Echo in VoIP

VoIP Echo
VoIP Echo

Echo in Communication Systems

Many of us never even give a thought to echo which is a feature of almost every voice based communication system. But this is only because over the years be have gotten so good at optimizing the traditional PSTN system that even if there is some, we don't notice it. Echo is when speakers themselves hear what they said a short while after they say it. For this to be noticeable, the delay has to be significant – something over 30 to 50 ms. Normally this delay is much lower and is therefore not a problem to us.

VoIP however seems to be more susceptible due to the large number of interfaces that voice traffic needs to pass through before it reaches its destination. At every junction, a small portion of the signal is reflected back – this is a basic property of many electronic systems. When light hits glass for example, most of it passes through but there is always a tiny portion that is reflected no matter how clear the glass happens to be. The challenge is to minimize the impacts of echo so that people can speak without hindrance.

There are many solutions for reducing the impact it has on a call. Some solutions for example implement one-way traffic when the other person is talking. Though this works in some cases, it fails when both individuals are speaking. It can also lead to queer "breaks" in the telephone call that can be worse than the echo itself.

Echo cancellation however is one of the most promising techniques by which we can minimize the problems. Simply put, the algorithms themselves filter out repetitive signals that they identify as echo. This filtering can happen at any point along the process. Preferably, the VoIP enabled routers would be able to implement these algorithms early on and so prevent the transmission of the echo from reaching the user in the first place.

Other solutions to echo involve reducing the amount of VoIP latency which is a significant problem because the signal has to jump through many entities before it reaches its destination. First to the ISP, then to the VoIP provider, then to the telephone junction and finally the user. Most VoIP clients automatically implement echo cancellation to improve the VoIP sound quality. To reduce latency, contact a local New York IP PBX provider so as to minimize the distance traveled by the signal.

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