How to find out if the speakers are 20khz compatible? + need to be a native speaker?

[Shannon]

If at any time you start hearing static while the frequency is above 10 kHz, then your speaker may not be able to reproduce ultrasonic pitches.  Usually it will be the last several seconds that produce that static if there is an issue.  

If you didn't get static, then your speaker is good to go.

Ok. Thanks. I am not sure about that. I can hear something when I increase the volume while the frequency ist above 10khz. But for the last few seconds I can hear also a static.

In the FrequenSee app I can see something for all the time. But this doesn't matter?

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Can someone recomment a cheap small speaker which ist 20khz compatible and which is mobile and easy to transport. So that I can use it where-ever I sleep and work?

Speakers and headphones can be classified in two broad categories:  Those that can effectively reproduce the full range of CD quality sound (20 Hz to 20 kHz) and those that cannot.

If running the speaker test results in static for the last few seconds, you are dealing with something that cannot effectively reproduce ultrasonic audio.  That means the part of it that actually creates the sound is being overloaded, and the result is static, which is random distortion.  That does not allow for the subliminal audio to be understood by your subconscious mind.

If you are playing it very loudly and get that static, but lowering the volume to some degree makes the static go away, then you are dealing with a speaker or headphone that is of the bare minimum level of quality for reproducing ultrasonic audio, and you can usually use those alright.  They typically give some crackling, but not constant static.  They're not the best, but they will do.  

The best is what you play the speaker test on, and once the audio goes past 10-12 kHz, you hear absolutely nothing but the audio from the speaker (if you can hear ultrasonic audio).

FrequenSee will show you the pitch of the audio, but not the distortion level.  It is the distortion level that we are concerned about here.