College - Author 1

College of Engineering

Department - Author 1

Electrical Engineering Department

Degree Name - Author 1

BS in Electrical Engineering



Primary Advisor

Dean Arakaki, College of Engineering, Electrical Engineering Department


Museum displays with audio explanations typically use headphones. A speaker’s sound at one display interferes with patrons at other displays, thus museums use headphones. These devices are either integrated into the display itself, or attached to an mp3 player. When integrated into the display, headphones can be unsanitary; when attached to an mp3 player, these devices are inconvenient. If speakers can direct sound toward an intended area, headphones can be eliminated. Acoustic horns direct sound toward a specific point, but require a large spatial footprint. Acoustic spherical concave lenses also direct sound toward a point, but exhibit excessive acoustic attenuation. Current speakers on the market that focus sound toward a location are costly compared to headphones. An acoustic gradient index of refraction lens, GRIN lens, accomplishes sound wave focusing while minimizing attenuation and decreasing material costs compared to current directive speakers. The goal of this project is to design and optimize a GRIN lens using numerical simulations in COMSOL Multiphysics and scripts developed in MATLAB. This GRIN lens must direct sound for museum exhibits; therefore, must operate in the human speech frequency band (300Hz - 3400Hz). An acoustic test chamber was designed and built in order to test and validate the physical prototype. The prototype was fabricated using PETG on the MakerGearM2 3D printer. This chamber is 1m length x 1m height x 1m depth and characterizes acoustic radiation pattern vs. azimuth angle (300Hz - 3400Hz) and the frequency response - microphone directly in front of speaker (300Hz - 10kHz) - for 3” maximum diameter speakers.