Ultrasonic whispers – The Hindu BusinessLine

A group of Chinese-American scientists at the University of Pennsylvania has figured out a way to deliver audio (music, podcasts and so on) right into your ear, without you having to wear earbuds or headphones, even as those around you cannot hear any of it.

The challenge of delivering audible content to a targeted listener has flummoxed sound engineers but a breakthrough, which still requires some fine-tuning, has been achieved.

Suppose you want to listen to a podcast. The audio file is stored in the car’s stereo system. The stereo system converts the podcast’s regular audio waves into ultrasonic signals — these signals are inaudible because they’re too high-pitched for human ears. However, the ultrasonic waves are so carefully aimed that they cross each other right where your head is — and they become audible sounds.

As long as your head — and ear — is in the ‘audio bubble’, you will hear the podcast. If you move your head, you will hear nothing.

The sound quality isn’t perfect yet. The scientists are working with machine learning techniques to improve the technology, according to a PNAS paper. Yun Jing, who led the research, believes that the technology has some interesting applications, ranging from home theatres to device-free communications.

Some caution that ultrasounds may harm your ear — but that’s another matter.

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Published on June 1, 2025