FAQs from Rohde & Schwarz

Meaning of 0dBFS and 0dBr


What do 0dBFS and 0dBr mean in connection with the UPV, UPD and UPL audio analyzers?


The term "dBFS" used in our UPV,UPD and UPL instruments refers to the definition in the AES17 standard. There, full-scale is defined as the amplitude of a sine wave whose positive peak value reaches the maximum positive value.

This definition is now valid for both the peak value and the RMS value. As a consequence, in the digital domain for a sine wave (versus analog sine waves), the peak value in FS or dBFS is equal to the RMS.

On the other hand, a square signal which is set to maximum gain reaches an RMS of +3.0 dBFS.

dBr is an internal unit of the UPV/UPD/UPL instruments. Its reference can be chosen by the user. The instruments have no fixed relationship between dBr and dBFS. 0dBr = function value (e.g. RMS value or peak value). The relationship is determined by the reference value entered by the user in the corresponding configuration panel.