Tone Levels; Codecs - Avaya Application Solutions Deployment Manual

and cross-talk effects. In principle, the transmit loss of telephones could be made very large
followed by signal amplification in the receiving telephone. In practice however, the transmit loss
should be limited to prevent the electrical voice signal from dropping below electrical
background noise. This has resulted in the adoption of transmit loss and receive loss values
around 8 dB and 2 dB, respectively, although country-specific values may actually deviate quite
significantly from these values.
The loss plan administration provided by Avaya Communication Manager software is primarily
intended to control signal losses in telephones and gateways, and not to control echo. However,
in case of severe echo, the administered loss can be changed to a different plan. In principle, an
increase of the loss between two endpoints by a certain amount will increase the echo loss by
twice this amount. In general, it is not advised to use loss plan administration in this way without
consultation with Avaya Services personnel. It is better to reduce the echo by strategic
deployment of echo cancelers.

Tone Levels

The level of call progress and DTMF tones played out through telephones must also adhere to
specified levels in order to be satisfying for the average user. Again, respective standards are
country specific and can be set under administrative control. The volume of received call
progress tones can be adjusted by the telephone volume control.

Codecs

Codecs (Coder-Decoders) convert between analog voice signals and digital signals. Avaya
supports several different codecs offering varying bandwidth usage and voice quality, including:
A G.711 codec produces audio uncompressed at 64 kbps
A G.729 codec produces audio compressed at 8 kbps
A G.723.1 codec produces audio compressed at 5.3 kbkps or 6.3 kbps
Table 41: Comparison of speech coding standards (without IP / UDP / RTP overhead)
page 212 provides comparisons of several voice quality considerations associated with some of
the codecs supported by Avaya products.
Note:
Toll-quality voice must achieve a MOS (Mean Opinion Score) of 4 or above. The
Note:
MOS scoring is a long-standing, subjective method of measuring voice quality.
Codecs
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