When I measure it from 15-20cm, 2kHz is 49.5dB and 3kHz is 52.4dB. When I get my iPhone's microphone closer to the source, the difference is less than 4dB. What does it mean?check with a frequency genrator if 3khz is louder or quieter than 2khz. maybe use a dezibel measurement app if you cant decide by ear.
anyway both are pretty good.