening much larger than 0.1 per cent of the ceiling and likely compromise the room’s privacy. However, even in this case, there are things that can be done to help bring the sound performance back up to a more acceptable level.

For example, chimneys can be built over the air returns to deny sound an easy pathway. Insulation and products with high sound transmission class (STC) ratings can also be added around perimeter walls, and gaskets and thresholds can be applied to doorframes. While no single product or technique may be perfect on its own, a combination of components and strategies can deliver the desired results.

Right-sized solutions
When it comes to acoustic design, the most important thing architects and owners can do is educate themselves on the needs of the space and work on a multifaceted strategy to achieve the best results possible. While a major part of any sound management strategy, a ceiling is not a monolithic structure made up of a single product. It can comprise multiple materials and products to achieve optimal performance. Further, different products and solutions can be used on the ceiling without sacrificing its uniform look.

As an example, most ceiling panels can be covered in a uniform high-performance laminate. The same laminate face can be applied to different ceiling products, so designers can use different types of panels where appropriate without sacrificing esthetics. To someone looking up at the ceiling, it would be impossible to tell the difference between the different types of panels used.

Before tackling a design, it is very important for architects and owners to have an appreciation of how important good sound design is to the effectiveness of an office space. Good acoustics do not just make employee productivity better—rather, they make it significantly better. This creates a case for spending more attention in design and budgeting to make sure acoustics is given its proper due. Owners want their employees to be as effective as possible, and a little sound investment can go a long way toward creating a productive work environment.

PROBLEM-SOLVING: SMALL CONFERENCE ROOM

Issue: Even with sound-absorbing ceiling panels with a good noise reduction co-efficient (NRC) rating, the small meeting room off the main office seems to echo and it is hard to have conversations. Cause: The ceiling may be doing its job absorbing sound, but with walls very close together, sound waves are bouncing back and forth between the walls. Solution: Some sound-absorbing wall panels could be employed to help better control the reflected sound in the room.

PROBLEM-SOLVING: OPEN OFFICE WORKSTATION

Issue: A number of employee workstations are located just below a noisy air-handling unit (AHU). The sound is a constant disruption for those working nearby. Cause: Even though sound-absorbing fiberglass ceiling panels were used in the space, they do not stop the noise from the HVAC unit about the ceiling from pouring through to the office below. Solution: Swapping out a number of panels below the AHU with higher-performance sound-blocking panels with a high ceiling attenuation class (CAC) rating will keep the sound above the ceiling and away from the workers below. The same face material can be used on the new panels to create a perfect match with the surrounding ceiling.

Robert L. Marshall is the technical services manager for CertainTeed Ceilings and a lifelong participant in the commercial ceiling industry. The product of one of world’s first acoustic ceiling contracting businesses (a company founded by his family in 1927), he has more than 35 years of experience in contracting, distribution, and manufacturing of such assemblies. Marshall can be contacted via e-mail at robert.l.marshall@saint-gobain.com[3].

Source URL: https://www.constructionspecifier.com/sound-practices-modern-office-acoustics-require-holistic-sound-management-solutions/

---