Echo

Echo has long been an issue in telephone networks. You have certainly experienced some echo on a landline or cellular phone. VoIP introduces new variables and still must deal with the old issues. While the user experience is similar, there are different types of "echo" to deal with in a voice call.

The first issue is acoustic coupling, which means feedback from the speaker into the microphone, which requires acoustic echo cancellation. You experience this with speakerphones and room conferencing systems. Early PC voice applications did not have acoustic echo cancellation. It is technically a difficult problem with much variability, since it depends on the room you are in-how big and what kind of surfaces, etc. Modern PC designs are now capable of acoustic echo correction, but it remains the most common problem in PC voice applications. One reason we like Skype is that echo is very well handled and virtually not a problem.

This acoustic coupling issue is especially common in desktop applications where it cannot always be effectively cancelled. Some years ago this was not handled at all by applications. Today that is quite rare and you should not experience significant echo problems with a bit of thought in use. You notice this as the "other person's problem" so someone will usually tell you when they get the feedback. Be sure not to have the speakers too loud, nor facing the microphone. If you shield the microphone location it will be a big help. Of course a headset is a big help-and a well designed adapter to a standard telephone will also help. So if you still find echo, where does it come from?

Real echoes are generated in the network and anywhere there is an interface between the Internet and conventional telephone line, including any phone that you may connect to your PC. Each echo is best handled "locally," wherever it is created. Echo from your microphone and speaker or from an attached telephone can be handled in PC software or in attached hardware which must be functioning to maintain a high quality.

Occasionally you will experience intermittent echo problems that are occurring within the network. Newer equipment in most networks keeps this echo to a minimum. There is a technical detail of "training" echo cancellation equipment that may not work occasionally and you will observe unusually high echo. Typically placing the call again will take care of such matters, or you may need to find another service provider.

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