Architectural acoustics, the science of achieving good sound within a building, did not exist as an exact field until the late 1800s. How the curve of a wall, the shape of the ceiling, and seat cushioning influenced sound remained a mystery when buildings like the Paris Opera House, completed in 1875, were constructed. The science is now well understood, with architects and acoustic engineers knowing how to manipulate the way sound travels to provide an optimal acoustic experience.
Designing the Paris Opera House: acoustics based on chance
After winning the competition to build the Paris Opera House in 1860, Charles Garnier diligently researched how to create the best acoustics with his design. But after fifteen years of building, the architect confessed to being no further in acoustical theory than he was on day one (1).
"Nowhere did I find a positive rule of action to guide me," he said in his book, The Grand Opera in Paris (1). "I must explain that I have adopted no principle, that my plan has been based on no theory, and that I leave success or failure to chance alone" (2).
He was designing a building in a period before the field of acoustics had emerged as a science and compared the acoustician to an acrobat who closes his eyes and clings to the ropes of an ascending balloon (1).
The father of modern architectural acoustics: Wallace Clement Sabine
As architects continued to search for a theory to guide them, American physicist Wallace Clement Sabine methodically began developing the acoustics field. Now known as the father of modern architectural acoustics, in 1893, he was just a young assistant professor at Harvard University, tasked with improving the notoriously bad acoustics of the University's Fogg Lecture Hall (3).
Between 1893 and 1898, equipped with an organ pipe and stopwatch as measurement tools, Sabine studied the sound of 11 lecture halls and rooms at the University, focusing on the sound-absorbing properties of items and their impact on reverberation times (3). His goal was to develop a formula to measure and assess the acoustics of performance rooms. To do this, he spent several years comparing the poor acoustics of Fogg Lecture Hall to that of Sanders Theatre, which had excellent acoustics (3). This laborious task required repeatedly moving materials between the two spaces and making precise timings of how long it took different sound frequencies to decay to inaudibility under different conditions. Testing how the frequencies changed in the room with rugs, seat cushions, and people occupying the seats, he discovered that the average body reduced reverberation time by as much as six seat cushions (3).
Based on these experiments, he developed a formula for calculating reverberation time that shows that the sound in a room is directly related to the room's cubic volume (1). Applying his formula, he determined that the Fogg Lecture Hall's reverberation time was too long, with words remaining audible for 5.5 seconds instead of the ideal 2.25 seconds. To reduce the reverberation time, he outfitted the Fogg Lecture Hall with sound-absorbent materials (3).
The book, Acoustics of Concert Halls, explains that Sabine had learned from his tests that an audience absorbs sound in proportion to its size and that each wall, ceiling surface, carpet, and drapery-like material absorbs sound in an amount proportional to its area (1).
Sabine went on to serve as an acoustical consultant for the design of Boston's Symphony Hall, suggesting narrowed balconies to prevent the trapping of sound and materials with hard reverberant surfaces like brick, steel, and plaster. To create an optimal acoustical experience for every seat in the house, Sabine suggested the architects implement a coffered ceiling (3). To this day, the Symphony Hall is still considered to have one of the world's best acoustics (3).
Bell Telephone Laboratories creates the "bel"
With a greater understanding of how sound traveled, the vital step of determining how noise impacted the ear began.
After the creation of the telephone, Bell Telephone Laboratories needed a way to measure audio levels in telephone circuits and devised a sound measurement unit honoring Alexander Graham Bell, dubbed the "bel" (4). The bel is more commonly measured as a decibel, which is one-tenth of a bel, and helps quantify what noises can damage hearing.
A whisper measures around 30 decibels, while a normal conversation registers at 60-70 decibels. Frequent exposure to sound at or above 85 decibels, like fireworks, concerts, or factory equipment, can lead to noise-induced hearing loss (4). The ability to quantify sound on a scale helps determine what types of materials should be used in a space to either reduce or expand reverberation time.
Technological advances in acoustics
The second stage of the acoustic field spanned from 1915 to 1925 and saw a rapid expansion of knowledge. Numerous laboratories fitted with reverberation chambers measuring sound absorption and the transmission of sound through walls, floors, and ceilings were built (5).
The field of acoustics continued to become more sophisticated as the presence of technology grew. In 1962, the Precision Sound Level Meter Type 2203 was launched — the first hand-held sound level technology— an instrument used to assess noise levels by measuring the intensity of sound waves (6). The object was made by the Danish company Brüel & Kjær and had an essential role in determining if sound exposure was at a safe level for human ears (6).
The 1960s also saw the creation of the oscilloscope, making it possible to visualize and analyze sound input and reflections (7). The oscilloscope helped researchers discover more about sound direction, a helpful revelation when designing auditoriums and considering how audiences would experience the acoustics.
Modern-day “green” acoustics
As architecture evolves, a push to reduce a building's direct and indirect impact on the environment has inspired the development of green building standards, certifications, and rating systems (8). In 2000, the U.S. Green Building Council released criteria to improve buildings' environmental performance through its Leadership in Energy and Environmental Design (LEED) rating system for new construction (8).
Additionally, the Living Building Challenge (LBC), which demands 100% zero energy, net zero water, and on-site renewable energy, is "the most rigorous green building certification system in the market today." (8).
FSorb panels support the Indoor Air Quality (IAQ) credit for LEED and have the LBC product declarations. Our environmentally friendly acoustic products are made from another incredible invention, extruded polyester fiber panels that are made from a mix of recycled plastic and heat-pressed polyester, making a highly durable product that is also safe for human health, easy to work with, and affordable.
The field of acoustics has come a long way from the trial-and-error tests of investigating what objects absorb sound. There's now an abundance of information on what items work well acoustically and the best material for the different occupant needs. Acoustic design is no longer akin to a sightless acrobat depending on luck but a precise science built on discovery and research.
At FSorb, we are motivated by improving human health and do so by creating eco-friendly acoustic products. Our mission is to help designers build beautiful spaces that reduce excess ambient noise while calming the human nervous system. With over 25 years in the acoustic business we stand behind FSorb as a durable, environmentally friendly, and low-cost product. If you want an acoustic solution that is safe to human health at an affordable price, then we are your resource.
Beranek, L. (2004). Acoustics of Concert Halls. In: Concert Halls and Opera Houses. Springer, New York, NY. https://doi.org/10.1007/978-0-387-21636-2_4
If Music is the Architect. The New York Times. 2004. Retrieved January 5, 2023 from https://www.nytimes.com/2004/05/22/arts/if-music-is-the-architect.html
This Month in Physics History. APS News. 2011. Retrieved January 5, 2023 from https://www.aps.org/publications/apsnews/201101/physicshistory.cfm
Alexander Graham Bell’s Contributions to the Science of Hearing. Noisy Planet. Retrieved January 5, 2023 from https://www.noisyplanet.nidcd.nih.gov/have-you-heard/alexander-graham-bell-contributions-science-of-hearing
P. E. Sabine, "Architectural Acoustics, Its Past and Its Possibilities", The Journal of the Acoustical Society of America 11, 161-162 (1939) https://doi.org/10.1121/1.1902120
Precision Sound Level Meter:2203. Greenwood Military Aviation Museum. (n.d.). Retrieved January 5, 2023 from http://www.gmam.ca/sound-level-meter.html
Acoustics in Architecture. Physics world. 2020. Retrieved January 5, 2023 from https://physicsworld.com/a/acoustics-in-architecture/
Green Building Standards and Certification Systems. WDBG. 2022. Retrieved January 5, 2023 from https://www.wbdg.org/resources/green-building-standards-and-certification-systems