Isosonic curves
A isosonic curve is a measurement of the sound pressure (in Décibel S), according to the frequency, that a person perceives like a of the same sound level. The measuring unit of level of its is the phon . Two sinusoidal waves of equal phon have, by definition, the same noise level.
The human auditive system is sensitive to frequencies going of 20 Hz with a maximum from approximately 20.000 Hz. But the audio extent of frequencies decreases with the old due one to the Presbyacousie. In this frequency band, the human ear is most sensitive between 1 and 5 Khz. This is due mainly to the resonance of the auditive channel and the transfer transfer function of the Osselets in the internal ear.
The isosonic curves were measured for the first time in 1933 by Fletcher and Munson. In their study, one made hear on the subjects of the pure sounds (sinusoidal) at various frequencies and by increments of 10 dB. One made also hear on the subjects a sound of reference to 1000 Hz. One adjusted the volume of the latter sound until it is perceived on the same noise level as that in test. As the sound feeling of volume is very subjective and difficult to measure, Fletcher and Munson used the average of measurements on much of subjects to obtain reasonable averages.
In 1956 Robinson and Dadson took the new measurements, considered as more precise. Those were the base of the standard ISO226 which was regarded as final until 2003.
Because of divergences between old measurements and recent the International organization of standardization (ISO) brought up to date, in 2003 the standard ISO 226, while basing itself on several studies of researchers Japanese, German, Danish, British and North-American. The new standard is the ISO226: 2003 (image of right-hand side).
| Random links: | Time serieses | Isidor Straus | Machines of the athletics | Chronology of the Khmer Empire | Drâa | Chang-Rae_Lee |