Like many of the regulations the gov't writes, it is wordy to the point of confusion. They never learned to kiss.
Try
http://asq.org/quality-progress/2010/11/measure-for-measure/where-does-it-say-that.html. This article was written by Jay Bucher (RIP), whose was pretty knowledgeable in FDA-related calibration areas. Also, from a different author, this presentation:
http://www.ombuenterprises.com/LibraryPDFs/Medical_Device_Calibration_Program.pdf.
Looks like it's just a calibration of a mic. The results should state the accuracy--did the UUT measure the standard within the UUT's tolerance--and did it do it with precision--did several measurements reproduce the same result--and state these results in the calibration report. The requirements for accuracy (allowable error) and precision should be stated in the calibration procedure. Was/were your standards good enough for the calibration.
If it was out of tolerance, what did you do about all the measurements it made on your product since it was last calibrated or known to be good.
I don't see this as any different than Z540-1, .3, 17025, etc..
Accuracy and precision define the requirements for a measurement and its associated equipment.