Why can't we hear dog whistles?

Answer: Frequency too high for human ears

Frequency too high for human ears ✓ — Correct! Dog whistles produce ultrasonic sounds above 20,000 Hz (20 kHz), higher than the upper limit of human hearing (about 20 kHz). Dogs can hear up to 65 kHz, so they hear the whistle clearly while humans hear nothing. Frequency, not volume, makes it inaudible to us.

Whistles are designed too quietly — Wrong. Dog whistles aren't quiet—they're loud at frequencies humans can't hear. Dogs hear them clearly because they detect higher frequencies.

Dogs have better hearing organs — Wrong. Dogs do have better high-frequency hearing, but the specific reason we can't hear dog whistles is that they operate above human hearing range.