4 An engineer reading and using audio level meters compares to a musician
5 reading or writing sheet-music. Just like there are virtuoso musicians
6 who can't read a single note, there are great sound-engineers who just
7 go by their ears and produce great mixes and masters without ever looking
11 Yet, in order to work in or with the broadcast industry, it is
12 usually unavoidable to use meters.
15 Audio level meters are very powerful tools that are useful in every
16 part of the entire production chain:
19 <li>When tracking, meters are used to ensure that the input
20 signal does not <dfn>overload</dfn> and maintains reasonable
21 <dfn>headroom</dfn>.</li>
22 <li>Meters offer a <dfn>quick visual indication</dfn> of an
23 activity when working with a large number of tracks.</li>
24 <li>During mixing, meters provide an rough estimate of the
25 <dfn>loudness</dfn> of each track.</li>
26 <li>At the mastering stage, meters are used to check
27 compliance with upstream <dfn>level</dfn> and <dfn>loudness
28 standards</dfn> and to optimize the <dfn>loudness range</dfn>
29 for a given medium.</li>
34 A general treatise on metering is beyond the scope of this
35 manual. It is a complex subject with a history…
36 For background information and further reading we recommend:
39 <li><a href="http://www.digido.com/how-to-make-better-recordings-part-2.html">How To Make Better Recordings in the 21st Century—An Integrated Approach to Metering, Monitoring, and Leveling Practices</a> by Bob Katz. Has a good historic overview of meters and motivates the K-meter</li>
40 <li><a href="https://en.wikipedia.org/wiki/Peak_programme_meter#Table_of_characteristics">Wikipedia: Peak programme meter</a>—overview of meter types.</li>
41 <li>"Audio Metering: Measurements, Standards and Practice: Measurements, Standards and Practics", by Eddy Brixen. ISBN: 0240814673</li>
42 <li>"Art of Digital Audio", by John Watkinson. ISBN: 0240515870</li>
46 There are different metering standards, most of which are available in Ardour. In short:
50 <tr><th>Digital peak-meter</th>
51 <td>A <dfn>Digital Peak Meter</dfn> displays the absolute maximum signal
52 of the raw audio PCM signal (for a given time). It is commonly used when
53 tracking to make sure the recorded audio never clips. To that end, DPMs
54 are always calibrated to 0 <abbr title="DeciBel Full
55 Scale">dBFS</abbr>, or the maximum level that can be represented digitally
56 in a given system. This value has no musical reason whatsoever and depends
57 only on the properties of the signal chain or target medium. There are
58 conventions for <dfn>fall-off-time</dfn> and <dfn>peak-hold</dfn>, but no
61 Various conventions for DPM fall-off times and dBFS line-up level can be
62 chosen in <kbd class="menu">Edit > Preferences > Metering</kbd>.
66 <tr><th>RMS meters</th>
67 <td>An <dfn><abbr title="Root Mean Square">RMS</abbr>-type meter</dfn>
68 is an averaging meter that looks at the energy in the signal. It
69 provides a general indication of loudness as perceived by humans. Ardour
70 features three RMS meters, all of which offer additonal peak indication.
72 <li><dfn>K20</dfn>: A meter according to the K-system introduced by Bob
73 Katz, scale aligned to -20 dBFS, rise/fall times and color schema
74 according to spec.</li>
75 <li><dfn>K14</dfn>: Same as K20 with scale aligned to -14 dBFS.</li>
76 <li><dfn>K12</dfn>: Same as K20 with scale aligned to -12 dBFS (since 3.5.143).</li>
77 <li><dfn>Peak + RMS</dfn>: standard RMS, customizable via
78 <kbd class="menu">Edit > Preferences > Metering</kbd></li>
83 <td><dfn><abbr title="International Electrontechnical Commission">IEC</abbr>-type
84 <abbr title="Peak Programme Meters">PPM</abbr>s</dfn> are a mix between DPMs and
85 RMS meters, created mainly for the purpose of
86 interoperability. Many national and institutional varieties exist (<abbr
87 title="European Broadcasting Union">EBU</abbr>, <abbr title="British Broadcasting
88 Corporation">BBC</abbr>, <abbr title="Deutsche Industrie-Norm">DIN</abbr>).
90 These loudness and metering standards provide a common point of
91 reference which is used by broadcasters in particular so that the
92 interchange of material is uniform across their sphere of influence,
93 regardless of the equipment used to play it back.
96 For home recording, there is no real need for this level of
97 interoperability, and these meters are only strictly required when
98 working in or with the broadcast industry. However, IEC-type meters have
99 certain characteristics (rise-time, ballistics) that make them useful
100 outside the context of broadcast.
103 Their specification is very exact, and consquently, there are no
104 customizable parameters.
108 <tr><th>VU meters</th>
109 <td><dfn><abbr title="Volume Unit">VU</abbr> meters</dfn> are the dinosaurs (1939)
110 amongst the meters. They react very slowly, averaging out peaks.
111 Their specification is very strict (300ms rise-time, 1–1.5% overshoot,
112 flat frequency response). Ardour's VU meter adheres to that spec, but for
113 visual consistency it is displayed as a bar-graph rather than needle-style
118 <h2>Ardour Specifics</h2>
120 <figure class="right">
121 <img src="/images/mixer-meter-context-menu.png" alt="mixer strip meter context menu">
123 Mixer strip meter context menu
128 Meters are available in various places in Ardour:
131 <li>The mixer window features fixed height meters for each <dfn>channel strip</dfn>.</li>
132 <li>There are small (narrow) meters on each <dfn>track-header</dfn> in the editor window.</li>
133 <li>There are variable height meters in the <dfn>meterbridge window</dfn>.</li>
134 <li>Optionally, a fixed-size <dfn>master meter</dfn> can be displayed in the main toolbar.</li>
135 <li>Various other locations (<dfn>file import</dfn>, <dfn>sends</dfn>) have level-meters.</li>
138 They all share the same configuration and color-theme which is available in
139 preferences and the theme-manager. Settings for the Peak and RMS+Peak meters
140 as well as VU meter standards are found in
141 <kbd class="menu">Edit > Preferences > Metering</kbd>.
145 The type of meter and the <dfn>metering point</dfn> (the place in the signal chain
146 where the meter taps the signal) are configurable in the context menu of each meter.
147 Depending on the <kbd class="menu">Edit > Preferences > Mixer</kbd> settings,
148 the metering point is also accessible via a button in each Mixer strip.
152 Regardless of meter type and standard the meter display will highlight red if
153 the signal on the given channel exceeds the configured peak threshold.
156 <kbd class="mouse">Left</kbd> clicking on the peak-indicator button resets the
157 <dfn>peak-hold indicator</dfn> of a single channel.<br>
158 <kbd class="mod1 mouse">Left</kbd> clicking resets a whole <dfn>group</dfn>, and<br/>
159 <kbd class="mod13 mouse">Left</kbd> clicking resets all meters.
162 <h2>Overview of meter types</h2>
164 <figure class="left">
165 <img class="mini" src="/images/meter-types-18.png" alt="Bar-graph meters in Ardour">
167 Bar-graph meters in Ardour
171 <figure class="right">
172 <img class="mini" src="/images/needle-meters-18.png" alt="Needle-style meters as external LV2 plugins">
174 Needle-style meters as external LV2 plugins
179 The figure on the left shows all available meter-types in Ardour 3.4 when fed with a
180 -18 dBFS 1 kHz sine wave.
184 Due to layout concerns and consistent look and feel all meters available in
185 Ardour itself are bar-graph type meters. Corresponding needle-style
186 meters—which take up more visual screen space—are available as
187 LV2 plugins (see image on the right):
188 <a href="https://github.com/x42/meters.lv2/">meters.lv2</a>.