Dog whistles and cell phones.

[Gunluvver2]

If a dog whistle is blown near a cell phone could a dog in the area of a
receiving cell phone hear the ultrasonic sound from the cell phone? I know it
is a crazy question but I read this in a mystery story I read recently. Can
ultra sound be transmitted over cell phones or regular phones and heard on the
other end or registered on instruments that detect ultrasound?
TIA
DL

 

[Jacobe Hazzard]

Gunluvver2 wrote:

If a dog whistle is blown near a cell phone could a dog
in the area of a receiving cell phone hear the ultrasonic
sound from the cell phone? I know it is a crazy question
but I read this in a mystery story I read recently. Can
ultra sound be transmitted over cell phones or regular
phones and heard on the other end or registered on
instruments that detect ultrasound?
TIA
DL

No. Wired telephone networks use narrow bandpass filtering on the signals,
the maximumj frequency they can transmit is around 5kHz I think. I imagine
cellphones are not much different, and even if they are building a phone
network to transmit inaudibly high pitched signals would just be stupid,
don't you agree? Capability to transmit higher frequencies means wider
bandwidth means more expense and complexity with no real benefits to the
cell company or customer.

So no.

 

[Gunluvver2]

No. Wired telephone networks use narrow bandpass filtering on the signals,

Thank you for the answer. I suspected that might be the case but since I know
absolutely Zilch about electronics I wasn't sure. I guess the author of that
story knew just about as much as I do. But it did make for a good story.
DL

 

[Dr. Anton Squeegee]

In article <20031209181807.15356.00000473@mb-m12.aol.com>, gunluvver2
@aol.com says...

If a dog whistle is blown near a cell phone could a dog in the area of a
receiving cell phone hear the ultrasonic sound from the cell phone? I know it
is a crazy question but I read this in a mystery story I read recently. Can
ultra sound be transmitted over cell phones or regular phones and heard on the
other end or registered on instruments that detect ultrasound?

Extremely unlikely. I would say that the author of that mystery
story didn't do their homework.

The typical telephone passband for voice, no matter if it's wired,
wireless, or two tin cans and a string, has been spec'd for decades at
300-3000Hz. Anything above that top end gets sharply attenuated.



--
Dr. Anton Squeegee, Director, Dutch Surrealist Plumbing Institute
(Known to some as Bruce Lane, KC7GR)
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http://www.bluefeathertech.com/rf.html
"Quando Omni Flunkus Moritati" (Red Green)

 

[Steve]

voice communications bandwidth is generally accepted to be 300Hz to
3.4kHz.

Dog whistles range from 5kHz to 12kHz or thereabouts. Not quite
ultrasound. Apparently some believe dogs can hear up to 65kHz!