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What is Echo Cancellation?

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  • Written By: Malcolm Tatum
  • Edited By: Bronwyn Harris
  • Last Modified Date: 28 November 2016
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    Conjecture Corporation
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Echo cancellation is a process that is employed in the telecommunications industry, and refers to strategies that are used to reduce the amount of echoing that can occur during different types of audio communications. The use of this form of acoustic echo reduction can make it much easier for all parties involved in the communication to hear and be heard clearly. Today, the actual process of echo cancellation can be achieved using software as well as equipment designed to isolate the origin of the echoing and suppress that portion of the network signal.

As the name implies, an echo on a telephone communication is a reverberation of words as they are spoken. Some have described the effect as being that of someone attempting to talk from the bottom of an empty barrel. The reverberation obscures the words that are being spoken, making it very difficult for the other party to understand what is being said. When some sort of echo cancellation is used, it is possible to prevent this effect from occurring, or identify and eliminate the echo should one appear at some point in the conversation.

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Echo cancellation is an ongoing process that takes place in any type of audio conference call. Not everyone is aware that terminating several different connections into a common conference line can actually magnify any tiny sound issues that would not be noticeable on a single point to point telephone call. As a result, the potential for issues such as echoing is greatly enhanced. This has led to many manufacturers of audio conference bridging equipment to include some type of digital signal processor in the basic bridge design. For the most part, the bridge can read the inbound signals received from phone networks and filter them so that the chances of echoing are minimized.

There are situations when the underlying cause of the echoing is so pronounced that communication equipment cannot completely filter out the sound issue. When this is the case, many people choose to simply end the current connection, then establish a new one. Since it is highly unlikely that the second connection will make use of the same phone circuits and channel banks on the phone switches involved, this often clears up the echoing and allows the participants to continue their discussion.

When echoing occurs on an audio conference, there is no need for everyone to disconnect from the conference and reestablish a new one. Most conference call bureaus employ operators who are available to troubleshoot any type of sound issue that occurs during the conference. Once a conference operator is alerted to the problem, he or she can use bridge software to isolate the origin of the echoing to a particular line in the conference, and take appropriate action. If the origin of the problem is found to be the point of termination itself, the operator can establish a new conference and transfer all parties, without anyone having to disconnect.

In rare cases, echo cancellation may be impossible to manage. This can be true in situations where there is significant damage to telephone switches or other portions of the network that carry phone signals. Even with Voice over Internet Protocol or VoIP echo cancellation, there is the potential for technical issues at each end of the transmission, particularly where the online signal is transferred to a local phone switch. In situations of this nature, it may be necessary to wait until repairs are made to the phone facilities before it is possible to continue the audio discussion.

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