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Most microphones are designed to emulate the human ear, hearing sounds that we hear, and not hearing ones that we don't. Scientists from the University of Illinois at Urbana-Champaign, however, have created a new sound that we can't hear but that is picked up by mics of all kinds. It could have some valuable applications, although there's also the potential for misuse.
The university's Coordinated Science Laboratory states that the sound is produced by combining multiple tones that interact with a microphone's mechanical workings, creating what is known as a "shadow" – this is a type of white noise that is detectable only by the microphone, as it's formed within the mic itself.
Transmitted by ultrasonic speakers within a room, the sound could be used to keep confidential conversations from being clearly picked up by hidden listening devices. The people talking would still have no problem hearing each other, as the sound would be inaudible to them.
It could also thwart illegal audio recordings in movie theaters or music venues, plus it could be used in place of Bluetooth for wireless communication between Internet of Things (IoT) devices.
(Score: 2) by JoeMerchant on Wednesday June 28 2017, @12:27PM
In the 1970s/80s ultrasonic motion detectors for security systems were all the rage. Unfortunately, the designers apparently considered frequencies "above the perception threshold" of 99.9% of the human population to be adequately high - I could hear them, and they were painfully loud. I knew many people who could actually perceive them, though not as a painfully loud sound, but as a general discomfort vaguely associated with the ears. Funny thing about a shopping mall with 2000 shoppers in it, just by straight statistics: 99.9% doesn't include every person in the mall. If you want to go all civil rights on the thing, those systems were discriminating against people with acute high frequency hearing, denying them the opportunity for employment, and even denying them access to shop without having to wear some pretty serious hearing protection.
Same kind of problem applies to flashing screens on video games. Only 1% of the population has epilepsy, and only 1% of epileptics are "flash sensitive," that's a really small group, but it's still 1 per 10,000, and it includes somebody that a high-up in Sony management cares about, so we get those warnings before all the video games - which is probably appropriate since Sony has sold far more than 10,000 video game consoles.
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