ISO 532-1-2017 pdf free.Acoustics一Methods for calculating loudness一Part 1:Zwicker method.
Then, for each band a slope towards the higher critical band is 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 j 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-third-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 next 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 Figure 2.
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 pattern”, 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. to the total area below the curve. Therefore, it contributes especially to the total loudness of pure tones. An example is given in Figure 2 by the dotted line for a 1 kHz tone with a sound pressure level of 70 dB. Generally, one-third-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 dli produces the following levels at different centre frequencies: 50dB at 800 Hz, 70 dB at I kHz and 50 dli 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 this 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 level 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 LN.D 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 68 dB on the one hand, and the calculated loudness level of 86 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 clearly 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 Figure 2 for example, the one-third-octave-band level of 51 dli 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-thirdoctave-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.ISO 532-1 pdf free download.