[Racer26]

Yup, perfectly normal. I expect this is an artifact of 150Hz being well within human hearing range of 20Hz-~20kHz. The 15kHz of the Jags is much higher up the spectrum, and thus many people can't perceive sounds of that frequency (hearing range decreases with age).

Compare this to the high-pitched screech emitted by many older CRT televisions. Children and teens can hear an energized TV like that from rooms away, while adults can't hear it at all.