An existing recording from normal use may help distinguish the sound and timing. It should not require another flush, opening the unit or approaching wet electrical equipment.
What the observation means
Sound alone cannot identify an internal part, and microphone placement can exaggerate vibration. The fixture used and water-level result remain important.
A useful next step
Share the recording with a factual description if useful. Stop further use for abnormal operation. Do not continue running the pump for a clearer clip or place a phone inside a concealed service space.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.