Ultrasonic animal deterrents are legally sold in many countries, including ones designed to deter human animals (the teenager-annoying ones). So yes, noise is a problem and that's how some people want it.

It's likely that your soundbar has a high frequency switching power supply, and entirely possible that it is emitting sound above your hearing (the upper limit decreases with age and can be under 10kHz). One cheap option is a frequency display app for your phone, which should go up to 20kHz or so. That won't give you "true" ultrasonic, but will cover some range that you probably can't hear, and may show harmonics of any actual ultrasound.