If you amplitude modulated a 40Khz ultrasonic sound that you could obviously
not hear with audio, could you hear it?
I was thinking it might be a good way to beam audio.
Brian

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In article , Brian Gaff
wrote:
If you amplitude modulated a 40Khz ultrasonic sound that you could
obviously not hear with audio, could you hear it? I was thinking it
might be a good way to beam audio. Brian

Yes, people have indeed reported modulation high power level ultrasound to
'project' audible sounds. Works by being so loud as to function via
nonlinearity. So best avoided! Bad for the ears and for quality.

Jim

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Brian Gaff wrote:

-------------------

If you amplitude modulated a 40Khz ultrasonic sound that you could obviously
not hear with audio, could you hear it?


** Yes, but with many conditions and limitations. It's a fringe idea looking for an application that others methods cannot do better.


I was thinking it might be a good way to beam audio.

** Really ?

A very effective way to "beam audio" is to frequency modulate pulsed, Infra-Red light from an array of LEDs. Perfectly possible cover an entire hall or auditorium this way, or use a much narrower beam if desired.

Listeners wear lightweight, battery powered headphones fitted with a sensitive IR detector, FM demodulator and audio amplifier. Sennheiser made and still make systems like this intended for "assisted hearing" or language translation for audience members.

I once got a box of about 30 IR headsets plus master transmitters dropped on me from a local Theatre & Performing Arts centre for their 5 yearly service and battery change. NiCd button cells have a limited life when left on continuous charge and most showed signs of corrosion too.

The carrier frequency used in the late 1980s was about 40kHz ( so ultrasonic ?) and audio modulation was extracted by a common IC found in FM tuners. Sound quality was good with only a slight background hiss.

The "line of sight" only nature of IR audio systems is actually a big plus in such environments.



..... Phil

Phil Allison wrote:

Listeners wear lightweight, battery powered headphones fitted with a
sensitive IR detector, FM demodulator and audio amplifier. Sennheiser
made and still make systems like this intended for "assisted hearing" or
language translation for audience members.

Probably quite annoying if the audience is watching a 3D film using LCD
shutter glasses though ...

Andy Burns a smug prick who thinks he is smarter than everyone wrote:

--------------------------------------------------------------------


Listeners wear lightweight, battery powered headphones fitted with a
sensitive IR detector, FM demodulator and audio amplifier. Sennheiser
made and still make systems like this intended for "assisted hearing" or
language translation for audience members.

Probably quite annoying if the audience is watching a 3D film using LCD
shutter glasses though ...


** Who said IR phones were useful in cinemas ?

My post specifically mentioned halls, auditoriums and live theatre productions - where they cater mainly older members of the audience who may find themselves seated near the back and unable to follow dialogue.



..... Phil

Oh I know about those as they are used for audio description in cinemas and
theatres. I was thinking more of exhibitions where an exhibit has a button
to press to hear a description, but if there are a lot of these the sound
when used normally is spilling over to other exhibits and hence makes it
hard to detect the one you want.
However if it has to be so loud as to make ears go into clipping even
though you cannot hear the actual frequency then its a non starter.
Brian

--
----- -
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please!
"Phil Allison" wrote in message
...
Brian Gaff wrote:

-------------------

If you amplitude modulated a 40Khz ultrasonic sound that you could
obviously
not hear with audio, could you hear it?


** Yes, but with many conditions and limitations. It's a fringe idea looking
for an application that others methods cannot do better.


I was thinking it might be a good way to beam audio.

** Really ?

A very effective way to "beam audio" is to frequency modulate pulsed,
Infra-Red light from an array of LEDs. Perfectly possible cover an entire
hall or auditorium this way, or use a much narrower beam if desired.

Listeners wear lightweight, battery powered headphones fitted with a
sensitive IR detector, FM demodulator and audio amplifier. Sennheiser made
and still make systems like this intended for "assisted hearing" or language
translation for audience members.

I once got a box of about 30 IR headsets plus master transmitters dropped on
me from a local Theatre & Performing Arts centre for their 5 yearly service
and battery change. NiCd button cells have a limited life when left on
continuous charge and most showed signs of corrosion too.

The carrier frequency used in the late 1980s was about 40kHz ( so ultrasonic
?) and audio modulation was extracted by a common IC found in FM tuners.
Sound quality was good with only a slight background hiss.

The "line of sight" only nature of IR audio systems is actually a big plus
in such environments.



..... Phil

The whole point of my idea was that no equipment is needed by the user. its
well known that these devices need to be recharged and ones in cinemas are
often not working etc, so from my point of view, if you could beam it to the
person then it might be easier. Brian

--
----- -
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please!
"Phil Allison" wrote in message
...
Andy Burns a smug prick who thinks he is smarter than everyone wrote:

--------------------------------------------------------------------


Listeners wear lightweight, battery powered headphones fitted with a
sensitive IR detector, FM demodulator and audio amplifier. Sennheiser
made and still make systems like this intended for "assisted hearing"
or
language translation for audience members.

Probably quite annoying if the audience is watching a 3D film using LCD
shutter glasses though ...


** Who said IR phones were useful in cinemas ?

My post specifically mentioned halls, auditoriums and live theatre
productions - where they cater mainly older members of the audience who
may find themselves seated near the back and unable to follow dialogue.



.... Phil

Brian Gaff wrote:

-----------------

The whole point of my idea
was that no equipment is needed by the user.


** Your idea ???


So the user has no control the sound nor can turn it off.

Damn silly idea if you ask me.



its
well known that these devices need to be recharged and ones in cinemas are
often not working etc,


** Then ask for one that works.


so from my point of view, if you could beam it to the
person then it might be easier. Brian


** You really do have some wacky expectations.



...... Phil

Brian Gaff wrote:

----------------------

Oh I know about those as they are used for audio description in cinemas and
theatres. I was thinking more of exhibitions where an exhibit has a button
to press to hear a description, but if there are a lot of these the sound
when used normally is spilling over to other exhibits and hence makes it
hard to detect the one you want.



** IR headphones can do that job, just define the IR energy to a marked area near the exhibit and illuminate from above.


...... Phil

Brian Gaff wrote:

-------------------

If you amplitude modulated a 40Khz ultrasonic sound that you could obviously
not hear with audio, could you hear it?


** Yes, but with many conditions and limitations. It's a fringe idea looking for an application that others methods cannot do better.


I was thinking it might be a good way to beam audio.

** Really ?

A very effective way to "beam audio" is to frequency modulate pulsed, Infra-Red light from an array of LEDs. Perfectly possible cover an entire hall or auditorium this way, or use a much narrower beam if desired.

Listeners wear lightweight, battery powered headphones fitted with a sensitive IR detector, FM demodulator and audio amplifier. Sennheiser made and still make systems like this intended for "assisted hearing" or language translation for audience members.

I once got a box of about 30 IR headsets plus master transmitters dropped on me from a local Theatre & Performing Arts centre for their 5 yearly service and battery change. NiCd button cells have a limited life when left on continuous charge and most showed signs of corrosion too.

The carrier frequency used in the late 1980s was about 40kHz ( so ultrasonic ?) and audio modulation was extracted by a common IC found in FM tuners. Sound quality was good with only a slight background hiss.

The "line of sight" only nature of IR audio systems is actually a big plus in such environments.



.... Phil


Well there's got to be something better than the baseband inductive
loops that are the standard in the UK.
--

Graham.
%Profound_observation%