PSCU 2019: A Brief Introduction to Architectural Acoustics
According to the Centers for Disease Control and Prevention (CDC) National Health Survey in 2014, hearing loss is the third most common chronic physical condition following arthritis and hypertension. Hearing loss is twice as prevalent as diabetes and cancer.
During her PSC University 2019 presentation “A Brief Introduction to Architectural Acoustics,” Alanna Watts, PE, said, “We are all familiar with extensive requirements for ambulatory disabilities, but do you guys know of any requirements for hearing impairment in the ADA Accessibility Guidelines?” She went on to say that requiring architects and designers to comply with standards for acoustics would help people who have already experienced hearing loss as well as those who have not. Measuring sound, absorption materials, analyzing the critical path for mechanical systems in buildings and sound transmission through buildings are all objectives that can improve the acoustics of a space’s design.
There are several factors that affect acoustics relating to design of the space and as well as varying occupancy of a space. Reverberation time, air absorption, sound pressure levels, background sound, fans and air ducts are a few examples. Using laws of physics, equations, design principals and specialized equipment such as sound level meters, Alanna said solutions can be found to improve the acoustics of a space.
The Meyer Sound Constellation System is one example of a flexible acoustical design that has proven to work. If an owner wants a noisy bar area next to a quiet seating area, this can comfortably be achieved with this system. Bellota, a San Francisco Bay restaurant in California, has a series of microphones, loudspeakers, and subwoofers installed – all adjustable to improve the acoustics depending on the occupancy in the space.
In addition to the amount of people, noise of staff and background music, design of the building and systems within the building can contribute to the ability or inability to hear well in the space. Humming from air ducts is a sound energy known as breakout noise. Duct silencers are a tool that can be installed to filter out that noise from HVAC systems.
Static silencers are either dissipative or reactive. Dissipative silencers have sound-absorbing materials such as fiberglass that are usually encased in perforated liners. Reactive silencers reduce sound using the Helmholtz resonator principle. Dynamic, or active, silencers electronically generate a sound wave that is equal in amplitude but opposite in phase to cancel out a sound’s source. Most silencers used in common HVAC systems are dissipative.
There are many other tools and design principles that can be used to improve the acoustics of a space. Creating regular practices through standardized requirements will help designers to master the complexities of acoustics and benefit those who are as well as those who are not affected by hearing loss.