Content for  TS 26.131  Word version:  18.1.0

The talker sidetone masking rating (STMR) shall be ≥ 15 dB and should be ≤ 23 dB for the nominal setting of the volume control. For all other positions of the volume control, the STMR shall be ≥ 10 dB. In case the STMR is below the lower limit also when the electrical sidetone path has been disabled, the result shall not be regarded as a failure. Compliance shall be checked by the relevant test described in TS 26.132. The bandwidth for the sidetone path provided by the UE may in some terminals not be restricted to the narrowband range. In case the sidetone path operates in a mode other than narrowband (to be declared by the manufacturer), compliance shall be checked using the test described for "Wideband telephony transmission performance".

The maximum sidetone delay should be ≤ 5 ms, measured in an echo-free setup. Compliance shall be checked by the relevant test described in TS 26.132.

The echo loss (EL) presented by the 3G, LTE, NR or WLAN network at the POI should be sufficient during single-talk. This takes into account the fact that the UE is likely to be used in connections with high transmission delay and in a wide range of noise environments. See ITU-T Recommendation G.131 for general guidance. The use of acoustic echo control is not mandated for 3G, LTE, NR or WLAN networks and the connection between the UE and the POI is zero loss. Therefore the acoustic echo control provided in the UE should provide a sufficient TCLw at the POI over the likely range of acoustic end delays. If acoustic echo control is provided by voice switching, comfort noise should be injected. This comfort noise shall operate in the same way as that used in DTX.

The TCLw for the desktop hands-free UE shall be ≥ 40 dB for any setting of the volume control. The TCLw for the desktop hands-free UE shall be ≥ 46 dB when measured under free-field conditions at the nominal setting of the volume control. The echo canceller should be designed to cope with the expected reverberation and dispersion. In the case of the hands-free UE, this reverberation and dispersion may be time variant. Compliance with this requirement shall be checked by the relevant test described in TS 26.132.

The TCLw for hand-held hands-free UE shall be ≥ 40 dB for any setting of the volume control. The TCLw for hand-held hands-free UE shall be ≥ 46 dB at the nominal setting of the volume control. The echo canceller should be designed to cope with the expected reverberation and dispersion. In the case of the hands-free UE, this reverberation and dispersion may be time variant. Compliance with this requirement shall be checked by the relevant test described in TS 26.132.

The TCLw for handset UE shall be ≥ 46 dB for any setting of the volume control. The TCLw for handset UE should be ≥ 55 dB at the nominal setting of the volume control. The echo canceller should be capable of dealing with the variations in handset positions when in normal use. The implications of this are under study. Compliance with this requirement shall be checked by the relevant test described in TS 26.132.

The TCLw for headset UE shall be ≥ 46 dB for any setting of the volume control. The TCLw for headset UE should be ≥ 55 dB at the nominal setting of the volume control. The echo canceller should be designed to cope with the expected reverberation and dispersion. Compliance with this requirement shall be checked by the relevant test described in TS 26.132.

The TCLw for electrical interface UE shall be ≥ 46 dB for any setting of the volume control. The TCLw for electrical interface UE should be ≥ 55 dB at the nominal setting of the volume control. The echo canceller should be designed to cope with the expected reverberation and dispersion. Compliance with this requirement shall be checked by the relevant test described in TS 26.132.