What is the first thing to try for a noisy pool pump?

A rubber pad is the first thing to try. Most pool pump noise is vibration transmitted through the concrete or pad, so a thick rubber mat or anti-vibration pads under the pump feet decouple that vibration, dropping noise noticeably without affecting performance. Also check for loose screws, a cracked base, or debris rattling inside. Don’t buy a new pump yet—start with the $20 fix.