People want to work and live in quiet spaces, but that isn’t always feasible in a busy building nestled in a noisy city. The desire to tune out unwanted sounds means that building managers face countless complaints and risk losing tenants. In residential buildings, they are confronted about that upstairs neighbor with loud footsteps, that gym with thudding barbells, or that essential but noisy building equipment operating at all hours of the day. In commercial buildings, these complaints often involve lack of speech privacy or poor acoustics in conference rooms or distracting noises that affect workers’ productivity. Beyond comfort, according to the World Health Organization (WHO), noise is the second-largest environmental cause of health problems, just after the impact of air quality.
I work at Cerami Site Assessments, a division of New York-based Cerami Associates. We help property and facility managers solve noise issues to create happier tenants. We have been in the acoustic design and technology business for over 50 years but we have recently decided to grow our site assessment due to high demand: NYC noise complaints reaching all-time highs.
An Iterative Process
It is important to start any solution to excess noise with a discussion to understand the details of tenant complaints. With that completed, the next step is to look at any noise level criteria that needs to be met such as noise code requirements, lease language, or construction specifications. With all this in mind, the next step is to conduct a thorough evaluation of the space, monitoring and measuring the sound and vibration levels using specialized equipment. After a thorough assessment, it becomes time to consider the acoustical performance of the construction between spaces and evaluate the room acoustics to see how sound moves in and through a space.
An examination of the mechanical equipment, such as loud air conditioning equipment, pumps and elevators is also important. Working with the property’s building engineer, a consultant can assess not just the equipment but also the mechanical space in which it lives. What adjustments can be made to dampen the sound or adjust its path? Often the solutions must be carefully planned to help ensure that equipment critical to the function of a building can be treated while minimizing downtime.
Each occupied building has its own unique challenges for performing assessments of a given noise or vibration. It may be necessary to work at night when office tenants are not in the building or during the day when a residential tenant is at work. Engineers can also install longer-term monitoring equipment to record and measure noise or vibration levels that may be less predictable. Sometimes several visits may be required to discover the noise source(s) and develop a set of sensible solutions.
Types of Sounds
Noise mitigation engineers consider how the noises are produced and transmitted and make recommendations from there. Airborne sounds are generated in a space and transmitted through the air while structure-borne sounds are generated in and transmitted through a solid such as the structure and materials of a building.
Airborne sound transmission can be mitigated by reducing the noise generated at the source, such as a fan, or by adding sound-absorbing finish materials to the room where the source is located. Owners can also enhance the construction that separates the noise source from adjacent areas, by increasing the mass of the construction, increasing and/or insulating the airspace in the wall or ceiling cavity, or a combination of the two methods.
Structure-borne noise transmission can be reduced by eliminating rigid mountings or contact. Equipment can be modified through adding vibration isolation mounts where it is supported from the structure. Footfall noise is another example, where the use of carpet and padding is the most effective treatment. Resilient underlayment mats placed beneath hard floor finishes can reduce but not eliminate this type of noise transmission.
Identifying the Source
While it is important to consider the legal requirements for maximum noise levels, ultimately the aim is to make recommendations that result in peaceful enjoyment of a home or work environment. The process begins at the source, by working to reduce the noise at that location. Next, recommendations can be made to reduce sound transmission out of the room containing the noise source.
The source can be a piece of equipment beneficial to the operation of a building, such as an exhaust fan. Sometimes, however, the equipment may be operating at a higher capacity than is required. Therefore its speed could be reduced to result in lower noise output while maintaining adequate service to the building. Sometimes one can’t change anything about the noise source, so the path of transmission must be considered for treatment. Generally, acoustical treatment is more cost effective the closer it is to the noise source. Within the affected tenant space, noise mitigating treatments may be less effective, more expensive and prohibitive due to space constraints.
On the facilities side, speech privacy and sound quality are more the issue than noise disruptions. Private offices and conference rooms with glass partitions are beset by issues related to sound between spaces as well as poor sound quality. Audio conferencing can become difficult when reflected sounds muddy speech intelligibility. Use of sound absorbing finishes and improving the sound insulation properties of the partitions between rooms can help to improve these issues. Additionally, introducing sound masking systems or “pink” noise in an open plan office is helpful in making other conversations less intelligible and office sounds less distracting. However, this practice is not advisable in conference or meeting rooms where people need to hear each other clearly.
From there it is important to use the data to look at options, often ranked in terms of cost-effectiveness. The key is to understand what you are trying to achieve while keeping cost in mind. For instance, the costs involved in achieving a standard of inaudibility are much higher than meeting minimum code requirements. Considering the costs that are often involved in remediation, it is critical to understand the problem, criteria, and paths of transmission so that the owner can target resources wisely.
Remember, the costs can add up quickly. It is often more expensive and more difficult to treat noise issues after someone has constructed the space and moved in. There is also the cost of working around occupants to get fixes implemented in addition to the cost of trying to retrofit existing conditions. Residential noise complaints are often the toughest because people are so personally invested. Often the person has had to endure the noise for months or years by the time a consultant is called in. The challenge is often that they are so sensitized to a noise that is completely new to an outside party.
Generally, the report provided by a noise remediation consultant is handed off to a contractor who can implement the solutions. For bigger challenges, other design professionals may be needed to provide further integration of the solution and help ensure, in the case of essential building equipment, that the treatments won’t adversely affect its operation.
Here’s an example of the noise remediation process at work: we was hired by a commercial property owner who had a very important and very unhappy office tenant located directly above a major mechanical room. Complaints of a tonal noise that affected productivity had to be remedied. The owner had to discount the rent of the tenant for a long period of time while they tried to find a solution, losing key revenue due to disruptive sound.
Our site assessment determined that the strong tonal noise was caused by the operation of several pumps. The acoustical criteria in this case were maximum noise and vibration levels contained in the tenant’s lease. Baseline readings were taken, and several treatment options were presented in rank order to the owner that ranged from installing more effective vibration isolation of the equipment and connected pipes, to installing variable speed drives on the pumps. After several attempts by the team to perform targeted isolation of pipes and conduct multiple subsequent noise and vibration measurements, the recommended variable speed drives were eventually installed. This allowed the pumps to be operated at a reduced speed most of the time, eliminating the tonal noise and vibration, and effectively meeting the lease requirements.
One of the latest problem-solving technologies to limit noise is virtual reality acoustic simulation. A client can enter a VR booth and step into their space in order to hear what their customers hear. For example, a restaurant that is currently designed with entirely sound-reflective surfaces can be a very noisy experience for customers. VR technology can simulate that environment and reproduce all the sounds—music, patrons talking, open kitchen bleeding noise. Wearing a VR headset the client can experience the restaurant as patrons currently experience it and how that experience changes with the addition of particular sound mitigation treatments.
The process of mitigating noise is not a simple one. It combines a solid understanding of human factors with a strong knowledge of materials and the physics of sound. But for tenants it can make the difference between a productive workspace and a distracting one. For building owners, it means occupants that stay for the long term versus those who leave at the first opportunity. No matter how great your building looks, it is the way that it sounds that might make a difference between happy tenants and distracted ones.