11-03-2014, 10:55 PM
You are supposed to listen to the ultrasonic like the instruction say ie a notch lower than the masked one. If you hear the buzzing sound there are 2 possibilities, your speaker doesn't pass the requirement or you have a special hearing ( you hear ultrasonic). Try the ultrasonic on a good headphone to know if you have a special hearing . The cost of a headphone/earphone that pass the requirement is usually much lower. So you have a better chance to have one. It's not recommended to listen to the ultrasonic on headphone though, I just do that as a test. For example I hear the buzzing sound from laptop speaker but not on my AKG K272 (even with a high volume) so I know it's my speaker that doesn't pass the requirement.
