If you've ever seen a Jewish man with strings hanging out of his clothing, this is probably what you were seeing. There is no particular religious significance to the tallit (shawl) itself, other than the fact that it holds the tzitzit (fringes) on its corners.
Sound pressure or acoustic pressure is the local pressure deviation from the ambient (average, or equilibrium) atmospheric pressure, caused by a sound wave. In air, sound pressure can be measured using a microphone, and in water with a hydrophone. The SI unit of sound pressure is the pascal (Pa).
Ultrasonic Leak Detectors are most sensitive to sounds around 40 kHz, that's twice the frequency of the best human hearing. Any turbulent gas will generate ultrasound when it leaks, therefore it does not matter what gas you are leak testing.