LUFS Loudness Calculator

How to Measure and Match LUFS Loudness

The International Loudness Revolution: ITU-R BS.1770 and the Death of the Loudness War

For decades, the commercial music industry was locked in the destructive "Loudness War." Record labels used extreme brickwall limiters and multi-band compression to crush dynamic range, driving music as loud as $-6 ext{ LUFS}$ to stand out on FM radio. The consequence was severe ear fatigue, lost musical punch, and audible clipping distortion.

The International Telecommunication Union solved this problem by defining ITU-R BS.1770, creating the LUFS (Loudness Units Full Scale) or LKFS metric. Unlike simplistic peak or RMS meters, LUFS incorporates human ear acoustic modeling:

1. The K-Weighting Acoustic Filter

The human auditory system is not equally sensitive to all frequencies. The K-weighting curve applies two stages of digital filtering:

• Stage 1 (High-Frequency Head Simulation): A high shelving filter boosting frequencies above $1.5 ext{ kHz}$ by $+4 ext{ dB}$ to simulate acoustic diffraction around the human skull.
• Stage 2 (Low-Frequency Roll-off): A 2nd-order high-pass filter at $100 ext{ Hz}$ modeling the human ear's relative insensitivity to deep sub-bass rumble (the Fletcher-Munson equal-loudness contour).

2. Gated Loudness Integration

To prevent quiet intro passages or speech pauses from falsely skewing the measurement down, BS.1770 applies a two-stage gating threshold: an absolute gate at $-70 ext{ LKFS}$, followed by a relative gate $10 ext{ LU}$ below the ungated mean. Only energetic musical passages are integrated into the final number.

Key Benefits of the LUFS Loudness Calculator

Frequently Asked Questions