In our everyday lives, we’re surrounded by sound – whether it be a bustling city street, peaceful noises of nature, or music playing in the distance at a crowded concert. The environment, whether it be a large auditorium or a small classroom, plays a huge role in how we experience those sounds. This opens up opportunities to control and manipulate our acoustic experience simply by adjusting properties of the physical spaces.
In 99% Invisible’s “Reverb: The Evolution of Architectural Acoustics,” Roman Mars breaks down this science of auditory architecture and acoustic control. “Today, through a combination of passive and active acoustics, architects and acousticians can control the sounds of spaces to fit any kind of need,” explains Mars, host of the podcast. “With sound-proofing and selective-amplification, we can add reverb or take it away. We can make churches sound like clubs and clubs sound like opera houses.”
Think passive and active acoustics
In any given space, there are two basic way architects can control the way sound waves move: active and passive acoustics. Active acoustics involve the actual technology and systems used to produce sounds, such as speakers, while passive acoustics make up the composition and the layout of a given space.
Both are used in modern architectural acoustics -- the design of buildings incorporating how sound will be received and transmitted. This design thinking began in 1895 when Wallace Sabine, a Harvard physics lecturer, was tasked with improving the Fogg Art Museum, which had a hall so reverberant that it was hard for people to follow the lectures.
Through his studies, he developed the equation that would later take his name: the Sabine Equation. By calculating a space’s acoustic quality, size, and amount of reflective versus absorbing surfaces, Sabine was able to estimate the reverberation of a given room, and thus help control the sound quality.
One of the first examples of a successful use of architectural acoustics was in the St. Thomas Church, located in New York City. Sabine collaborated with tile manufacturers to produce acoustical tiles, which used a porous surface to absorb sound. These tiles were used in the church to muffle reverb, all while preserving the Gothic aesthetic of the building.
With his breakthrough at St. Thomas Church, architectural acoustics grew. All sorts of environments invested in muffling reverb and soundproofing in order to satisfy the growing demand for silent spaces. Throughout the early 20th century, buildings and rooms slowly improved methods of keeping sound out, and quiet in.
Reverb went out of style and came back
In the 1970s, the public eventually saw a return in the need for reverb. The ability to control and change acoustic spaces became the new way to design and build architecture. Currently, the focus of acoustic architecture lies more in the control of sounds and less in the repression of reverb. Modern architects use both passive and active auditory control in order to design buildings with customizable acoustics. This allows for rooms of any shape and size to accommodate myriad establishments, such as clubs, churches, or restaurants. Volume and reverb can all be controlled via technology, so no matter the situation, the sound can be managed.
In particular, the use of active acoustics have advanced to give maximum acoustic regulation via digital manipulation. Small speakers and microphones can be used to adjust reverberation, which in turn can give the illusion of the space having different dimensions. Such technology allows for users to have absolute control over how their room sounds, whether it be to people in the room or outside listeners.
Through numerous improvements to both our understanding of architectural acoustics and the equipment used to manipulate sound, our auditory control has reached new heights. Due to Sabine’s research and its implementation in buildings, reverberation, and volume can be easily handled by technology. This allows any room to accommodate to a user’s preference, and furthers our enjoyment and usage of a variety of spaces.
If you find how architects control the reverb of a room interesting, we highly recommend checking out this video of an anechoic chamber.