Make the readings comparable

Record the exact grille and measurement point, instrument, fan mode, nearby door and damper state, and the units reported. Repeat the observation at the same point after any change. Air velocity at one opening is not the total airflow of the system and cannot by itself prove that the whole room is balanced.

At St. Regis, the field record reported high velocity at a grille before the opening was modified (4408). A 200 mm opening was cut during the work (4419), and the later record reported 8.5 to 6 m/s on high speed and 4.5 m/s on low speed (4503). Those values describe that local check. They are not a target for another site, a duct flow-rate measurement or a guaranteed noise reduction.

Decide the next step from the pattern

If the noise changes strongly with fan mode, ask the specialist to inspect the grille, opening and connected route. If it persists with different modes or appears to come from a unit, ask for a mechanical and mounting check. Record whether an access opening or finish work would be needed. The contractor should explain what a proposed alteration is expected to change and which follow-up observations will test it. Keep subjective sound complaints alongside, not in place of, the recorded operating conditions.