I usually listen to subliminals with earphones. I don’t have the environment to play them on speakers, or else I would have to expose the subliminals to infants, and other people. I am aware of the volume caution of ultrasonic in the case of earphones.
For example: 1 loop of masked (of any sub)
1 loop of ultrasonic
1 loop of masked
1 loop of ultrasonic… and so on