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T01020005410701MSWEdoc - ITU-T RECOMMENDATION

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T01020005410701MSWEdoc - ITU-T RECOMMENDATION

    DRAFT REVISED ANNEX E TO RECOMMENDATION P.64

    Definition of handset positions for measuring loudness ratings and frequency

    responses using the P.57 types 3.2 and 3.3 artificial ear on HATS

    Summary

    This Annex describes the handset position to be used when measuring sensitivity/frequency characteristics of local telephone systems using HATS, allowing handsets to be measured using the so-called “ Standard Handset Position “ or offering the possibility to make use of another alternative position for the Type 3.3 ear.

    E.1 Definition of standard handset position for measuring of loudness ratings and

    frequency responses using the P.57 types 3.2 and 3.3 artificial ear on HATS This section describes the handset position to be used when measuring sensitivity/frequency characteristics of local telephone systems using HATS. The HATS position has been shown to be essentially identical to the LRGP position, except for the mouth speaking direction, which has been corrected with a 19 degrees downwards rotation.

    Using Recommendation P.64 terminology, a Cartesian coordinate system with origin in the centre of lips (CL) is introduced. The x axis coincides with the mouth reference axis, and has positive m

    direction into the mouth. The y axis is horizontal, perpendicular to the x axis, with positive mm

    direction towards the right side of the mouth/test head. The z axis is perpendicular to the x and mm

    y axes and with positive direction upwards (refer to Figure E.1). This head-fixed, mouth coordinate m

    system is used. It is parallel to the Frankfurter plane and the HATS reference plane.

    AAzz(up)(up)m: m:

    ECRPECRPxxee

    CCERPERP

    (backw)(backw)xxm: m: CLCLyyeeBByymmCL, Centre ofLipsCL, Centre ofLips

    T1211650-99T1211650-99zzee

    Figure E.1/P.64 Cartesian coordinate systems

    Note: for the standard HATS position ERP and ECRP are coincident.

    - 2 -

    Figure E.1 also shows the ECRP-based Cartesian coordinate system with the axes: x axis: axis of earcap with positive away from the earphone (into the ear). e

     y axis: line of intersection of the handset symmetry plane with the earcap plane. Positive e

    direction towards the microphone.

     z axis: normal to the two other axes. On the right ERP pointing obliquely downwards. e

    The standard HATS position is defined by the following vectors:

    x110.0m((CL-ERP (nominal, right side) y77.9 m((

    ((z40.3m

    x6.0m((EEP-ERP vector (nominal, right side) y11.9m((

    ((z;1.7m

    x0.1932m((y;0.9740x unit vector em((

    ((z0.1184m

    x;0.9088m((y;0.2231y unit vector em((

    ((z;0.3527m

    x0.3699m((y;0.0394z unit vector em((

    ((z;0.9282m

    For the HATS position, the nominal CL-ERP distance is 140.7 mm.

    E.2 Definition of the alternative handset position for measuring of loudness ratings and

    frequency responses using the P.57 3.3 artificial ear on HATS

    This section describes an alternative handset position to be used when measuring sensitivity/frequency characteristics of local telephone systems using HATS. In the case that the

    standard handset position as defined in Section E.1 is found to poorly represent human usage of a

    handset, the alternative position, defined herein, may be defined.

    - 3 -

    The unit vectors defining the coordinate system of the handset and handset positioner are defined in Annex E as x, y and z, Additionally, rotation degrees of freedom, as illustrated in Figure E.1 are eee

    defined as follows:

     Rotational degree of freedom A is defined as a clockwise rotation about the x unit vector e

     Rotational degree of freedom B is defined as a clockwise rotation about the z unit vector e

     Rotational degree of freedom C is defined as a clockwise rotation about the ye unit vector.

    The Manufacturer defined EarCap Reference Point (MECRP) allows for a new point to be defined on the surface of the phone. The MECRP is defined with respect to the ECRP and allows to displacement along the x and y unit vectors only. The pressure force employed to hold the handset ee

    to the HATS will define the position of the handset along the unit vector. Ym

The acceptable range of offset of the MECRP shall not exceed:

     + 10 / - 15 mm along unit vector y e

     ? 10 mm along unit vector z e

The acceptable range of handset rotations about the MECRP shall not exceed:

     ? 6? in rotational degree of freedom A

     ? 6? in rotational degree of freedom B

     ? 5? in rotational degree of freedom C

    Note: In exceptional cases for handsets showing a design where even these ranges for offset and rotation do not allow a close to human use positioning these ranges may be exceeded. Sufficient justification for such deviation shall be given by the manufacturer and/or the test laboratory. The procedure for defining an alternative position is defined as a two step process. Firstly, the handset MECRP is to be defined, allowing an offset along the z and y unit vectors only. In many cases this ee

    will suffice to provide a placement of the handset on the HATS which is similar to human usage. The MECRP may be coincident with the ECRP.

    However, with certain handset form-factors additional angular rotations maybe required to achieve correct placement. Secondly, the angular rotations shall occur about the MECRP. Thirdly the application force is applied by moving the handset in direction Ym

    In order to ensure that the alternative position is unambiguously defined for a given handset type and to ensure that the alternative position can be repeated in any laboratory, the reporting format described in table E.1 shall be used.

    In the standard position, angles A, B and C are defined as the deviation to the unit vectors Ye and Ze from the HATS reference plane and the HATS plane of symmetry. The planes are shown in Figure 1 of ITU-T Recommendation P.58. The values for these angles in the standard position are 21.2?, 13.8? and 2.4? for angles A, B and C, respectively. The adjustment tolerances refer to deviations from the standard position angles.

    - 4 -

    MECRP (delta from actual ECRP)

    Axis Delta [mm]

    y e

    z e

Angle Settings

    Angle Delta from standard angle [?]

    A

    B

    C

     Application Force [N]

Table E.1/P.64 Template structure for reporting the alternative handset position when using the

    ITU-T P.57 3.3 artificial ear on HATS

If the handset manufacturer selects to use either the standard position (as defined in Section E.1) or

    the alternative position (as defined in Section E.2), this uniquely defined position shall be used for

    all measurements associated with this handset type.

    ________________

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