Loudness calculation
The loudness calculation is a method for the computational determination of the psychoacoustically perceived loudness .
The calculation of the loudness or the loudness level of a sound from its objectively measurable data such as sound level , spectrum , time function is a complex process because many properties of the human hearing must be taken into account.
With simple procedures, the result will only in rare cases exactly match the mean value of the subjectively found results. For two somewhat more complex calculation methods, which are briefly described below, however, an accuracy can be achieved that corresponds to that of the subjective measurements. Both methods are standardized for uniform, quasi-stationary sounds.
- The Stanley Smith Stevens method is mostly used when octave filters are used as spectrum analyzers (individual values: octave level). An attempt is made to determine the mutual influence of the partial loudnesses with the help of a formula and auxiliary diagrams.
- The method according to Eberhard Zwicker uses third- octave filters as an approximation for the frequency groups (individual values : third-octave level). Then work with 10 templates that apply to certain third octave level ranges or to the sound field shapes, flat or diffuse. The measured third octave levels are entered into these templates and further processed graphically using the principle that partial areas correspond to partial loudnesses and the total area corresponds to the overall loudness. This creates a clear picture for the user. Optionally, a computer program takes over the graphic evaluation, which further simplifies the application of the method.
With both methods, the loudness of the sound is first determined as the measure that is proportional to the intensity of the sensation . The associated loudness level is then obtained from the loudness via the relationship specified in DIN 45631 (see literature).
Sound level meters measure in contrast, only the physical level of a sound, by weighting filter frequency dependent weighting can be. There are also measuring devices available that can also perform the loudness calculation according to Zwicker.
literature
- ISO 532, Acoustics-Method for Calculating Loudness Level.
- DIN 45631, calculation of the volume level from the noise spectrum. Method according to Eberhard Zwicker.
- ANSI S3.4-2007 American National Standard Procedure for the Computation of Loudness of Steady Sounds. Method according to Brian R. Glasberg, Brian CJ Moore: Prediction of absolute thresholds and equal-loudness contours using a modified loudness model. In: The Journal of the Acoustical Society of America. Vol. 120, No. 2, 2006, ISSN 0001-4966 , pp. 585-588, doi : 10.1121 / 1.2214151 .