ContentDepot: NPR Loudness Tool

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The NPR® Loudness Tool (NLT) checks the levels of an audio file or files and indicates if they meet Public Radio Satellite System® (PRSS®) submission standards. The NLT provides the option to adjust levels such that the resulting file is within the PRSS specifications.  Specifically, it adjusts the Integrated Loudness and the True Peaks, then saves the adjusted file.  You can install the NLT on your Mac or PC to check the levels of your audio files.

Click here to download the tool for a PC. (.zip)

Click here to download the tool for a MAC (


NPR Loudness Tool (to check and adjust the loudness levels of audio files)
Copyright © 2016 NPR
This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.  In addition, the names of NPR, NPR Labs, and the PRSS may not be used for publicity purposes to endorse or promote products based on this program without express prior written permission.
This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details: .
Source code for the NPR Loudness Tool is available at
FFmpeg library
Copyright © 2012 Clément Bœsch
The NPR Loudness Tool uses the f_ebur128.c library, which is code of FFmpeg,, licensed under the GPL 3 or later,, and its source can be downloaded here:  

NPR does not own this code.


For PC users:
Click here to download instructions. (PDF)

For Mac users:
Click here to download instructions. (PDF)


If you have any questions on how to use this application, please contact the PRSS Help Desk at, or at 800.971.7677.