Hypersonic Sound (HSS) allows sound to be directed in a narrow beam over long distances without attenuation by manipulating inaudible ultrasound. It uses frequencies over 60,000Hz to negate sound's natural nonlinearity, allowing the sound to travel focused without weakening. When the HSS hits a nonlinear object like the ear or a wall, the sound resonates and can be heard. HSS produces difference tones, where two slightly different frequencies are perceived as fluctuations in volume. Practical uses of HSS include advertising displays, military applications, performance halls, and computer speakers.
