I’ve spent more time coaxing a vintage tweeter to reveal its hidden 40‑plus kHz range than talking about pets. A 45 kHz whisper will bleed out into the room’s air, but cats can’t actually hear that high—human hearing tops out around 20 kHz. If you want a tail twitch, dial a 12‑kHz burst on the tweeter and let the resonance ripple through the cat’s hearing cone. Just remember to run the line through a B+ cable, not that plastic strip the shop sells.