Audio Visual Resources Blog dBu vs. dBFS

Which should rule DSP meters?AV 9000 Standard Checklist Item Under Test: For audio conference systems, confirm microphone input gain settings are such that the "standard talker" (60 dB SPA at 1 m, IEC 60268-16), positioned at each talker position in the room, produces a nominal "0 dB" level at the input of the mixer bus of the audio conference DSP device. If there is local reinforcement ("mix-minus"), AGC and ALC may need to be restricted. Record test results as pass/fail. Record level across analog telephone line. Inspect DSP mixer telephone line levels, both transmit and receive, when normal speech is encountered in the room.Testing Reasoning: In order to provide optimal signal to noise ratio on microphone channels, while still allowing for adequate headroom, the AV 9000 standard suggests setting all audio levels (microphones, conference transmit, conference receive, etc.) in a DSP mixer to "0 dB". The reason "0 dB" is in quotations is because sometimes it is a solid yellow, sometimes it is actually 0 dB read on a meter, and sometimes it might be -20 dBFS. As common as "0 dB" (typically 0 dBu) is in today's DSP mixers, I think dBFS may be more informative and useful to the site file programmer.Read More