ISO 11904-2:2021 pdf download.Acoustics一Determination of sound immission from sound sources placed close to the ear
1 Scope
This document specifies basic framework measurement methods for sound immission from sound sources placed close to the ear. These measurements are carried out with a manikin, equipped with ear simulators including microphones. The measured values are subsequently converted into corresponding free-field or diffuse-field levels. The results are given as free-field related or diffuse-field related equivalent continuous A-weighted sound pressure levels. The technique is denoted the manikin technique.
This document is applicable to exposure to sound from sources close to the ear, for example during equipment tests or at the workplace to sound from earphones or hearing protectors with audio communication facilities.
This document is applicable in the frequency range from 20 Hz to 10 kHz. For frequencies above 10 kHz,ISO 11904-1 can be used.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
IEC 61260, Electroacoustics一Octave-band and fractional-octave-band filters
IEC 61672-1, Electroacoustics一Sound level meters一Part 1: Specifications
ITU-T P.58:2013, Head and torso simulator for telephonometry
3.2 free-field frequency response for use with manikins
average human free-field frequency response for use with manikins, corrected for the difference between the sound transmission inside the average human ear canal and the corresponding transmission of the manikin ear simulator
Note 1 to entry: For applicability with manikins, the eardrum reference is replaced by the output of the manikin ear simulator in tabulated values of OLFF,M,f
Note 2 to entry: The free-field frequency response for use with manikins is identical to the amplitude of the head-related transfer function (HRTF) for frontal sound incidence.
Note 3 to entry: The human free-field frequency response is defined in ISO 11904-1.
3.3 diffuse-field frequency response for use with manikins
average human diffuse-field frequency response for use with manikins, corrected for the difference between the sound transmission inside the average human ear canal and the corresponding transmission of the manikin ear simulator
Note 1 to entry: For applicability with manikins, the eardrum reference is replaced by the output of the manikin ear simulator in tabulated values of OLDF,M,f
Note 2 to entry: The human diffuse-field frequency response is defined in ISO 11904-1.
3.4 free-field related sound pressure level determined with a manikin
free-field sound pressure level determined with the method using a manikin
Note 1 to entry: The definition may be applied to specific frequencies or frequency bands, weighted or unweighted levels, specific time weightings, etc., for instance "free-field related equivalent continuous A-weighted sound pressure level" (free-field related LM,Aeq' also denoted LFF,M,Aeq).
Note 2 to entry: The method is aimed at the mean free-field related sound pressure level that would be obtained with a large human population.
Note 3 to entry: The free-field related sound pressure level for a human subject is defined in ISO 11904-1.ISO 11904-2 pdf download.