Figure 1 shows an untrasound spread spectrum implementation prototype which is essentially a Raspberry Pi, a low-power audio amplifier and a transducer that has good audio capability between approximately 5 kHz and 25 kHz. This is the spread-spectrum output device; the receive devices were PCs or mobile phones.
This prototype has been used to demonstrate robust information transfer in rooms aproximately 20 feet by 40 feet with output SPLs lower than 65 dB SPL - even when this prototype was put inside the speaker podium which had no direct path to the room volume.
Most speakers/transducers and microphones on consumer devices can accommodate most designs using frequencies between 5 kHz and 25 kHz (Nyquest criterion and other I/O capabilities limit descrete signal processing desings).
Michael A. Ramalho
Last Modified on : October 14, 2019
Page Owner : Michael A. Ramalho, Ph.D.