Sound laser built by YouTuber creates an 'invisible speaker' effect.

A YouTuber demonstrated a handheld device that sends a narrow ultrasonic beam which the air demodulates to produce audible sound only within the beam; the video explains the carrier-wave method and notes lingering questions about safety standards for high-power ultrasound.

A YouTuber on the Electron Impressions channel demonstrated a handheld device that projects a narrow beam of sound and plays music that is audible only when the beam hits the listener. The device operates at ultrasonic frequencies that are too high for humans to hear directly, and the video shows audio disappearing when the beam is moved off-target. Instead of using a radio receiver, the system uses an ultrasonic carrier wave with the music waveform superimposed for transmission. As the beam travels, air pressure changes cause the ultrasonic signal to demodulate and produce audible sound in mid-air, creating an "invisible speaker" effect. Key points: - The demonstration shows music audible only within a narrow beam aimed at the listener, as shown in the video. - The device emits ultrasonic waves (kilohertz-range) so the carrier itself is inaudible to humans. - The music is placed on the ultrasonic carrier wave and recovered as the beam travels, a process similar in principle to radio demodulation. - Air pressure variations along the beam cause the ultrasonic signal to distort and produce audible sound without a separate receiver. - The accompanying write-up notes that many health institutions have approved directional sound uses at power levels above 110 dB, but it also says there is uncertainty about whether those standards should be revisited. Summary: The device illustrates that focused ultrasonic beams can create audible audio only along a narrow path by using a carrier wave that the air demodulates, and the demonstration has prompted discussion about possible applications and safety. Undetermined at this time.