Loudness Measurement Tool

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This Windows app promotes management of audio program loudness in production and Internet streaming.  It can measure audio files at approximately 30X speed and play most Internet audio streams, using any of the leading audio codecs.  The software tool is based on International Telecommunications Union Recommendation BS.1770-3 using libraries from the FFmpeg project under the LGPLv2.1.
For Internet audio streams and files, the tool provides:

  • Integrated Loudness measurements in-progress
    • For streams, accurate measurements may require from 3 to 30 minutes, depending on the variation in loudness;
    • The European Broadcast Union Recommendation 128 prescribes a target of -23 LUFS for audio production and transmission.
  • True Peak measurements based on oversampling
    • Predictive reconstruction of peaks estimate peaks that may have exceeded full-scale before encoding;
    • Note that this may result in peaks being displayed with a positive dBTP value!
  • ITU Loudness Range
    • Measure of loudness variation over any sample interval (the longer the better);
    • Smaller values suggest less need for further dynamic processing of the audio.
  • High-fidelity decoded audio playback by checking on “Enable Audio”
    • Most codecs supported;
    • As measurement is coupled to decoding, calibration of level is intrinsic to the application.
  • Real time audio visualization by checking on “Enable Visualization”
    • Displays an amplitude and frequency ‘waterfall’ or
    • Triggered waveform oscilloscope;
    • Press the “w” key to toggle between each.
  • Display of playback duration or running time of files in high-speed measurement (with Enable Audio unchecked).
  • Test audio files and stream, toggled by clicking on the “npr” logo
    • A 1 kHz @ -20 dBFS, 16-bit @ 48 kHz, 48 kb/s HE-AAC, reference tone;
    • A sample of NPR programming, 16-bit @ 44.1 kHz, 48 kb/s HE-AAC, normalized to -23 LUFS;
    • NPR Labs’ test stream, 48 kb/s HE-AAC, SBR, no parametric stereo.


No installation is required

  • Note that the two FFmpeg support files must be kept in the same path at the Loudness Measurement Tool application;
  • App requires Microsoft .NET Framework v4.0 or newer.
  • Unzip files to any convenient location (but avoid very long path names).


Click here to download the .zip file