By combining ultrasound with a concept called nonlinear acoustics, you can create sound that stays silent until it reaches a ...

Controlling where sound goes is difficult because of a phenomenon called diffraction – the tendency of sound waves to spread ... audio in public spaces. For example, museums could provide ...

The wavelength is unchanged after diffraction. A gap width similar to the wavelength of the waves passing through causes a lot of spreading, eg sound waves passing through a doorway. The greater ...