I'm currently looking to create a parametric speaker that is capable of outputting extreme levels of noise (I have no issue with the audio leaking out). The current design that I have at the moment is just a simple parametric speaker that's comprised of a Bluetooth Module, 555 timer, Amplifier, Ultrasonic Transducer Array, and other misc components. I'm looking to modify this to facilitate a larger audio output, but I'm not sure how; apologies if there's an obvious answer to this. Should I simply increase the size of the array, or amplify how much power the array is receiving? (Again, apologies if there's an easy answer that I'm missing here)
I may be missing something here but your transducers will not output in the audio range (at least no at any volume). So they will not provide any "larger audio output"
Is your vision of a parametric speaker a focused speaker or imply a number of individual speakers with the same output?
Correct me if I too am missing someone, but the 40khz noise will get demodulated once it hits a surface, converting it to a frequency that is within the range of human hearing. What I am aiming to do is amplify the noise of this demodulated sound.
The only method I am aware of to demodulate something requires a nonlinear device of some sort.
So If a "very strong" 40k hz transducer can create enough sound pressure energy to vibrate a target, the target will vibrate at 40 kHz (or a reasonably close resonant frequency). Then when the transducer is no longer energized the target will stop vibrating. Neither action will create any sound pressure in the audible range. It might be possible if the target resonant frequency(s) are lower it may heard by a young child.
In fact, such a device does exist and was demonstrated in an exhibit at the Museum of Science and Technology in Chicago, IIRC. Visitors could walk past a certain spot and here "sound coming from nowhere". It exploited the tiny non-linearity of air to convert converging ultrasound waves into audio waves
But it likely took a dedicated science team to put it together, so I ask, what is your level of experience in electronics, acoustics, and physics? A novice experimenter will not get far with this.
Increasing the amplitude of the ultrasonic signal is the only way to increase the amplitude of the perceived audio, and you can not do that beyond a minimal level, without creating a critical danger to the hearing of living things in the vicinity of the ultrasound. There is the added risk that the waves can not be perceived directly, you could put your ear very close to a powerful emitter and not know that you have destroyed your hearing for a lifetime, until a few minutes later...
Please abandon this dangerous project unless you are qualified to assess and mitigate the extreme and unpredictable risks.
I think the OP got the idea from the video linked below (which misrepresents the physics), describing Soundlazer, a product from a company that seems to have faded from view.
A few years back a similar demonstration was done in a super market to advertise to customers standing right in front of a certain product. Only that person could hear the audio. All has since disappeared.
I wonder if the phenomena was due to "beat" frequencies, or specifically a difference in two ultrasonic soundwaves in the audio frequency range? This could increase and destruct soundwaves in the audio frequency. Kind of like a mixer in a radio.
Not that video, but similar ones detailing how'd you build such a device. I wanted to adapt their circuit to be able to emit a more powerful noise upon demodulation. Here's one of the videos I watched and took inspiration on: DIY Ultrasonic Audio Laser (Directional Speaker) - YouTube
I'm of course not going to be testing nor using the device in the same way as the video I linked. I was intending to use it as a kind of deterrent for small game from a distance. Essentially just blasting their ears with a burst of noise (The level of audio of course correlating to the sensitivity of their ears, I don't want to outright deafen them)
