Sam Clapp is a Ph.D. student in the Architectural Acoustics program at RPI. His research focuses on using spherical microphone arrays to study room acoustics. He earned his Bachelor’s degree from Williams College, where he double majored in Physics and Music, and worked for several years at Young Concert Artists, a non-profit organization in New York City devoted to launching the careers of young classical musicians.
One important area of interest in the Architectural Acoustics field is finding meaningful ways to compare different spaces in terms of listeners’ subjective experiences. One big obstacle to achieving this is that auditory memory is very short – in the time that it takes to travel from one space to another, listeners lose the basis for a truly rigorous aural comparison. Thus, we desire ways to realistically recreate the acoustics of different spaces in a controlled environment. This allows the listener to hear different spaces back-to-back, and allows the researcher to control for all of the other variables that affect one’s enjoyment of acoustical spaces such as mood, time of day, quality of the performance, etc.
One common method to accurately simulate different spaces is through binaural recording. Such a recording is made with a dummy head, a mannequin that contains a microphone in each ear. The physical presence of the head acts to create the appropriate timing delays and acoustic shadowing that occur when we listen to sounds in a natural environment. The signals recorded in each ear of the dummy head can later be played back directly to listeners via headphones. While this method is simple and elegant, it requires listeners to keep their heads completely still to maintain fidelity of the acoustic image, and there are many acoustic cues that we access through small head movements.
This suggests the need for a loudspeaker-based system, which would allow for head movements. The system that we have turned to is known as Ambisonics, which works by decomposing the soundfield into a set of spatial components, and then reassembling it for a listener in the center of a three-dimensional loudspeaker array. My work for the summer internship project involved investigating how well different loudspeaker arrangements might accurately reproduce sounds originating from specific directions through computer simulations. This will lay the foundation for future work involving testing the performance of real loudspeaker arrays, and synthesizing more complex sound events, with the goal of creating a reliable, high-fidelity system for creating realistic, immersive auditory simulations.