5.3 Accuracy of test equipment

26.1323GPPRelease 18Speech and video telephony terminal acoustic test specificationTS

Unless specified otherwise, the accuracy of measurements made by test equipment shall not exceed the requirements defined in table 1a.

Table 1a: Test equipment measurement accuracy



Electrical Signal Power

± 0,.2 dB for levels ³ -50 dBm

± 0,.4 dB for levels < -50 dBm

Sound pressure

± 0,.7 dB


± 5%


± 0,.2%

Clock (for UE clock accuracy measurement and for any digital electrical reference interface)

±5 PPM

Unless specified otherwise, the accuracy of the signals generated by the test equipment shall exceed the requirements defined in table 1b.

Table 1b: Test equipment signal generation accuracy



Sound pressure level at MRP[, in 1/3rd octave bands]

± 3 dB for 100 Hz to 200 Hz

± 1 dB for 200 Hz to 8 kHz

± 3 dB for 8 kHz to 20 kHz (see note 3)

Mouth simulator equalization

The flatness of the mouth simulator transfer characteristics after equalization, measured in 1/3rd octave bands with the signal used for equalization, shall be within ± 1 dB from 100 Hz to 200 Hz and shall be within ±0.5 dB above 200 Hz (see note 3).

Electrical excitation levels

± 0.4 dB (see note 1)

Frequency generation

± 2% (see note 2)

NOTE 1: Across the whole frequency range.

NOTE 2: When measuring sampled systems, it is advisable to avoid measuring at sub-multiples of the sampling frequency. There is a tolerance of ± 2% on the generated frequencies, which may be used to avoid this problem, except for 4 kHz where only the -2% tolerance may be used.


Not all mouth simulators can be successfully equalized up to 20 kHz; in this case the upper frequency shall be reported. The validity of the equalization, especially with respect to super-wideband and fullband, shall be checked.

The measurements’ results shall be corrected for the measured deviations from the nominal level.

The sound level measurement equipment shall conform to IEC 61672class1 accuracy [38].