Are you taking the sound reading with fan on the SR-1 560? To me that would be the relevant sound level.
What is your ambient noise level and range of accuracy of your meter? I ask because mine is 30-130dBA and my ambinet is very close to 30dBA. Quietest times show graph of similar or slightly less flatline 30dBA with spikes bouncing to <33dBA.
I measure airflow almost against radiator / cooler .. and move it around some to find the most consistant flow level. I'm planning to make a flow tube with the end filled with straws to align airflow straight out. Tube will also be equipped with an inclined manometer built into it.