Metering Flashcards
What do VU meters indicate?
What unit(s) of measurement do they use?
Are they fast or slow?
Slow, showing the RMS levels not the peak
uses the decibel scale but also has a second scale indicated in percentage of volume.
What does the “VU” stand for in VU meter?
Volume unit
What is the range of the dB scale in a VU meter?
Range: -20 dB VU to +3 dB VU
How long does it take for a needle to reach 0 VU from -20 VU?
300 ms +/- 10%
What is the standard overshoot on a VU meter?
1 - 1.5%
What does the LED light indicate on a VU meter?
it’s a peak light, that light up when a predetermined transient level is detected (usually about 6-12 dB above the actual instrument)
What type of meter is this?
BBC PPM meter
In a PPM (BBC) meter, what does each mark represent?
each of the markings (1-7) represent a 4 dB change
with the exception of 0-1 which is a 6dB change
and 7-8, which is a 2dB change
In a PPM meter, which marking corresponds to 0dBu?
Mark 4
What does a Digital Peak Meter (DPM) display?
absolute maximum signal of the raw samples in the PCM signal for a given time
What is the scale range of a DIN meter?
from - 50 dB to +50 dB
In a DIN meter, what is the value of the 0 dB marking in dBu and in Volts RMS?
+6 dBu which is 1.55 Volts RMS
In a DIN meter, where is the marking for the test level?
-9 dB
In both Nordic and DIN PPM meters, where is full modulation on the meter and how many volts is “full modulation’?
Full modulation is at the edge of the red area
1.55 V RMS
How many volts is the 0dB (test marking) on a Nordic PPM meter?
0.775 Volts RMS
How are DPMs calibrated?
to 0dBFS or the max level that can be represented digitally in a given system
What is a True-Peak Meter?
A digital peak meter with additional data pre-processing.
How is the audio signal different in a True-Peak meter compared to a DPM?
TPM audio signal is up-sampled, usually by a factor of 4, to take intersample peaks into account.
What scale and unit of measurement do true-peak meters use?
dBTP (decibels relative to full scale, measured as a true-peak value instead of dBFS.
dBTP and dBFS are identical except that dBTP may be larger than zero (full-scale) to indicate peaks.
To comply with EBU R128, how loud should your normalised content be? What is the permitted deviation fromt eh target level?
Target Level: -23.0 LUFS
permitted deviation shall generally not exceed ±1.0 LU
What do LU and LUFS stand for?
Which broadcasting body uses these as standard measuring units?
Loudness Unit
Loudness Unit, referenced to Full Scale
EBU R128 (European Broadcasting Union)
What is the EBU R 128?
The European Broadcasting Union guideline for loudness normalization and permitted maximum level of audio signals, most recently revised in 2014.
What are intersample peaks?
created as part of the digital to analogue conversion where the reconstruction of a sound wave exceeds 0dBFS to the true peak of the sound occurs between digital samples and thus gets “squared off”, creating distortion
even if not clipping in the digital domain, can cause distortion when converted back to analogue
What does PPM stand for?
Peak Program Meter
