Loudness

The loudness is one of Stanley Smith Stevens (1936) and defined by standards size disproportionate to the figure of the human loudness perception. The unit of loudness is the sone sone with the unit symbol.

The sone is defined as the perceived volume of a sound event. 1 sone corresponds to a volume level of 40 phon; that is, a broadband noise which is perceived as loud, like a sine wave with a sound pressure level of 40 dB SPL ( Sound Pressure Level engl. ) at a frequency of 1 kHz.

The loudness is doubled when the sound is perceived as twice as loud. Loudness is a psycho-acoustic term that describes how a number of subjects the perceived loudness of sound examined primarily. This psychoacoustic results can be put together with physical and medical conditions in relation.

For a sine wave of frequency 1 kHz to increase the volume by 10 phon leads to a doubling of the loudness. This relationship corresponds to the Stevens 's power law, however, applies only for medium and high volume levels from 40 phon. At lower volume levels already leads a smaller volume increase than 10 dB to the feeling of doubling of loudness.

The loudness of a sound affects the performance of its temporal and spectral structure.

The loudness depends on the sound pressure level, the frequency spectrum and the timing of the sound. Is caused loudness perception of the way the sound processing in the inner ear. There, the sonic vibrations are converted into nerve impulses. Depending on the strength of the excitation of nerve cells a sound is judged louder or quieter.

There are models that - based on the inner ear mechanics - can describe the sense of volume of people (modeling of masking effects). For some time, technical devices are available that simulate the sense of volume of people and thereby can measure. Result here is the loudness in sone. The standardized measurement method for loudness measurement can be found in DIN 45631 and ISO 532 B.

In measurement practice this method, however, continue to play a most subordinate role. In the noise measurement and assessment predominantly weighted sound pressure levels are used instead of the loudness. Mostly the A-weighting is used alone, sometimes the C-weighting, while the weighting filters B and D are used only rarely. These sound pressure levels are the different sensitivity of the ear for various frequencies reproduce. The level-dependent frequency dependence of the noise perceived to be modeled on the different weighting filters, the occlusion remains unconsidered. Other psychoacoustic parameters are not acquired with.

The course of the A-weighting approximately corresponds to the frequency response of the ear at low sound pressure levels by about 30 dB and reduces in comparison to other weighting filters high and low frequency noise components from strong. It should be noted also that the A-weighting ( such as volume and loudness) is based only on pure sine tones and can not be directly transferred to more complex sounds.

Since such a simple level measurement, the loudness or even the noise impact with their annoyance can not adequately express surcharges are in the assessment of noise emissions still often awarded to help offset the errors of the weighted level measurement, such as surcharges for tonal components, impulsiveness. An assessment level is then formed from the measured value and the aggregates. There are different methods to loudness calculations.