Ultra-sound counter-measures work like most other ECCMs against electro-magnetic sensors as well: You either remain unseen from the waves, by not offering a cross section from which they can bounce back (aka "stealth") or you flood the em-spectrum with noise; the latter meaning you need to know the approximate frequency and then transmit more powerful ultra-sound emissions on it than the sensor you want to blind.
Finding out the exact frequency sounds difficult, but alas commonality in industry standards, including "set wavelength" for civilian and military usage will basically reduce the frequency band two a certain set of frequency bands that would be well known by every technician and EC(C)M expert. If you want to blind a specific sensor and not just the complete frequency band, you might also try a directional jammer, but you would need to find a way to keep it tracking the targeted sensor. In a world of wifi-hooked devices that shouldn't be a problem, but if your player goes offline, you would need traditional triangulation-devices. Those might not be at hand, since ultra-sound is less frequently used in the military (except for naval sonar), because of it's short range in the atmosphere.
But basically all you need to have for that is three or more ultra-sound detectors on gimbles and a program that turns the gimbles towards the "loudest" (or otherwise predetermined) source and then calculates (triangulates) the position of the source depending on the diffrence between the time the sound waves need to travel to the sensors. Of course you need to know the exact position of the sensors. So if the sensors move, they should have GPS and feed that data to the program as well. The rest ist mathematics and a matter of your computer's calculation speed. So in SR this should be near-instant-