2009 Winter Symposium: Training Classes: Floyd Toole

Loudspeakers and Rooms: Designing Listening Experiences -Floyd E. Toole

8 hours - Cost $350 (members) / $450 (non-members). Includes lunch and a copy of Dr. Toole's book “Sound Reproduction: loudspeakers and rooms”

When reproducing sound in small rooms our perceptions are governed by the loudspeakers and the listening space acting as a system.  In terms of sound quality and aspects of direction and space, the behavior of the system is different at different frequencies.  Quantifying the performance of loudspeakers and rooms requires acoustical measurements.  The challenge is to identify the relevant dimensions to measure, the necessary resolution and range of those measurements, and a manner of presentation that allows them to be interpreted in terms of listener perceptions.  It is not surprising to find that simple measurements of loudspeakers are inadequate and that, in small rooms, the sound field is such that some of the traditional acoustical measures, developed in large spaces, are not helpful. 

Reviewing the existing science, it seems that, in terms of sound quality, factors associated with the room are in control at frequencies below about 300 Hz, and the loudspeaker is the dominant factor at higher frequencies.  Naturally-occurring early reflections in small rooms are mostly benign, indeed they are helpful to speech intelligibility. However, judicious acoustical treatment of certain room surfaces can have a significant positive influence on perceptions of image broadening (ASW) and envelopment (LEV). 

The key is psychoacoustics: to know the conditions under which certain effects become audible – the thresholds – and what circumstances are required to maximize listener preferences. Only then can we define the design objectives for loudspeaker systems and the rooms within which we listen to them. When the existing scientific guidance is assembled and organized it is reassuring that much of it points to where we are. However, a few of our common practices may need “adjustment”.

Floyd E. Toole studied electrical engineering at the University of New Brunswick, and at the Imperial College of Science and Technology, University of London, where he received a Ph.D.  In 1965 he joined the National Research Council of Canada, where he reached the position of Senior Research Officer in the Acoustics and Signal Processing Group.  In 1991, he joined Harman International Industries, Inc. as Corporate Vice President – Acoustical Engineering.  In this position he worked with all Harman International companies, and directed the Harman Research and Development Group, a central resource for technology development and subjective measurements, retiring in 2007.
          

Dr. Toole’s research has focused on the acoustics and psychoacoustics of sound reproduction in small rooms, directed to improving engineering measurements, objectives for loudspeaker design and evaluation, and techniques for reducing variability at the loudspeaker / room / listener interface.  For papers on these subjects he has received two AES Publications Awards and the AES Silver Medal.  He is a Fellow and Past President of the AES and a Fellow of the Acoustical Society of America. He has just completed a book “Sound Reproduction: loudspeakers and rooms” (Focal Press, due August 2008).

Back to training classes main page