The Father of Modern Architectural Acoustics

Hello,

I wanted to jump right in and start with a little history lesson in acoustics!

Acoustics have been around for a very long time, but there was one guy in particular that most call the father of modern architectural acoustics.  His name was Wallace Clement Sabine.

In as easy and simple terms as I can make it, he figured out this idea of giving a number to reverberation and how to quantify absorption into a coefficient.

Ill start out by explaining his way of measuring reverberation in a room.  

In 1895 Sabine was at Harvard working in the physics department. The University had built the Fogg Lecture Hall not too long before, and quickly found out that the room was unusable and classified impossible to fix by senior members of the department.  When the room was partially empty, the students were not able to understand the professor. Eventually, the problem landed on Sabine's lap.

Conducting several tests using nothing more than a portable pipe organ, trained listeners, and a stopwatch, he played the pipe organ at a controlled level and stopped it immediately.  His trained listeners then told him when the sound became inaudible.  Without getting real deep into the topic, the difference was about 60 decibels (dB).  This is where the term RT60 comes from.  It was the amount of time it took sound to decay 60 dB.

Fogg Lecture Hall took approximately 5.5 seconds to decay 60 dB.  After doing the same experiment on several other lecture halls, and concert halls he came to the conclusion that a good concert hall had a reverb time (RT60) of approximately 2-2.25 seconds, and a good lecture hall had an RT60 of 1 second.

Now, on to his work on absorption.

During his many studies on the Fogg Lecture Hall, Sabine figured out that by adding seat cushions to the chairs in the room, he could reduce the RT60.  He determined that by adding 6 seat cushions to the room, it was equivalent to 1 person.

Eventually he wanted to be able to put a number to absorption.  By creating a number system, he was able to define how effective a material was at absorbing sound.  The scale developed is between 0.0-1.0 sabines.  1.0 was defined as 1 square foot of open window, meaning everything that hits that one square foot of open window is 'absorbed'.

Along with his discoveries at Fogg, he also developed several concert and lecture halls including Symphony Hall in Boston (considered by many to be one of the best sounding halls).  He also started Riverbank Labs in Geneva, Illinois.  Riverbank is a leader in providing acoustic data for product currently used by many major companies.

The life of Wallace Clement Sabine is a fascinating one and he provides much insight into the world of acoustics! I hope you enjoyed this bit of history about Sabine!

Until next time!

Tom Noble