1. A method for monitoring voice quality in a communication network, comprising: establishing a first voice communication pathway between a first mobile telephone and a voice server via the communication network; concurrently with said establishing the first voice communication pathway between the first mobile telephone and the voice server, establishing a second communication pathway between a second mobile telephone and the voice server via the communication network; wherein each of the first and second mobile telephones and the voice server operate in a first mode of operation in which either one of the first or second mobile telephones transmits a first voice test message via the communication network and the voice server is configured to receive the first voice test message; wherein each of the first and second mobile telephones and the voice server operate in a second mode of operation in which the voice server transmits a second voice test message via the communication network and either one of the first or second mobile telephones is configured to receive the second voice test message; establishing synchronicity between the first mobile telephone and the voice server to repeatedly alternate between the first mode of operation and the second mode of operation by triggering an initial message in an initial mode of operation, which can be the first or second mode of operation, wherein said establishing synchronicity between the first mobile telephone and the voice server comprising listening to at least part of the initial message, and continuing listening for a period of time after the end of the initial message; concurrently with establishing synchronicity between the first mobile telephone and the voice server, establishing synchronicity between the second mobile telephone and the voice server to repeatedly alternate between the first mode of operation and the second mode of operation; and determining a voice quality for each of a plurality of first voice test messages received by the voice server.