BS.1770-4 Explained: The Standard Behind Professional Loudness

ITU-R BS.1770-4 is the international standard for measuring audio programme loudness. Published by the International Telecommunication Union, it defines the algorithms used to calculate integrated loudness, true peak level, and loudness range.

What BS.1770-4 Specifies

The standard defines a specific signal chain for loudness measurement:

1. **K-frequency weighting**: A two-stage filter that approximates the acoustic effects of the human head.
2. **Mean square calculation**: Per-channel energy measurement.
3. **Channel-weighted summation**: Different weights for surround channels.
4. **Gating**: A two-pass gating system that excludes silence and quiet passages.

Why It Matters for Mastering

Using a non-standard loudness measurement can give you misleading results. Your DAW's built-in loudness meter may or may not conform to BS.1770-4. WhitePrint's analysis engine implements the standard precisely, giving you measurements you can trust.

True Peak vs Sample Peak

BS.1770-4 also specifies true peak measurement, which detects inter-sample peaks that can cause distortion in D/A conversion. This is different from sample peak, which only looks at discrete sample values.