directional sound system

[epilot]

hi friends

i know there is a post about Hypersonic sound system somewhere at this forum,

i have read a bit about these kind of system but i dont know what is the mystery of these kind of devices(the link i read had some of points about how they do work but i can not understand the way of concentrates and transmitting as a beam...?

how these kind of device are built Really?


i think sony is selling them, am i right?

 

[audioguru]

Sony doesn't sell them.
Hypersonics use an array of ultrasonic (frequencies higher than you can hear) speakers that are modulated with audio. Speakers project very high frequency sounds only in a single direction, and placing them in an array further increases their uni-directionality. When the modulated high frequency waves strike an object or your skull then sound is produced by interference patterns.

 

[akg]

about how they do work but i can not understand the way of concentrates and transmitting as a beam...?

adding to audio
as sound freq goes higher , beamwidth reduces , so high ultrasound can form a narrow beam .

 

[audioguru]

A number of speakers in a flat array focuses the sound because a little to the side, one column of speakers is closer than the others. If it is half a wavelength closer, the sound cancels.

 

[epilot]

about how they do work but i can not understand the way of concentrates and transmitting as a beam...?

adding to audio
as sound freq goes higher , beamwidth reduces , so high ultrasound can form a narrow beam .

then any high freq ultrasonic wave must have a narrow band width and would not be effluence at all directions and only at one direction, am i right? (do you have any link for ultrasonic narrow waves?)

but the problem is that an ultrasonic wave will not convert into an audio wave when it strikes on an object!

 

[audioguru]

then any high freq ultrasonic wave must have a narrow band width and would not be effluence at all directions and only at one direction, am i right?

No. The ultrasonic waves must have a narrow beamwidth so it goes only to the correct spot and is concentrated. It must also have a fairly wide bandwidth for the modulation. They developed their own transducers for very high power.

(do you have any link for ultrasonic narrow waves?)

Look in Google.

but the problem is that an ultrasonic wave will not convert into an audio wave when it strikes on an object!

They developed a special modulation for it to produce interference patterns caused by the original wave and a reflected wave. The interference patterns are heard as sound.

 

[epilot]

A number of speakers in a flat array focuses the sound because a little to the side, one column of speakers is closer than the others. If it is half a wavelength closer, the sound cancels.

sorry but i can not understand what you said!

 

[audioguru]

A number of speakers in a flat array focuses the sound because a little to the side, one column of speakers is closer than the others. If it is half a wavelength closer, the sound cancels.

sorry but i can not understand what you said!

If you are directly in front of an array of speakers, you hear all with the same phase and their loudness adds.
If you are off-center then one vertical column of speakers is closer to you, and other columns are farther. Measure the difference in distances and calculate the frequency that is a half-wavelength. That frequency will be received out-of-phase at your ears and be cancelled.

Don't you know about speakers' phase? Speakers and the air they vibrate must be moving in the same direction at the same time for sound to be loud.
Try it. Take two stereo speakers and place them facing each other with a small gap between. Play mono music. It will be loud if the speakers are in-phase. Then reverse the wires of a single speaker to make it out-of-phase. The bass and most of the sound will be gone. Don't forget to correct the wiring after this test. :lol:

 

[epilot]

then any high freq ultrasonic wave must have a narrow band width and would not be effluence at all directions and only at one direction, am i right?

No. The ultrasonic waves must have a narrow beamwidth so it goes only to the correct spot and is concentrated. It must also have a fairly wide bandwidth for the modulation. They developed their own transducers for very high power.

what a beam width means for a mechanical sound wave really?

(do you have any link for ultrasonic narrow waves?)

Look in Google.

but the problem is that an ultrasonic wave will not convert into an audio wave when it strikes on an object!

They developed a special modulation for it to produce interference patterns caused by the original wave and a reflected wave. The interference patterns are heard as sound.

what is that interference pattern too?

 

[epilot]

A number of speakers in a flat array focuses the sound because a little to the side, one column of speakers is closer than the others. If it is half a wavelength closer, the sound cancels.

sorry but i can not understand what you said!

If you are directly in front of an array of speakers, you hear all with the same phase and their loudness adds.
If you are off-center then one vertical column of speakers is closer to you, and other columns are farther. Measure the difference in distances and calculate the frequency that is a half-wavelength. That frequency will be received out-of-phase at your ears and be cancelled.

Don't you know about speakers' phase? Speakers and the air they vibrate must be moving in the same direction at the same time for sound to be loud.
Try it. Take two stereo speakers and place them facing each other with a small gap between. Play mono music. It will be loud if the speakers are in-phase. Then reverse the wires of a single speaker to make it out-of-phase. The bass and most of the sound will be gone. Don't forget to correct the wiring after this test. :lol:

please wait audioguru!
this is what i have read before and started this forum to reach to what you said at this post.

please can you let me know more details about "out of phase" you said at that case?

i know at that example the difference at the phases (direction of the airs between 2 speakers) will remove the loud but why 2 speakers can not remove ALL the sound?!

i must reread all your comments here tomorrow because now i am a bit tired, though the time here is 12:30AM and your writings about sound are sweet for me and really i dont know which one is better sleeping or a coffee :lol:

 

[audioguru]

[why 2 speakers can not remove ALL the sound?!/quote]
The cones of two speakers are not exactly the same and they are not perfect pistons for vibrating the air the same. Your hear the difference between the way they are made. Usually speakers are different from each other at higher audio frequencies so they won't be perfectly canceled and will be heard.

 

[epilot]

[why 2 speakers can not remove ALL the sound?!/quote]
The cones of two speakers are not exactly the same and they are not perfect pistons for vibrating the air the same. Your hear the difference between the way they are made. Usually speakers are different from each other at higher audio frequencies so they won't be perfectly canceled and will be heard.

so do you thing if i use from 2 piezo electric speaker(that flat coin speakers) for a mono audio and use from an opposite wiring for that 2 piezo i can remove all the sounds?

 

[audioguru]

so do you thing if i use from 2 piezo electric speaker(that flat coin speakers) for a mono audio and use from an opposite wiring for that 2 piezo i can remove all the sounds?

Piezo speakers are crap! I call them whistles because they only play their very high resonant frequency. I don't think you would find two the same.

 

[epilot]

so do you thing if i use from 2 piezo electric speaker(that flat coin speakers) for a mono audio and use from an opposite wiring for that 2 piezo i can remove all the sounds?

Piezo speakers are crap! I call them whistles because they only play their very high resonant frequency. I don't think you would find two the same.

but i like an experiment based on loud removing, then what is solution?
i want to do a test with 2 speaker or every loud generator and remove about all the loud if i could.

any other advice is useful(although i have another question from above posts but i prefer to ask it tomorrow, time is 3:35AM and my coffee is ended up :lol:

 

[audioguru]

Some cars have a noise-cancelling system to reduce noise, by playing sounds picked-up by a microphone out-of-phase with the sound.
Noise-cancelling headphones also play noise out-of-phase with the sound picked-up by a microphone.

 

[epilot]

hi

i have searched for beamwidth ultrasonic articles or tutorial but i could not find any thing in the net...

what is beamwidth really and what is its difference with wavelength :roll:

i read an article about ultrasonic but there was nothing about concentrating narrowband, perhaps it was not a complite article!

abut directional speakers, when someone sends a sound wave over a wall or object it might pass from that object , and this passing should be very much for an ultrasonic i think(because the freq increases and so wanelength decreases) am i wrong?

 

[akg]

what is beamwidth really and what is its difference with wavelength

if u light a electric torch during a misty evening. u can see a beam of light electric from the torch.the width of that light beam is the beam width , which is not same as the wavelength of the light.
ultrasound is not same as electromagnetic wave. sound waves are propagated using particle vibration. higher the freq , greater the difficulty for the particle to vibrate.so it cannot pass thru an object as light, instead it will 'drill' that object

 

[epilot]

what is beamwidth really and what is its difference with wavelength

if u light a electric torch during a misty evening. u can see a beam of light electric from the torch.the width of that light beam is the beam width , which is not same as the wavelength of the light.
ultrasound is not same as electromagnetic wave. sound waves are propagated using particle vibration. higher the freq , greater the difficulty for the particle to vibrate.so it cannot pass thru an object as light, instead it will 'drill' that object

Hi akg,

i am trying to learn more and more

with the torch example i think your mean aboy beam width is "amplitude"
of sound wave, am i right?

another question:
if we make a VERY high freq like 1MHz then what will happen?
can this freq be vibrated by air molecules?

 

[akg]

with the torch example i think your mean aboy beam width is "amplitude"
of sound wave, am i right?

no. i have got some confusion . ok do this exp:
fill a glass tumbler with pure water , and mix some drops of milk into that to make it pale white . now pass light thru it. u can see the 'beam width' .
it is not same as the amplitude of vibration of EM Wave. normaly beamwidth will increase proportionaly with distance .

another question:
if we make a VERY high freq like 1MHz then what will happen?
can this freq be vibrated by air molecules?

yes afiak . ultrasound can go beyond that freq. the air molecules shld vibrate , otherwise no sound wave.
but heavier objects (compared to air) like water , diamond wont vibrate.
so US creates 'cavitation' in water and holes in diamond (due to heating)

 

[epilot]

what this means please?

"it is impossible to generate extremely narrow beams of
audible sound without extremely large loudspeaker arrays" :roll: