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+
+Introduction
+
+ An engineer reading and using audio level meters compares to a musician
+ reading or writing sheet-music. Just like there are virtuoso musicians
+ who can't read a single note, there are great sound-engineers who just
+ go by their ears and produce great mixes and masters without ever looking
+ at a single meter.
+
+
+ Yet, if you want to work in or with the broadcast industry, it is
+ usually unavoidable to use meters.
+
+
+ Audio level meters are very powerful tools that are useful in every
+ part of the entire production chain:
+
+
+ - When tracking, meters are used to ensure that the input
+ signal does not overload and maintains reasonable
+ headroom.
+ - Meters offer a quick visual indication of a
+ activity when working with a large number of tracks.
+ - During mixing, meters provide an rough estimate of the
+ loudness of each track.
+ - At the mastering stage, meters are used to check
+ compliance with upstream level and loudness
+ standards and to optimize the loudness range
+ for a given medium.
+
+
+Meter Types
+
+ A general treatise on metering is beyond the scope of this
+ manual. It is a complex subject with a history...
+ For background information and further reading we recommend:
+
+
+
+
+ There are different metering standards, most of which are available in Ardour. In short:
+
+
+
+ - Digital peak-meter
+ - A Digital Peak Meter displays the absolute maximum signal
+ of the raw audio PCM signal (for a given time). It is commonly used when
+ tracking to make sure the recorded audio never clips. To that end, DPMs
+ are always calibrated to 0 dBFS, or the maximum level that can be represented digitally
+ in a given system. This value has no musical reason whatsoever and depends
+ only on the properties of the signal chain or target medium. There are
+ conventions for fall-off-time and peak-hold, but no
+ exact specifications.
+
+ Various conventions for DPM fall-off times and dBFS line-up level can be
+ chosen in .
+
+
+
+ - RMS meters
+ - An RMS-type meter
+ is an averaging meter that looks at the energy in the signal. It
+ provides a general indication of loudness as perceived by humans. Ardour
+ features three RMS meters, all of which offer additonal peak indication.
+
+ - K20: A meter according to the K-system introduced by Bob
+ Katz, scale aligned to -20 dBFS, rise/fall times and color schema
+ according to spec.
+ - K14: Same as K20 with scale aligned to -14 dBFS.
+ - K12: Same as K20 with scale aligned to -12 dBFS (since 3.5.143).
+ - Peak + RMS: standard RMS, customizable via
+
+
+
+
+ - IEC PPMs
+ - IEC-type
+ PPMs are a mix between DPMs and
+ RMS meters, created mainly for the purpose of
+ interoperability. Many national and institutional varieties exist (EBU, BBC, DIN).
+
+ These loudness and metering standards provide a common point of
+ reference which is used by broadcasters in particular so that the
+ interchange of material is uniform across their sphere of influence,
+ regardless of the equipment used to play it back.
+
+
+ For home recording, there is no real need for this level of
+ interoperability, and these meters are only strictly required when
+ working in or with the broadcast industry. However, IEC-type meters have
+ certain characteristics (rise-time, ballistics) that make them useful
+ outside the context of broadcast.
+
+
+ Their specification is very exact, and consquently, there are no
+ customizable parameters.
+
+
+
+ - VU meters
+ - VU meters are the dinosaurs (1939)
+ amongst the meters. They react very slowly, averaging out peaks.
+ Their specification is very strict (300ms rise-time, 1 - 1.5% overshoot,
+ flat frequency response). Ardour's VU meter adheres to that spec, but for
+ visual consistency it is displayed as a bar-graph rather than needle-style
+ (more below).
+
+
+
+Ardour Specifics
+
+
+
+ Meters are available in various places in ardour:
+
+
+ - The mixer window features fixed height meters for each channel strip.
+ - There are small (narrow) meters on each track-header in the editor window.
+ - There are variable height meters in the meterbridge window.
+ - Optionally, a fixed-size master meter can be displayed in the main toolbar.
+ - Various other locations (file import, sends) have level-meters.
+
+
+ They all share the same configuration and color-theme which is available in
+ preferences and the theme-manager. Settings for the Peak and RMS+Peak meters
+ as well as VU meter standards are found in
+ .
+
+
+ The type of meter and the metering point (the place in the signal chain
+ where the meter taps the signal) are configurable in the context menu of each meter.
+ Depending on the settings, the metering point is also accessible via a button in
+ each Mixer strip.
+
+
+
+ Regardless of meter type and standard the meter display will highlight red if
+ the signal on the given channel exceeds the configured peak threshold.
+
+
+ Left on the peak-indicator button resets the
+ peak-hold indicator of a single channel.
+ Left resets a whole group, and
+ Left resets all meters.
+
+
+Overview of meter types
+
+
+ The figure on the left shows all available meter-types in Ardour 3.4 when fed with a
+ -18 dBFS 1 kHz sine wave.
+
+
+
+
+
+
+ Due to layout concerns and consistent look&feel all meters available in
+ Ardour itself are bar-graph type meters. Corresponding needle-style meters
+ — which take up more visual screen space — are available as
+ LV2 plugins (see image on the right):
+ meters.lv2.
+
+