Sound Illusions

[Jack421]

How would you account for soundwithout visible eminence such as people talking other then a form of insanityor schizophrenia? I mean as far as asound illusion. I speak of voices and sound effects seeming tocome from nowhere that are emanated as if by complicated mobile sound equipmentfrom unseen location.

 

I want to know possible ways this can be achievedto pull a prank on someone like something out of Scooby-Doo.

[Moontanman]

How would you account for soundwithout visible eminence such as people talking other then a form of insanityor schizophrenia? I mean as far as asound illusion. I speak of voices and sound effects seeming tocome from nowhere that are emanated as if by complicated mobile sound equipmentfrom unseen location.

 

I want to know possible ways this can be achievedto pull a prank on someone like something out of Scooby-Doo.

 

 

The main thing you need is an extremely gullible or naive person. I can't imagine hearing a voice like that and being fooled to think it is not a speaker nearby....

 

Having said that it is possible to project sonic illusions. They can be quite impressive in certain locations but the system to do so would have to both concealed and focused on a small area the person was in.

 

I have a stereo that I can use to make it sound very much like you are standing hear a passing freight train, at the right decibel level it is very convincing, even the floor seems to shake, but you have to keep your eyes closed or the illusion is ruined...

[Phi for All]

How would you account for soundwithout visible eminence such as people talking other then a form of insanityor schizophrenia? I mean as far as asound illusion. I speak of voices and sound effects seeming tocome from nowhere that are emanated as if by complicated mobile sound equipmentfrom unseen location.

 

I want to know possible ways this can be achievedto pull a prank on someone like something out of Scooby-Doo.

To make this prank a true illusion, you need to put your sound source in something nobody associates with making sound, like a book or a pot with a plant in it. A short range transmitter (think walkie-talkie) could be concealed in an object like that, and when the sound comes out it won't be suspected right away. Radio static could be a problem with the walkie-talkie idea, and it would be ideal if you could simply work with a one-way wireless transmitter to a receiver with as big a speaker as you can easily conceal. If it sounds tinny and scratchy, it's obviously a speaker and the illusion won't hold.

 

Cloth is good for covering a speaker without muffling the sound. Having two or more sources for the sound will prevent the mark from zeroing in on what's making the noise/voices. If you take a thick hard-cover book from a used book store, you can carefully cut out a compartment in the pages and the front cover, then recover the book with cloth, making sure to dress up the cover to look legitimate. A small silk flower arrangement can be placed in a plastic pot you've cut your speaker hole in, and the speaker goes where the dirt would normally go with real flowers. Again, cloth or a woven wicker place-mat can be used to cover the plastic pot without impeding the speaker sound much.

[Moontanman]

To make this prank a true illusion, you need to put your sound source in something nobody associates with making sound, like a book or a pot with a plant in it. A short range transmitter (think walkie-talkie) could be concealed in an object like that, and when the sound comes out it won't be suspected right away. Radio static could be a problem with the walkie-talkie idea, and it would be ideal if you could simply work with a one-way wireless transmitter to a receiver with as big a speaker as you can easily conceal. If it sounds tinny and scratchy, it's obviously a speaker and the illusion won't hold.

 

Cloth is good for covering a speaker without muffling the sound. Having two or more sources for the sound will prevent the mark from zeroing in on what's making the noise/voices. If you take a thick hard-cover book from a used book store, you can carefully cut out a compartment in the pages and the front cover, then recover the book with cloth, making sure to dress up the cover to look legitimate. A small silk flower arrangement can be placed in a plastic pot you've cut your speaker hole in, and the speaker goes where the dirt would normally go with real flowers. Again, cloth or a woven wicker place-mat can be used to cover the plastic pot without impeding the speaker sound much.

 

 

hmmm, sounds like you might have done this before...

[Phi for All]

hmmm, sounds like you might have done this before...

* remaining silent by right *

[PaulS1950]

If the space is very quiet you can produce noise with a fan that the brain will try to make sense of and it sounds like a group of people talking very low. You can't actually pick out individual words but it can be quite real. The mind tries to make sense of just about all inputs. That is why we see "animals" in cloud formations, "monsters" in the dark, flashes when we close our eyes. Try to take advantage of that and your job will be easier.

 

Paul

[ewmon]

Whispering galleries operate in a similar manner, and I personally experienced the one at the US capitol. I suppose electronics could produce something similar without the special architecture.

[Enthalpy]

A different method was investigated maybe two decades ago, where the impulse response of the room between a loudspeaker and the person's ears was precisely measured and a "decorrelation" function optimized by a Calman filter (=the known method to implement an autoadaptive filter). Then, this "deconvolution" sequence gives a pulse near the desired location but little elsewhere, as the room's response differs there.

 

Of course, it needs the subject to be immobile, since his position influences badly the room's response, and the response where the subject is.

 

I feel easier to create the sound where desired by optical means.