Audio Normalizer (LUFS & Peak)

About the Audio Normalizer (LUFS & Peak)

Bring a recording to a standard loudness: −14 LUFS for music on streaming services, −16 LUFS for podcasts, −23 LUFS for broadcast (EBU R 128) — or set the loudest peak to a level, or choose your own loudness. The page measures the file first, exactly as ITU-R BS.1770-5 describes (K-weighting and gating), and shows its integrated loudness, loudness range, true peak, sample peak and loudest moments.

It then applies one fixed gain to the whole file, so the balance between quiet and loud passages stays as it was. Where that gain would push peaks over the true-peak ceiling (−1 dBTP by default), a look-ahead true-peak limiter holds them under it; or turn the limiter off and let the gain stop at the ceiling instead. Listen to 15 seconds of the loudest part before and after to compare.

The result keeps the file’s format where the browser can write it (MP3 stays MP3, WAV stays WAV, FLAC stays FLAC), and a video keeps its picture, copied unchanged, with only the sound re-encoded. Afterwards the page decodes the finished file and measures it again, so the “after” values are those of the file you download. Nothing is uploaded.

Without a pass, the result is a free preview: the first half of the normalised sound (up to 30 seconds) with a short MySmartCoPilot chime every 10 seconds — for a video, its sound alone — while the measured loudness, peaks and gain stay hidden. The full file and every measurement, before and after, come with a pass, or after unlocking this result.

Which target to choose

• Streaming, −14 LUFS: Spotify plays music at −14 LUFS in its normal setting and recommends masters at −14 LUFS integrated with true peaks below −1 dBTP — or below −2 dBTP for masters louder than −14 LUFS (Spotify for Artists).
• Podcast, −16 LUFS: Apple recommends that podcast audio stays around −16 LKFS, give or take 1 dB, with true peaks not above −1 dBFS (Apple Podcasts audio requirements).
• Broadcast, −23 LUFS: EBU R 128 normalises programmes to −23.0 LUFS with true peaks of at most −1 dBTP (EBU R 128).
• Peak level: the loudest peak at −1 dBFS (or another level) — the classic “normalise” of audio editors. It does not make files equally loud, only equally peaky.

LUFS and LKFS are the same unit. Services that normalise playback turn loud files down anyway, so making a file louder than its target gains nothing and costs dynamics.

How it is measured

Loudness follows ITU-R BS.1770-5: each channel is K-weighted (a high shelf that models the head, then a high-pass), mean squares are taken over 400 ms blocks every 100 ms, blocks below −70 LUFS are ignored, then blocks more than 10 LU below the rest. Loudness range is measured as EBU Tech 3342 defines it, from short-term (3 s) loudness. True peak uses the 4× over-sampling filter of BS.1770-5 Annex 2, which finds peaks between the samples that a sample meter misses. The meter is checked against the test signals of EBU Tech 3341 and Tech 3342.

What the limiter does — and does not do

The limiter looks 5 ms ahead and turns the gain down smoothly just before a peak that would pass the ceiling, then lets it recover over about 150 ms. It counts inter-sample peaks too, so the result stays under the ceiling after digital-to-analogue conversion. Below the ceiling it changes nothing.

It is not a compressor: the gain is the same for the whole file, so quiet passages stay quiet relative to loud ones. If a target needs several decibels of limiting, the page says so — that much limiting can sound squashed, and a lower target is often better.

Limitations

• Lossy encoders (MP3, AAC, Opus) can move peaks by a few tenths of a decibel; the page measures the finished file and says if a peak ended up above the ceiling. A ceiling of −2 dBTP leaves room for that.
• One gain for the whole file: it does not even out a recording whose parts differ in level (that needs compression or manual editing).
• Ogg Vorbis and Opus files cannot be written here, so they are saved as MP3 (or another format you choose); a video’s sound is always re-encoded.
• One file at a time. Copy-protected files (DRM) and codecs browsers cannot decode cannot be normalised.

Privacy

Everything happens in your browser. What you enter or open here is not uploaded or stored by MySmartCoPilot. The audio engine and the encoders download from MySmartCoPilot the first time you open a file. Your audio and video are never uploaded.