Chapter 2: Line Levels, Headroom and Metering Flashcards
Describe Line Level.
Line level is the ‘nominal signal’ level, (expressed in dB against a standard reference voltage.)
What is a Noise floor?
The level of noise inherent in a system.
Describe Headroom and give a reason for wanting it.
Headroom is defined as the difference between nominal level and maximum output. It is good to use as a safety zone, allowing for large dynamics not to distort the signal.
What is a VU meter and what does the VU stand for?
A voltmeter is a voltmeter of specified transient response, VU stands for Volume units.
What does RMS voltage stand for and what is it?
Route Means Squared- Shows the average level of a signal, more like how we perceive it.
+3 VU is equal to +4dBu, true or false?
False, the VU scale goes from -20 to + 3 VU, but +4dBu is equal to 0VU.
Why don’t transient/percussive sounds register much on a VU meter?
Because VU meters measure average levels and are better at measuring sustained levels. The have a slow response and fallback time (of about 300 milliseconds).
Which level would engineers use as a ‘zero reference level’, 0dBu, 0dBv or 0VU?
0VU (+4dBu or -10dBv)
What does PPM stand for and what unit does it use?
PPM stands for Peak Program Meter and is calibrated in dB.
Does a PPM meter react to transients faster or slower than a VU meter?
A PPM reacts quicker (10ms instead of 300ms) and therefore is not a measurement of the perceived volume.
Does a PPM have a faster or slower fall time than a VU meter.
The PPM fall/release time is slower than a VU meter, this is so that the fast response can be easily registered by our eyes.
Why don’t digital systems use VU or PPM metering?
Because even the briefest of transient overloads is clearly audible on a digital system.
What is the maximum quantisation/volume level of digital meters?
0dBfs (Full-Scale).
What does 0dBFS mean, with regards to Bits?
Nearly all 16 or 24 bits are ON (1).
Is there a way for DAWs to internally handle digital audio levels above 0dBFS?
Yes, a 32-bit floating point-resolution can be used for the audio processing. This means you can get much higher values and therefore a larger dynamic range.
