Abstract: Devices, using emitted acoustic signals and received vibrations, determine resonant frequencies of a surface or other object, and determine useful information about that surface, including size, thickness, and material. Received vibrations include impulse vibrations from striking that surface with a finger or stylus, or from a frequency or from a swept-sinusoid emitted by the device. The device can adjust its frequency output to use the surface as an amplifier for alarms or speakers, or a center frequency for sonic output. Using an accelerometer, devices sense impulse vibrations, translating those impulses into information, such as keystrokes, game controls, mice, or musical instrument controls. Devices can emulate keyboards and input devices using tabletops. Devices can coordinate signals through multiple media, including air, surface, or EMF channels.

Abstract: Devices, using emitted acoustic signals and received vibrations, determine resonant frequencies of a surface or other object, and determine useful information about that surface, including size, thickness, and material. Received vibrations include impulse vibrations from striking that surface with a finger or stylus, or from a frequency or from a swept-sinusoid emitted by the device. The device can adjust its frequency output to use the surface as an amplifier for alarms or speakers, or a center frequency for sonic output. Using an accelerometer, devices sense impulse vibrations, translating those impulses into information, such as keystrokes, game controls, mice, or musical instrument controls. Devices can emulate keyboards and input devices using tabletops. Devices can coordinate signals through multiple media, including air, surface, or EMF channels.