Sound Design in Higher Education and Workspaces: The Basics of Acoustics for Architects

By Ashleigh Snider, Design Intern

Point of View

Ashleigh Snider joined the Bozeman studio as a summer design intern, participating in the firm’s robust internship program that includes conducting an in-depth research project. Ashleigh graduated with a Bachelor of Arts in Architectural Environmental Design from Montana State University in May 2024. Read more from our 2024 internship cohort and all our past intern research projects here.

 

Introduction to Acoustics

Acoustics of a space directly affect our experiences in a certain environment; as such, it is crucial to consider a holistic design approach. Poor acoustics impairs communication, which can lead to a reduction in concentration and safety. Acoustics also affect our health and well-being: poor acoustics such as excessive noise levels and disruptive sounds can cause stress and result in poor sleep. Acoustics are also crucial to enhancing the performance quality of a space and the overall enjoyment of music. However, acoustic treatments are often the first thing to be taken out of a project to reduce building costs, and there is only one mandatory code for acoustic standards — even though acoustics are incredibly important for the functionality of a building.

The Basics

Understanding the basics of how sound works in a space is crucial to understanding the effective design solutions for improving acoustics in the built environment. Sound is measured in decibels, which uses a logarithmic scale, meaning that it is proportional to its intensity, not its loudness. For example, a change in 10 dB, going from 40 dB to 50dB, is perceived as getting twice as loud. Sound measured between 0 – 30 dB is considered very soft, 31 – 60 dB as quiet, 61 – 80 dB as annoying, and decibels measuring 81+ can be potentially harmful, especially if exposed to it for a long duration of time.

Background noise is the accumulation of all the noises present in an environment, including exterior and interior noise, and is controlled by limiting the transmission of such noises. Exterior noise can be through the urban environment such as traffic, or natural noises like wind and rain. Interior noises can be airborne (student-generated noise, light fixtures, sound flanking through open gaps in walls and other assemblies) or structural, where the sound vibrates through the structure and assemblies and gets transmitted into spaces beyond it. Background noise is incredibly important to control as it affects the speech intelligibility of a space, as well as the comfort of building occupants.

Reverberation time is the time it takes 60 dB to fully decay in a space. Because it is a measure of how sound persists in the space, it is used to determine many things such as speech intelligibility and the quality of sound/music. Typically, lower reverberation times are wanted for space like classrooms and speech-dominated activities because the persistence of sound can begin to make speech sound muddy and difficult to understand clearly. On the other hand, having higher reverberation time allows music to sound fuller and richer as the sound envelopes the space.

The following graphic is a visual analogy of how both background noise and the reverberation times affect speech intelligibility.

The ABCs

Absorb: Utilizing absorptive ceiling and wall panels can reduce reverberation times, as less sound is now being reflected off the rooms’ surfaces. Ceilings are the most effective because most of the time, walls are used for daylighting and other functions of a space. A material’s absorptiveness is measured by its noise-reduction coefficient, a number between 0 and 1 (0 meaning no sound is absorbed, and 1 being fully absorptive).

https://www.secondskinaudio.com/acoustics/what-is-nrc-rating/

Block: Blocking sound first begins with thoughtful programming of space. By doing an acoustic analysis of the site and what activity is the main purpose of each space in a project, you can be strategic with the placement of rooms and spaces to help with acoustics. For example, placing rooms that share the use of quiet activities adjacent to each, instead of one loud room next to a quiet room, allows for thinner wall build up (because adding mass to an assembly improves its acoustical qualities) and ends up saving money and materials.

Cover: Cover consists of using a strategy like sound masking, which uses additional sound to cover or even-out existing sounds within a space, which can increase occupant comfort and privacy. This can be done through artificial noise through sound systems built into buildings, or through more natural features like water fountains.

Internship Experience

This summer has been so enjoyable, and I am truly grateful to Hennebery Eddy for giving me the opportunity to learn all the profession has to offer. I was able to learn how a project goes from schematic design phase into the construction drawings and be a part of that process and was able to learn so many new skills in Photoshop, Revit, and more. I am so excited to continue to learn and apply all this knowledge as I head into my first year of my master’s degree at Montana State University.

Research Sources