Sounds like an air nozzle. I get the logic behind this but unfortunately there are already industrial things that <i>make</i> that noise and they're not dangerous in the slightest unless you actually manage to puncture yourself and inject the air into your bloodstream.<br><br>Probably the best solution would be to have the white noise <i>and</i> a few quieter but discordant pure tones at once. Even if they're too low for you to pick out on their <i>own</i> they will be quite distinctive when synched up with the audible white noise pulses.