To provide better sound quality in telephone conversations, voice communication systems add an acoustic loss of 10 dB between the listener and the speaker. This 10 dB acoustic loss provides the level of sound quality that emulates a scenario where the speaker and listener are only one meter apart and having a face-to-face conversation. Any significant difference from this loss level is audible as too soft or too loud and can result in some degree of listener discomfort.

In IP Telephony networks, the voice communication system implements the 10 dB acoustic loss as follows:

• 8 dB in the telephone of the speaker
• 0 dB in the IP network
• 2 dB in the telephone of the receiver

To account for personal preferences or the presence of background noise, listeners can adjust the volume control of the telephone relative to the 10 dB loss value. The IP Telephony loss values are globally identical and specified in ITU-T Recommendations.

In traditional circuit-switched networks, the telephone that send, receive, and interport line or interport trunk losses are country-dependent. The end-to-end country-specified losses often differ somewhat from the 10 dB loss value. The country-dependency of loss values makes it more challenging to guarantee a proper listener signal level when the PSTN is involved or when signals traverse country borders.

IP Telephony gateways must provide proper signal level adjustments from the IP network to the circuit-switched network and in the reverse direction, and also between circuit-switched ports.

To configure Avaya endpoints across the globe, the devices must be programmed for loss values. To ensure that the signal levels are controlled properly within the scope of a voice network consisting of Avaya systems, customers must administer the appropriate country-dependent loss plan.

In addition to administering loss for two-party calls, Communication Manager provides country-dependent conference call loss administration. Loss is applied depending on the number of parties involved in the conference.