/mcpand/or gaps of absolute silence between sentences. Refer to Troubleshooting Hissing and Static for more information. If these tuning techniques do not solve the problem, then disable VAD. This results in a loss of bandwidth savings. Resolve Hissing and Clipping Problems in One Direction VAD is the cause of most hissing problems. Therefore, it is important to identify whether it is enabled. One of the first steps to troubleshoot hissing or front-end clipping of sentences is to disable VAD. It is therefore important to be able to identify whether it is disabled. If hissing or clipping only occurs in one direction, the outbound direction, then it can be due to VAD being enabled in this direction even though you have tried to disable it in the VoIP dial peer. In this case, the show call active voice command shows VAD enabled and the PeerID in use being 0. In order to overcome this issue, configure the incoming called-number <number_dialed> (registered customers only) command on the VoIP dial peer to ensure that calls to the PSTN match this peer at the gateway. Otherwise, calls in this direction match with the default dial peer that has VAD enabled by default. Echo These parameters are important to troubleshoot echo: ACOMLevel=20 OutSignalLevel=-64 InSignalLevel=-58 ERLLevel=20 The test tone output is -15 and is looped back with 0 dB loss. Therefore, it comes back at -15 dB. The ERL value here has no significance at this point since the echo canceller does not consider the input signal to be echo. Note: The OutSignalLevel shows the value of the level after the output attenuation is applied to the signal. The InSignalLevel shows the value of the level after the input gain is applied. If the ERL value is too low, the echo signal that returns to the gateway might be too loud (within 6 db of the talker signal). This causes the echo canceller to consider it as voice (double-talk) instead of echo. Therefore, the echo canceller does not cancel the echo. ERL should be between 6 db and 20 db in order for the echo canceller to engage. Refer to Troubleshooting Echo Problems between IP Phones and Cisco IOS Gateways and Troubleshooting Echo in IP Telephony Networks (Audio on Demand) for information on troubleshooting echo problems.