Angelo J. Campanella - a.campanella@att.net
Campanella Associates
3201 Ridgewood Drive
Columbus, OH 43026
Popular version of paper 4aAA5
Presented Thursday morning, November 18, 2004
148th ASA Meeting, San Diego, CA
In 1986, John Bradley of NRC Canada found with word score tests that speech
intelligibility in classrooms was best when background noise was below 35 dBA
and the reverberation time was less than six-tenths of a second. Not long after
that, I discovered that such conditions were also vital to classrooms for distance
learning (Ball State Telecommunications Center "Electronic Classroom"),
and for all rooms intended for teleconferencing and videoconferencing.
In 1995, design began for the Ohio State University Fisher Graduate College
of Business classrooms designed according to these precepts. For larger classrooms
of 50 to 100 students, a small flat central portion of the ceiling is made reflective
to enhance two-way unaided communication.
On completion in 1998, associate professor David Greenburg commented "..The
acoustics is awesome. Anyone can hear you if you talk in a soft voice. That's
great for faculty."
For public schools to benefit from these research findings, to fulfill our "No
Child Left Behind" efforts, economical construction methods needed to be
developed. During and after these experiences, several public schools have been
designed and
built in Ohio according to these principles.
Acoustical design is a local decision, augmented by acoustical consultants advising local architects on cost-effective acoustical design strategies. Carpets are helpful in reducing activity noises, but may not always be practical. Reverberation is economically reduced with common acoustical tile that must also provide good sound isolation between classrooms. Wall boards, bookshelves and posters provide wall sound absorption on classrooms in full use. Common central-air conditioning provides the needed quiet cool air.
We found that simple relocation of damper and fan (VAV) boxes to the corridors
outside the classroom and using flexible ducts over the classrooms achieved
the needed quiet. Manufacturers now produce quieter VAV boxes. Architects
comment that the only perceptible cost difference from previous practice is
that some duct lengths are increased. Classrooms built on these principles are
immediately accepted and placed into continuous productive use. The recently
released ANSI 12.60 standard for the acoustical design of classrooms reflects
these findings.