BRUEL & KJAER 4128-C - Chapter 7 Specifications

CHAPTER 4
Type 4606 Features and Functions
51
4.3.4 Position
 B and  C are recorded to the nearest ½ using the markings provided on the swivel joints.
 A is measured off the end of the slide on the mounting bracket.
4.3.5 Standardised Measurements
Type 4606 is easy to set up for standardised measurements according to ITU-T Rec. P.64 (11/
2007). The following descriptions are valid for HATS mounted with Artificial Ear ITU-T Rec.
P.57 Type 3.3 (Brüel &Kjær Types 4158-C and 4159-C).
Positioning Terminology
A Cartesian coordinate system is used to describe the standardised position by means of
vectors. Using ITU-T Rec. P.64 terminology, the coordinate system originates at CL and
consists of three axes called x
m
, y
m
and z
m
. The x
m
-axis has positive direction into the mouth
and coincides thereby with the mouth reference axis. The y
m
-axis is horizontal, perpendicular
to the x
m
-axis with positive direction towards the right side of the head and the z
m
-axis is
perpendicular to the x
m
-axis and y
m
-axis with positive direction upwards. This head-fixed
coordinate system corresponds to the HATS reference plane (see Fig.4.12).
Fig.4.12
Diagram of vector
directions for head fixed
coordinate system
Similar to the head-fixed coordinate system, a Cartesian coordinate system must be defined for
the telephone handset. This coordinate system originates from the handset ECRP and defines
three axes: x
e
-axis is normal to the ear-cap plane with positive direction away from the
earphone. The y
e
-axis is the line of intersection of the handset symmetry plane with positive
direction towards the microphone. The z
e
-axis is normal to the other two axes and is for
handsets applied to the right ear. The z
e
-axis points obliquely downwards.
With these two coordinate systems in mind, the standardised positions as defined in ITU-T
Rec. P.64 can be set up as described in the following.
Refer to ITU-T Rec. P.64 for the exact vector definitions of the standardised positions.
980409/1
z
e
y
e
x
e
y
m
x
m
(backw)
z
m
(up)
ECRP
CL
ECRP, Ear-cap Reference Point
CL, Centre of Lips
B
C
A