This post isn't particularly scientific or detrimental to any particular project, it's more for fun/curiosity. I had the thought that maybe there is a way to jam or confuse a robot that relies on ultrasound for navigation. I'm going to try this today and will let you know what I find out.
I've downloaded a free app on my phone that is a dog whistle. Basically it's a tone generator that lets you select from a bunch of presets or you can enter your own frequency. You can set it as high or low as you want and can even set it to pulse and select a preset pulse range. According to technical documents I've read, the HC-SR04 ultrasonic rangefinder operates at 40kHz or 40,000mHz, which this app seems to be capable of. I'm going to see if I can jam one of my robots when I get home with this app and will let you guys know.
I suppose it could be a good thing to know for the guys building sumo-bots since a lot of those rely on ultrasound to locate their targets. If the other robot is blasting a 40kHz signal constantly, it's going to throw off the measurements of the other robot.. or maybe draw attention to itself. I have let two of my robots loose in my house at the same time though and they didn't seem to be causing each other any grief but it might be that they never happened to be listening for an echo at precisely the same time.
Has anybody else tried this out?