Content for TS 26.131 Word version: 18.1.0

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7.5 Sidetone characteristics (handset, headset, and analogue electrical interface UE) 7.5.1 Sidetone loss 7.5.2 Sidetone delay 7.6 Stability loss 7.7 Echo control 7.7.1 General 7.7.2 Acoustic echo control in desktop hands-free UE 7.7.3 Acoustic echo control in hand-held hands-free UE 7.7.4 Acoustic echo control in a handset UE 7.7.5 Acoustic echo control in a headset UE 7.7.6 Echo control in an electrical interface UE
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7.5 Sidetone characteristics (handset, headset, and analogue electrical interface UE) p. 77

7.5.1 Sidetone loss p. 77

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.

7.5.2 Sidetone delay p. 77

The maximum sidetone delay shall be ≤ 5 ms, measured in an echo-free setup.

Compliance shall be checked by the relevant test described in TS 26.132.

7.6 Stability loss p. 77

The stability loss presented to the PSTN by the 3G, LTE, NR or WLAN network at the POI should meet the principles of the requirements in clauses 2 and 3 of ITU-T Recommendation G.122 [6]. These requirements will be met if the attenuation between the digital input and digital output at the POI is ≥ 6 dB at all frequencies in the range 100 Hz to 16 kHz under the worst case acoustic conditions at the UE (any acoustic echo control should be enabled). For the normal case of digital connection between the Air Interface and the POI, the stability requirement can be applied at the Air Interface.

The worst case acoustic conditions will be as follows (with volume control set to maximum for each following condition):

Handset UE:

the handset lying on, and the transducers facing, a hard surface with the ear-piece uncapped;

Headset UE:

for further study;

Hands-free UE:

no requirement other than echo loss.

7.7 Echo control p. 78

7.7.1 General p. 78

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.

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.

7.7.2 Acoustic echo control in desktop hands-free UE p. 78

The TCLw for the desktop and vehicle-mounted hands-free UE shall be ≥ 40 dB for any setting of the volume control.

The TCLw for the desktop hands-free and vehicle-mounted 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.

7.7.3 Acoustic echo control in hand-held hands-free UE p. 78

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.

7.7.4 Acoustic echo control in a handset UE p. 78

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.

With the volume control set to maximum TCLw should be ≥55 dB.

It is recommended that the volume control should be set back to nominal after each call unless TCLw ≥ 55 dB can also be maintained with the maximum volume setting.

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.

7.7.5 Acoustic echo control in a headset UE p. 79

The TCLw for headset UE shall be ≥ 46 dB for any setting of the volume control.

The TCLw for headset UE shall be ≥ 55 dB at the nominal setting of the volume control.

The volume control shall be set back to nominal after each call unless a TCLw ≥ 55 dB can also be maintained with the maximum volume setting.

Due to the obstacle effect of the head in this type of terminal, careful design might mean that no active echo control is necessary.

The echo cancellation algorithm 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.

7.7.6 Echo control in an electrical interface UE |R17| p. 79

The TCLw for electrical interface UE shall be ≥ 46 dB for any setting of the volume control.

The TCLw for electrical interface UE shall be ≥ 55 dB at the nominal setting of the volume control.

The volume control shall be set back to nominal after each call unless a TCLw ≥ 55 dB can also be maintained with the maximum volume setting.

The echo cancellation algorithm 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.