Skip to content
Elephant Audio
Back to the reference index
Standard reference

EBU Tech 3341 — The Meter Specification Behind R 128

What is EBU Tech 3341, and what does it require of a meter?

EBU Tech 3341 defines EBU Mode metering — the loudness meter specification EBU R 128 requires compliance with. It fixes three measures: Momentary over a 0.4 s window, Short-term over 3 s, and gated Integrated Loudness. It also fixes the two permitted scales, the units, and a calibration check. The current version is V4, November 2023.

Source

Transcribed from the published standard, read 2026-09-30. Check it yourself

0.4 s
Momentary window
sliding, rectangular, ungated
3 s
Short-term window
sliding, rectangular
−70 LUFS
absolute gate
the relative gate sits 10 LU below the gated level
V4
in force
November 2023, drafted by EBU PLOUD

R 128 names the target. This names the instrument.

EBU R 128 sets the target — −23.0 LUFS, a true-peak ceiling, and the tolerances around them. It does not describe the meter that decides whether you hit it. That is this document, and R 128 makes compliance with it a requirement rather than a suggestion. A delivery can therefore be judged non-compliant because of the instrument rather than the mix.

Tech 3341 defines what the EBU calls EBU Mode: one agreed set of measures, time windows, scales and units, so that two meters from two manufacturers reading the same file agree, and so that a number quoted in an email means one thing. It was first published in 2010; the current version is V4, November 2023, drafted by the EBU's PLOUD group.

Most of it is decisions somebody has to make when building a meter. The clauses below are the ones that change what you do in a session, or explain a reading that looks wrong and is not.

The three time scales, and the letters on your meter

Clause 2.1 names three measures and abbreviates them M, S and I. All three are computed as ITU-R BS.1770 specifies; what this document fixes is the window around them.

  • Momentary (M) — a sliding rectangular window 0.4 s long. Not gated.
  • Short-term (S) — a sliding rectangular window 3 s long.
  • Integrated (I) — the whole programme or segment, gated as described in ITU-R BS.1770.
  • ⚠️ Momentary being ungated is the whole reason it moves during a pause while Integrated sits still. They are not two views of one number, and a Momentary peak is not a compliance failure.

What compliance actually obliges

“an EBU Mode compliant meter shall be able to measure and display the three main measures”
EBU Tech 3341, V4 (November 2023) — clause 2.8 — and they need not be displayed at the same time

What the gate excludes

Clause 2.3 summarises the gating that makes Integrated Loudness a foreground measurement rather than an average. Four rules, and the last is the one nobody expects:

  • An absolute 'silence' gate at −70 LUFS, used to compute the absolute-gated loudness level.
  • A relative gate 10 LU below that absolute-gated level.
  • The gate is applied to the loudness of 400 ms blocks, overlapping one another by 75%.
  • If a measurement ends part-way through a block, that incomplete block is discarded.
  • Because the relative threshold is itself derived from a loudness measurement, a live meter has to recalculate the threshold and re-apply it to every stored block each time the reading updates. That is why Integrated can move backwards as a programme plays, and why it is not a running average of what you have heard so far.

The two scales, and where zero is

A meter need not show a scale at all — clause 2.7 permits a numeric readout. If it shows one, it must be one of these two:

  • EBU +9 scale — −18.0 LU to +9.0 LU, which is −41.0 LUFS to −14.0 LUFS.
  • EBU +18 scale — −36.0 LU to +18.0 LU, which is −59.0 LUFS to −5.0 LUFS.
  • Zero on the relative scale is the target: −23.0 LUFS = 0.0 LU, as EBU R 128 defines it. A meter offering both scales must keep the target in the same place on the display whichever scale is shown.
  • The unit — LUFS or LU — must be displayed for all values and all scales, at all times. One Loudness Unit is one decibel.
  • ⚠️ This is where a screenshot misleads, and why the unit rule exists. The same numeral read as LUFS and as LU is always twenty-three decibels apart, whatever the numeral is.

A calibration check that takes a minute

Clause 2.9 gives a signal-level check anyone can run without test files. Feed a 1 kHz sine wave to both channels in phase, with its peak level at −18 dBFS. The meter should read −18.0 LUFS.

Why the two numbers match is worth understanding, because it shows the check is exercising the whole chain rather than reporting a coincidence: a sine wave's RMS sits about 3 dB below its peak, two identical in-phase channels sum to about 3 dB above one, and the K-weighting filters are close to unity at 1 kHz. The corrections cancel. We ran it against our own meter while writing this page, and it reads within 0.01 LU of the stated value.

The document attaches a caveat. A frequency of 1 kHz lies on a filter slope inside the algorithm, which makes the calibration more critical than it needs to be with respect to how accurately that filter is implemented. Treat it as a check of your signal path, not as a precision test of the meter. The alignment procedure itself is defined in the EBU's Guidelines for Production.

Loudness Range, and why it says nothing about a thirty-second spot

Clause 2.4 makes Loudness Range supplementary to Integrated Loudness, and attaches a limitation that matters more in advertising than anywhere else:

  • LRA is based on a loudness-level measurement as specified in ITU-R BS.1770, and describes how loudness varies on a macroscopic time scale.
  • The LRA computation resets whenever the Integrated Loudness measurement resets. They are one instrument, not two.
  • During the first 60 s of an LRA measurement the displayed value is not yet to be considered stable, and the meter is expected to indicate as much.
  • The full LRA specification is not in this document at all. It is EBU Tech 3342.
  • ⚠️ Most advertising is shorter than 60 s. An LRA figure quoted on a 30-second spot is a number this specification says is not yet stable — the same conclusion EBU R 128 reaches when it declines to recommend LRA below one minute.

Two details that catch people out

  • The LFE channel is not included in the ITU-R BS.1770 measurement. Clause 2.10 records that the appropriate weighting has been the subject of discussion and investigation, and that the EBU recommends that if LFE were included it should be weighted +10 dB, to compensate for its playback gain being 10 dB higher across its frequency range.
  • A compliant meter must let you start, pause and continue the measurement of Integrated Loudness and Loudness Range, and reset both simultaneously. A control that resets one without the other is not compliant.
  • The test signals are published by the EBU and synthesised at 48 kHz. Clause 2.9 warns that test signals 15 to 23 are very loud and should not be listened to at normal playback levels.

The sources

Read directly on 2026-09-30:

Common questions

What does 'EBU Mode' on my loudness meter mean?

It means the meter implements EBU Tech 3341. Concretely, it can measure and display Momentary, Short-term and Integrated Loudness, uses a 0.4 s window for Momentary and 3 s for Short-term, gates the Integrated measurement as ITU-R BS.1770 specifies, and always shows the unit alongside the number. EBU R 128 requires compliance with it, so a meter without EBU Mode cannot demonstrate R 128 compliance.

Why does my Momentary reading jump when Integrated barely moves?

Because Momentary is not gated and Integrated is. Momentary reports a 0.4 s sliding window of whatever is present, including a single loud transient. Integrated discards blocks below an absolute gate at −70 LUFS and a relative gate 10 LU below the gated level, so it describes foreground loudness across the programme. A Momentary peak is not a compliance failure; the Integrated figure is what a delivery spec constrains.

Is 0 LU the same as −23 LUFS?

Yes, on an EBU Mode meter. Tech 3341 fixes zero on the relative scale at the EBU R 128 target, so 0.0 LU is −23.0 LUFS and one Loudness Unit is one decibel. That is also why the same numeral means very different things in the two units — read as LUFS and as LU it is always twenty-three decibels apart, which is exactly why the specification requires the unit to be on screen at all times.

My Loudness Range reading keeps changing on a short spot. Is the meter broken?

No. Tech 3341 states that during the first 60 s of an LRA measurement the displayed value is not yet to be considered stable. Most advertising is shorter than that, so on a 30-second spot the reading never reaches the point where the specification considers it meaningful. Use Integrated Loudness and Short-term maxima for short-form, which is what the short-form recommendations actually constrain.

How do I check my meter is reading correctly?

Clause 2.9 gives a check that needs no test files: a 1 kHz sine wave fed to both channels in phase, peaking at −18 dBFS, should read −18.0 LUFS. For a real verification, the EBU publishes a set of test signals synthesised at 48 kHz, and Tech 3342 adds more for Loudness Range. Be careful with signals 15 to 23, which the document warns are very loud.

Next

This page is the lookup. Broadcast and Streaming Loudness Specs for Commercials is the explanation behind it.

Reading disagrees with the broadcaster's?

Send the file and the spec sheet. Every deliverable comes back measured individually with the report attached, so a rejection can be answered with a number rather than an argument.

Send your delivery spec WhatsApp the studio

Studio credit

Elephant Audio

Audio production · Sound design · Music production

LahoreEngineering sound since 2018

Last updated:

Send your delivery spec