The correct ultrasound signal, Pompei suggests, can produce any kind of audible sound.
A novel audio beam loudspeaker which based on nonlinear propagation effects of ultrasonic in the air to generate audible sound with high directivity is presented.
A device that converts electric signals, as from a telephone, stereo, or radio receiver, to audible sound and fits over or in the ear.
Specially designed software then coded all audible sounds made or heard when the TV was both on and off.
