LUFS Integrated (integrated loudness)

Definition

Integrated loudness is the average loudness of an entire program, calculated with the method of recommendation ITU-R BS.1770-4 and adopted by EBU R128:

1. K-weighting: each channel passes through two filters. The first is a +4 dB shelf above 1.5 kHz (it models the acoustic effect of the head); the other is a 2nd-order high-pass, the RLB curve, with a cutoff frequency near 38 Hz.
2. Blocks: the weighted signal is divided into 400 ms blocks with 75% overlap (a new block every 100 ms). For each channel i, the mean square z_ij of block j is calculated.
3. Block loudness: l_j = −0.691 + 10 · log10( Σ_i G_i · z_ij ), with G_i = 1.0 for left, right and center, G_i = 1.41 for the surrounds; the LFE channel is excluded.
4. Absolute gating: blocks with l_j < −70 LUFS are discarded.
5. Relative gating: the average loudness of the remaining blocks is calculated (average of the energies, not of the dB values) and the threshold Γ_r = average − 10 LU is set; blocks below Γ_r are discarded.
6. Integrated loudness: L_I = −0.691 + 10 · log10( Σ_i G_i · mean_j(z_ij) ) over the blocks that pass both gates.

The constant −0.691 compensates for the gain of the K-weighting at 1 kHz: a 997 Hz sine wave at 0 dBFS on a single channel measures −3.01 LUFS. Gating excludes silences and very quiet passages, which would otherwise pull the average down.

Parameters and units

• Unit: LUFS (Loudness Units relative to Full Scale, EBU terminology) = LKFS (ITU and ATSC terminology). Differences are expressed in LU; 1 LU = 1 dB.
• Broadcast: EBU R128 −23 LUFS ± 0.5 LU (± 1 LU for live programs); ATSC A/85 −24 LKFS.
• Streaming (playback normalization values): Spotify −14 LUFS (with −11 and −19 options), YouTube −14 LUFS, Apple Music −16 LUFS, Tidal −14 LUFS, Deezer −15 LUFS. For streaming, AES TD1004 indicates a level no higher than −16 LUFS and no lower than −20 LUFS.
• Typical music masters: pop/hip hop −10/−7 LUFS; club EDM −8/−5 LUFS; rock −11/−8 LUFS; jazz, acoustic, classical −18/−12 LUFS.
• Related quantities: short-term, momentary, LRA, PLR.

Musical function

Integrated loudness describes the perceived volume of an entire song with a single number and makes it possible to predict playback on platforms that normalize: a master at −8 LUFS on Spotify is turned down by 6 dB, while one at −14 LUFS stays unchanged. It is used to compare the mix with a reference at matched loudness, to decide how much limiting to apply in mastering and to even out the songs of an album. It is not an artistic goal in itself: the right value depends on the genre, the intended dynamics and the destination medium.

Practical example

Two masters of the same song:

After normalization the two masters have the same loudness, but B keeps 3.7 dB more dynamic margin and sounds more open on the transients.

Gating example: a 3:00 song has 8 s of initial silence (blocks below −80 LUFS, eliminated by the absolute gate) and a 15 s bridge at −24 LUFS. If the average of the remaining blocks is −11 LUFS, the relative threshold is −21 LUFS and the bridge is excluded from the calculation: the final integrated loudness is −10.6 LUFS.

Common mistakes

• Measuring only the chorus and calling the result integrated loudness.
• Comparing your own mix with references listened to at different loudness: the louder song always seems better.
• Chasing −14 LUFS as an absolute rule: a trap song at −14 integrated LUFS can come across as weak for the genre in playlists without normalization.
• Believing that platforms turn up quiet masters without limits: the increase is limited by the available true peak or requires a platform limiter.
• Using −23 LUFS, the broadcast value, as a target for streaming music.
• Measuring the file with tracks left in solo, added silences or incomplete fades.

How to check it

• App analysis: the Integrated loudness (BS.1770) row applies K-weighting, 400 ms blocks with a 100 ms step, the absolute gate at −70 LUFS and the relative gate at −10 LU on the left and right channels. The value is an estimate calculated in the browser; for official delivery it should be confirmed with a compliant meter.
• Dedicated meters: Youlean Loudness Meter, FabFilter Pro-L 2, iZotope Insight; all report Integrated, Short-term, Momentary, LRA and true peak.
• Procedure: export the whole song from start to finish, analyze it and compare the integrated loudness with the genre reference and with the platform's normalization value.
• Pairings: always read integrated loudness together with True peak (×4, BS.1770) and PLR (true peak − integrated LUFS).