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Re: [Phys-L] non-linear ears.

That's amazing hearing range for a human.

The web site offers "Mosquito Ring
Tones." The theory is that the higher pitches can't be heard by your
teachers. Kids can set their phones to ring at these frequencies and get
away with receiving notifications in class because their teachers cannot
hear them.

What's interesting is that the standard hearing test you might get from a
doctor only goes up to 8 kHz. They apparently don't consider hearing loss
above those frequencies to be important.


On Fri, Oct 9, 2020 at 10:28 AM bernard cleyet <> wrote:

Sorry, the brand name of an English public address system. It’s like to
hover, instead of vacuum clean.

In this case not so “public”.

bc wonders why it’s vacuum clean instead of suction clean, and suck using
a straw instead of vacuum up a drink.

On 2020/Oct/09, at 06:45, Brian Whatcott <> wrote:

This note suggests that in the usual way, an audio modulated ultrasonic
acoustic wave is inaudible to the ear, but audible to the usual microphone,
such as yours.

No, the voice was quite audible, I wasn’t deaf then. The “beam” was only
about a foot wide at a coupala yards away, i.e. ~ 0.1 radian. (6 deg.)

Brian W
Secret Ultrasonic Commands Can Control Your Smartphone, Say Researchers

| |
Secret Ultrasonic Commands Can Control Your Smartphone, Say Researchers

Voice-controlled digital assistants are increasingly common and
sophisticated. Google, Apple, Amazon, numerous c...



On Friday, October 9, 2020, 01:35:59 AM CDT, bernard cleyet <> wrote:

A friend reminded me of a demo. at the Naval Postgrad. School, wherein
an ultrasonic speaker generated wave is voice modulated in order to produce
a rather narrow bean Tannoy. I presume it works by the ear’s being
non-linear in amplitude response. Any idea if it would work W/a hearing
aid that has no gain above about 8k Hz?

bc whose hearing is about 60 dB down.

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