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
What meter is the most useful for the mastering process?
The Dorrough Loudness Meter
What does the Dorrough Loudness Meter display?
What is it’s response time like?
diplays both average and peak elvels in a single readout with a very fast response time to accurately reflect incoming transients
A “EBU Mode” meter offers which two scales, for the user to select?
EBU +9 scale and EBU +18 scale
What is the range of EBU +9 scale?
-18.0 LU to +9.0 LU (-41.0 LUFS to -14.0 LUFS)
What is the range of the EBU +18 scale?
-36.0 LU to +18.0 LU (-59.0 LUFS to -5.0 LUFS)
What is a VU meter?
is a device displaying a representation of the signal level in audio equipment
What are ballistics in metering?
how fast the meter responds to the sound it’s measuring
What is a goniometer/lissajous meter?
a meter that plots the signal on a 2D area using lissajous figures to show the correlation of audio information between the two axes (audio channels, or phases) becomes apparent
What type of meter is this?
bar VU meter
benefits of VU meters?
slow response that behaves similarly to human hearing
recommended reference for VU meter?
-18 dBFS
What is crest factor?
Crest factor is teh ratio of the difference between peak level and RMS of a waveform.
What is a real-time analyzer (RTA) / spectrum analyser?
measures and displays the frequency spectrum of an audio signal (input) in real time using the magnitude of an input signal vs. the frequency.
what is a vector scope?
used to measure the difference between channels of stereo audio signals displayed on an X-Y plot. One channel drives the horizontal deflection of the display while the other drives the vertical. Reveals the relationship between the two signals.
what is an oscilloscope?
produces a two dimentional plot of one or more signals as a function of time.
should be calibrated for both time and level
true peak
oversampling x 4
DEF: LUFS
Loudness Unit Reference to Full Scale
measurement unit instroducted as part of the EBU R128 Standard
DEF: Momentary Loudness (M)
Uses an RMS window of 400 miliseconds, therefore it shows quick fluctuations in loudness
DEF: Short Term Loudness (S)
Uses an RMS window of 3 seconds and provides more stable loudness measurements
DEF: Integrated Loudness (I)
Shows overall loudness, and is affected by the whole track from beginning of playback until you reset it by clicking the value field
DEF: Loudness Range Meter (LR)
shows the input loudness range. The loudness meter, LU, follows the ITU-R BS 1770-1 and EBU 3342 specs so the LU represents -23 dbFS.
What is LU?
Loudness units
What is the Maximum Permitted True Peak Level of a programme during production?
Must not exceed -1 dBTP
What scale do true peak meters use?
dBTP
decibels relative to full scale, measured as true-peak value instead of dBFS.
May be larger than 0 full scale to indicate peaks.
What is a K-System meter?
has a peak meter and an RMS meter for each stereo channel.
RMS measures average signal strength. Which is the focus rather than peak meter, which is primarily used to detect clipping.
Both peak and RMS meters
What are the three scales used in the K-System?
What is their purpose?
K12, K14, K20
each provides different amound of head room above 0dB
