GENESIS provides a free download of the "Loudness Toolbox" allowing the calculation of loudness with respect to the models described below. This toolbox has been developed for Matlab(R). An .exe version and the corresponding source codes will be provided in the future.
What is loudness ?
Loudness is a subjective quantity corresponding to the perceived sound level. It is closely linked to the sound level but also to the frequency and the duration of the sound. Loudness is measured in sone, a unit based on a sensory scale. This scale has been built from psychoacoustics measurement methods called direct measures (Stevens, 1956).
This type of experiment is based on the following procedure: during an experiment, people are presented several sounds (with different frequencies and intensities), and are asked to give a figure proportional to the loudness of each sound.
Loudness modelsIn order to estimate loudness without using a psychoacoustic test, several models are proposed in scientific literature.
For steady-state sounds (stationary), two calculation methods are standard references - Zwicker's model (1958) and Moore's model (1996). Zwicker's model is in the german national standard DIN45631 (1991) and in the ISO532B International Standard . Moore's method led to the American Standard ANSI S3.4-2007 (2007).
Concerning non stationary sounds (i.e. which characteristics vary with time), two main models have been developed. The first one was published by Zwicker et Fastl (1999) and the second one by Glasberg et Moore (2002). An international standardisation is currently under discussion. Note that the german national standard DIN45631/A1(2008) is an addendum that concerns the calculation of loudness versus time.
Boullet (2006) conducted research on the loudness of impulsive sounds- i.e sounds which waveform is characterised by a fast transient phase, no steady phase, and a more or less long decay phase depending on the sound. The LMIS (Loudness Model for Impulsive Sounds) was developed to estimate the global loudness of similar sounds.
Loudness calculations implemented in the toolbox
The following table sums up the models implemented in the toolbox and their respective application domain:
|ISO 532B / DIN 45631 (Zwicker et al)|
|ANSI S3.4-2007 (Moore et al)|
|Zwicker for temporally variable sounds|
|Moore et al for Time-Varying Sounds|
|Boullet - Loudness Model for Impulsive Sounds|
The Loudness toolbox is provided as a ZIP compressed archive (Loudness_Toolbox.zip), containing the following files:
- Loudness_Indicators.pdf : document detailing the loudness models in the toolbox and giving the bibliographical references used to develop the toolbox,
- UsersGuide_Loudness_toolbox.pdf : users guide containing the installation and using procedures,
- *.m files : all the necessary Matlab functions and subfunctions allowing the loudness computations according to the models listed in the table above,
- a set of WAV files (synthetic and from the real-world) used to validate the calculations,
- readme.txt: document giving information and using conditions,
- changes.txt: log file of toolbox evolutions.
The Loudness toolbox for Matlab is compatible with any operating system that has Matlab installed with a Signal Processing toolbox.
For any comments or suggestions, please contact Genesis' support at firstname.lastname@example.org
GENESIS would like to thank all the people and partners who helped in building and developping this Loudness Toolbox project.
In particular, special thanks to:
- Acoustics and Mechanics Laboratory (Laboratoire de Mécanique et d'Acoustique - LMA - UPR-7051), CNRS, Marseille
- Sabine Meunier, Guy Rabau, Isabelle Boullet
- French Environment Ministry (Ministère de l'Aménagement du Territoire et de l'Environnement, MATE) for the funding through the PREDIT project (2005-2007)
- Christophe Couvreur for the third octave levels Matlab function
The calculations of loudness and other psychoacoustics indicators are implemented in the LEA Software by GENESIS.