-IEC type meters are a mix between DPM and RMS, created mainly for the purpose of interoperability.
-
-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 use to play it back.
-
-For the some home recording there is no real need for this level of interoperability and one does generally only need these meters when working in the broadcast industry.
-
-IEC-type also meters have certain characteristics (rise-time, ballistics) that are useful outside the context of broadcast.
-</p>
-
-<p>
-Their specification is very exact and as opposed to Ardour's DPM and RMS meters there are no customizable parameters.
-</p>
-
-<h3>VU meters</h3>
-<p>
-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 adhere to that spec, but for visual consistency displays VU meters as bar-graph rather than needle-style (more below).
-</p>
+ There are different metering standards, most of which are available in Ardour. In short:
+</p>
+
+<dl>
+ <dt>Digital peak-meter</dt>
+ <dd>A <dfn>Digital Peak Meter</dfn> 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 <abbr title="DeciBel Full
+ Scale">dBFS</abbr>, 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 <dfn>fall-off-time</dfn> and <dfn>peak-hold</dfn>, but no
+ exact specifications.
+ <p>
+ Various conventions for DPM fall-off times and dBFS line-up level can be
+ chosen in <kbd class="menu">Edit > Preferences > GUI</kbd>.
+ </p>
+ </dd>
+
+ <dt>RMS meters</dt>
+ <dd>An <dfn><abbr title="Root Mean Square">RMS</abbr>-type meter</dfn>
+ 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.
+ <ul>
+ <li><dfn>K20</dfn>: 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.</li>
+ <li><dfn>K14</dfn>: Same as K20 with scale aligned to -14 dBFS.</li>
+ <li><dfn>Peak + RMS</dfn>: standard RMS, customizable via
+ <kbd class="menu">Edit > Preferences > GUI > Metering</kbd></li>
+ </ul>
+ </dd>
+
+ <dt>IEC PPMs</dt>
+ <dd><dfn><abbr title="International Electrontechnical Commission">IEC</abbr>-type
+ <abbr title="Peak Programme Meters">PPM</abbr>s</dfn> are a mix between DPMs and
+ RMS meters, created mainly for the purpose of
+ interoperability. Many national and institutional varieties exist (<abbr
+ title="European Broadcasting Union">EBU</abbr>, <abbr title="British Broadcasting
+ Corporation">BBC</abbr>, <abbr title="Deutsche Industrie-Norm">DIN</abbr>).
+ <p>
+ 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.
+ </p>
+ <p>
+ 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.
+ </p>
+ <p>
+ Their specification is very exact, and consquently, there are no
+ customizable parameters.
+ </p>
+ </dd>
+
+ <dt>VU meters</dt>
+ <dd><dfn><abbr title="Volume Unit">VU</abbr> meters</dfn> 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).
+ </dd>
+</dl>