I spent most of my October outdoors (doing laneway house acoustic tests across Vancouver’s residential neighborhoods), enjoying the gorgeous tree-lined autumn streets and mesmerized by leaves that sparkled under the cheerful October sun. Now that rainy, grey November has settled in, I am reminded of my first year acoustical tests in the reverberation chamber.
A particularly sunny and beautiful autumn in Vancouver this year
Many acoustical standardized testing procedures require a reverberation chamber as standard facility. A reverberation chamber is the opposite of the anechoic chamber (see post on field trip and lab sessions out at UBC). While UBC has the anechoic chamber, BCIT has the reverberation chamber, located just behind the CARI building on Mathissi Place, just west of the Burnaby campus across Willingdon Avenue.
The reverberation chamber/sound transmission lab, image from BCIT Commons.
The reverberation chamber minimizes sound absorption and maximizes sound-reflections, thus keeping the sound energy level high in a room. This acoustical phenomenon is called “reverberation” and exists in all built rooms. For any room there is a “reverberation time” and this is used as the acoustical signature or fingerprint of the room.
The reverberation chamber generally has a very long reverberation time (because sound keeps reflecting or bouncing around in it and is slow to dissipate). The chamber generally follows a specific size range and interior surface specifications in order to comply to standard requirements for testing.
Our reverberant chamber was originally constructed in 2008 under the direction of Dr. Connelly for research work on green roof sound transmission. The roof of the standalone chamber can be hoisted off and replaced with different green roof samples. The interior wall surfaces are all concrete and highly reflective to sound; thus, whatever you say in side becomes louder and less clear due to echoing and reverberant effects of the room.
Last year, I did an acoustics course project measuring sound absorption characteristics of green roofs. The ASTM standard I followed requires use of the reverberant chamber to measure specimen sound absorption. So, I spent many long days at the dark and lonely chamber doing room reverberation tests (which required a high level of fastidiousness… arg!). The tests continued from November through April and took up many weekends and spring break days.