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Loudness is a psychoacoustic quantity that describes how a number of test persons predominantly assess the perceived loudness of sound . It serves for the proportional representation of the human volume perception: If the sound is perceived as twice as loud, the loudness doubles.

Loudness is defined by standards ( measurement method in DIN 45631 and ISO 532 B) and was first defined in 1936 by Stanley Smith Stevens .

Definition and unit of measure

Relationship between Sone and Phon

The unit of measurement for loudness is the sone with the symbol sone . The sone is defined as the perceived volume of a sound event . 1 sone corresponds to a volume level of 40  phons , i.e. H. a wide-band sound that is perceived as loud as a sinusoidal tone of frequency 1 kHz with a sound pressure level of 40 dB SPL (English Sound Pressure Level ).

With a sinus tone with a frequency of 1 kHz, an increase in volume by 10 phons leads to a doubling of the loudness. This relationship corresponds to Stevens' power law , but only applies to medium and high volume levels from 40 phon. At lower volumes, a volume increase of less than 10 dB leads to the feeling of doubling the loudness (see illustration).

The loudness depends on the sound pressure level, the frequency spectrum and the time behavior of the sound.

There are different methods of loudness calculations . See also → main article: Loudness calculation according to Zwicker and Stevens

root cause

The perception of loudness is caused by the way sound is processed in the inner ear . There the sound vibrations are converted into nerve impulses . Depending on the strength of the excitation of the nerve cells , a noise is judged louder or quieter.

The loudness of a sound also influences the perception of its temporal and spectral structure.

There are models that - based on the inner ear mechanics - can describe the volume perception of humans (modeling of masking effects ). For some time now, technical devices have been available that simulate human volume perception and thereby measure it. The result here is the loudness in sone .

Loudness compared to the weighted sound pressure level

Weighting filters A, B, C, D and sensitivity of hearing

In the noise measurement and evaluation will take the loudness mostly sound pressure level mostly alone the A: used Rating B- and D-evaluation, sometimes the C-weighting, only rarely. The weighted sound pressure levels are intended to simulate the different sensitivity of the hearing for different frequencies, but the masking and other psychoacoustic parameters are not taken into account.

The course of the A-weighting corresponds roughly to the frequency response of the hearing at low sound pressure levels by about 30 dB and, compared to other weighting filters, greatly reduces high and low-frequency noise components . The A-weighting (like volume and loudness) is based on pure sine tones and cannot be directly transferred to more complex noises.

Since such a simple level measurement cannot adequately express the loudness or even the noise effect with its annoyance , surcharges are often given when assessing noise emissions , which are intended to compensate for the errors of the assessed level measurement, e.g. B. Surcharges for tonality or for impulsiveness . An assessment level is then formed from the measured value and the surcharges .

Web links

Commons : Loudness  - collection of images, videos and audio files
Wiktionary: loudness  - explanations of meanings, word origins, synonyms, translations