6 Test conditions
26.1323GPPRelease 18Speech and video telephony terminal acoustic test specificationTS
6.1 Environmental conditions
6.1.1 Handset and headset terminals
For handset and headset measurements the test room shall be practically free-field down to a lowest frequency of 275 Hz; the handset or headset, including the HATS, shall be totally within this free-field volume.
Qualification of the test room may be performed using the method and limits for deviation from ideal free-field conditions described in either ISO 3745 Annex A (Table A.2), or ITU-T P. 340 clause 5.4 (Table 1).
Alternatively, a test room may be used which meets the following two criteria:
1. The relationship between the pressure at the mouth opening and that at 5,0 cm, 7,5 cm and 10 cm in front of the centre of the lip ring is within ± 0.5 dB of that which exists in a known acoustic free-field.
2. The relationship between the pressure at the mouth opening and that at the Ear canal Entrance Point (EEP) at both the left and right ears of the HATS does not differ by more than ± 1 dB from that which exists in a known free-field.
The ambient noise level shall be less than -30 dBPa(A); for idle channel noise measurements the ambient noise level shall be less than –64dBPa(A).
Echo measurements shall be conducted in realistic rooms with an ambient noise level ≤ -64 dBPa(A).
6.1.2 Hands-free terminals
Hands-free terminals should generally be tested in their typical environment of application.
For desktop and handheld hands-free terminals the requirements described in clause 5.4 of ITU-T Recommendation P.340 shall be met.
Care must be taken tha noise levels are sufficiently low in order not to interfere with the measurements. The broadband noise level shall not exceed –70 dBPa(A). The octave band noise level shall not exceed the values specified in Table 2.
Table 2: ITU-T P.340 Noise levels
|
Center frequency |
Octave band pressure level |
|
63 |
–45 |
|
125 |
–60 |
|
250 |
–65 |
|
500 |
–65 |
|
1 000 |
–65 |
|
2 000 |
–65 |
|
4 000 |
–65 |
|
8 000 |
–65 |
Echo measurements shall be conducted in realistic rooms with an ambient noise level ≤ -70 dBPa(A).
6.2 System simulator conditions
Unless otherwise specified for the respective test, the system simulator should provide an error-free radio connection to the UE under test. The speech codec and bitrate shall be as defined in clause 5. Discontinuous Transmission (DTX) silence suppression shall be disabled in uplink and downlink for the purposes of GSM acoustic testing by appropriate configuration of the system simulator. For 3G, LTE, NR and WLAN, DTX shall be disabled for the downlink path by appropriate configuration of the system simulator, unless otherwise stated for the respective test. If DTX is enabled for the downlink path in a respective test using the EVS codec, the system simulator shall use DTX/CNG operation for EVS Primary with a SID update rate of once every 8 frames as described in clause 4.4.3 of TS 26.445.
NOTE: For LTE/NR/WLAN with AMR and AMR-WB codecs and for 3G, the UE DTX for the uplink path cannot be controlled from the system simulator.