ISO 532-1:2017 pdf free download.Acoustics-Methods for calculating loudness Part 1 : Zwicker method.
Loudness and loudness level are two perceptual attributes of sound. describing absolute and relative sensations of sound strength perceived by a person under specific listening conditions. Due to inherent individual differences among people, both loudness and loudness level have the nature or statistical estimators characterized by their respective measures of central tendency and dispersion determined for a specific sample of the general population.
The object of the ISO 532 series is to specify calculation procedures based on physical properties of sound for estimating loudness and loudness level of sound as perceived by persons with otologically normal hearing under specific listening conditions. Each procedure provides single numbers that can he used in many scientific and technical applications to estimate the perceived loudness and loudness level of sound, without conducting separate human observer studies for each application. Because loudness is a perceived quantity, the perception of which may vary among people, any calculated loudness value represents only an estimate of the average loudness as perceived by a group of individuals with otologically normal hearing.
ISO 532.1 and ISO 532.2 specify two different methods for calculating loudness which may yield different results for given sounds, Since no general preference for one or the other method can presently be stated, it is up to the user to select the method which appears most appropriate for the given situation. Some major features of each of the methods are described below to facilitate the choice.
The first method of ISO 532-1 describes the calculation of loudness and loudness level of stationary sounds and is based on DIN 45631:1991. The second method olthis document covers the procedures for calculation of loudness and loudness level of arbitrary non-stationary (time-varying) sounds, including stationary sounds as a special case, and is based on DIN 45631/A1;2010.
This document also includes a program code for both methods leading to estimates of loudness and loudness level for stationary and time-varying sounds. An executabLe computer program is also provided for both methods. The applied software is normative for calculating loudness values, against which other implementations can be checked subject to stated tolerances, and provides additional functionality for the convenience of the user.
The method for stationary sounds In ISO 532-1 differs slightly from the methods included In the previous ISO 532:1975, method B, by specifying corrections for low frequencies and by restricting the description of the approach to numerical instructions only, thus allowing a unique software description. For reasons of continuity, the method given in tins document is in accordance with ISO 226:1987 instead of the later revised version, ISO 2262OO3.
Based on the general concept of the method for stationary sounds, the method for time-varying sounds incorporates a generalization of the Zwicker approach to arbitrary, non-stationary sounds. Of course, this generalization Is compatible with the method for stationary sounds in that It gives the same loudness values as the method for stationary sounds if applied to stationary sounds.
The Moore-Glasherg method as Implemented In ISO 532-2 Is limited to stationary sounds and can be applied to tones, broadband noises and complex sounds with sharp line spectral components. The method in ISO 532-2 dIffers from those in ISO 532:1975. ISO 532:1975. method A (Stevens loudness). was removed as this method was not often used and its predictions were not accurate for sounds with strong tonal corn ponents. The method described in ISO S2-2 also improves the precision of calculated loudness in the low frequency range and allows for calculation of loudness under conditions where the sound differs at the two ears. it has been shown that this method provides a good match to the contours of equal loudness level as defined in ISO 226:2003 and the reference threshold of hearing as defined in
ISO 389-7:2005.
NOTE Equipment or machinery noise emissionsfimmissions can also be pudged by other quantities defined in various International Standards (see e.g. ISO 1996-1. 150 3740,1509612 and ISO 11200).
Then, for each band a slope towards the higher critical band 15 added, and the area below the distribution of specific loudness is summed. The specific value of the slope to be added depends on the respective one-third-octave-band levels and centre frequencies. Again, detailed information can be found In the above mentioned graphical representations or In the tables of A.3. respectively. Having entered the corrected one-thIrd-octave-band levels Into the diagram, the shape of the specific loudness pattern starts with a vertical rise to the one-thlrd•octave.band level measured, stays at the main value corresponding to the one-third•octave-band level In question and then falls with a slope unless the level is higher in the ncxt one-third.octave band, in which case the pattern rises vertically to the level appropriate for the next one-third-octave band. Both the one-third-octave-band spectrum and the loudness pattern are highlighted by solid curves in the diagram of Figure2.
If the next one-third-octave-band level is lower, the decrease of the specific loudness towards higher centre Frequencies follows the broken lines, corresponding to the upper slope. In this way, the final specific loudness versus critical band rate pattern, shortened to loudness patter&, Is determined and Indicated by the highest thick solid lines In FIgure 2. For narrow.band sounds, this upper slope contributes strongly to the total loudness, i.e. Lu the total area below the curve. Therefore, It contributes especially to the total loudness of pure tones. An example is given In Eigure2 by the dotted line for a 1 kHz tone with a sound pressure level of 70 dB, Generally, one-thlrd.octave-band filters show a leakage towards neighbouring filters of about -20 dB. This means that a 1 kHz tone with a sound pressure level of 70 dB produces the following levels at different centre frequencies: SO dB at 800 Hz, 70dB at 1 kHz and 50dB at 1,25 kHz, Therefore, the lower slope of the loudness pattern becomes less steep.
The solid curve in FIgure 2 shows the loudness pattern of a factory noise. An area is formed extending from low to high frequencies. It Is bordered by the straight line upwards at the left and right sides of the overall diagram, and also by the horizontal lower abscissa. The area within these boundaries Is marked by hatching. To calculate the area quantitatively, a rectangular surface of equal area Is drawn, which has the width of the diagram as a basis. The height of thfs rectangle is a measure of the total area, which is marked by shading from upper left to lower right. Using this height (the dashed-dotted line), the loudness or the loudness ‘evel can be read from the scales on the right or the left of the diagram. In the diffuse field example shown in Figure 2, a calculated loudness ND of 24 sone and a corresponding loudness level LMO of 86 phon is found. The sound under test has a relatively broad spectrum. Therefore there is quite a large difference between the measured sound pressure level of 73 dB or the A-weighted sound pressure level of 68dB on the one hand, and the calculated loudness level o186 phon on the other hand.
The graphical procedure which finally leads to a loudness pattern has the advantage that partial areas In the diagram correspond to specific parts of the loudness, Therefore, in many cases the diagram dearly shows which partial area is dominant or which part contributes strongly to the total loudness. In many applications it is often very important to first reduce that part of the noise which produces the largest area in the loudness pattern. On the other hand, the diagram shows which parts of the spectrum are so small in relation to the neighbouring parts that they are partially or even totally masked. In Figure2, for example. the one-third-octave-band level of 51 dB at the centre frequency of 630 Hz does not contribute to loudness because it is totally masked, as indicated by the fact that this one-third- octave-band level lies below the shaded curve limiting the total area and arising, at this frequency, from the one-third-octave-band level at 500 HZ.