Echo cancellation

What is echo cancellation?

Echo cancellation is used in telecom and telephony applications to improve the quality of voice communication. It prevents echos from being created or captured. It can also remove the echo in post-processing. Echo cancellers operate by first analyzing the incoming voice stream and simultaneously monitoring the return voice stream before it’s being transmitted. If the echo is detected, the echo cancellation engine subtracts it from the transmitted or received audio signal.

Echo is typically created either when a microphone picks up the voice from the speaker and broadcasts it back to them (this is referred to as acoustic echo), or when electrical signals encounter an impedance mismatch in the telephone network (this is known as line echo). Thus, echo cancellers can be classified into two types: acoustic echo cancellers (AEC) and line echo cancellers (LEC).

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An adaptive filter is a vital component of acoustic echo cancellation systems. The basic principle of adaptive echo cancellation algorithm is to simulate the echo path, generate a replica of the echo, and then subtract it from the received voice signal.

When is acoustic echo cancellation required?

Acoustic echo usually occurs when the speaker volume is very high, when the microphone and the speaker are in very close proximity to one another, or when a highly sensitive microphone is used. While an echo with a delay of less than 40ms is not likely to be perceived by a human ear, anything over 40ms starts to become noticeable and it might sound irritating to the listener.

In the call center environment, acoustic echo can stand in the way of efficient customer communication. Not only is it annoying to both sides of the interaction (call center agents and customers), it can result in misunderstandings and important information being missed. That can ultimately decrease the overall customer experience as well as call center performance. This is why acoustic echo cancellation and removing noise from calls are essential to ensuring efficient interactions in call centers.

How IVR works

Echo cancellation is also required in Interactive Voice Response (IVR) systems that employ automatic speech recognition (ASR). It helps prevent an echo from the prompt being played to the caller. It also improves the accuracy of speech analytics.

How can I prevent my video calls and microphone from echoing?

Whether it’s customer support calls or conference calls with co-workers, dealing with acoustic echo and background noise can be a challenge. Here are some of the basic steps you can take to prevent echoing during voice and video calls.

Wear headphones

One of the fastest and easiest ways to eliminate echoing is by simply using headphones. Since there is no sound coming out of the speakers (as the speakers are in your ears), the microphone is not likely to pick it up which avoids echoing. That can be applied to both one-to-one video calls and group conference calls.

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Adjust your volume level

When your speaker volume is too high, your microphone can pick up the voices of other call attendees causing an echo that you might not even be aware of. Turning down the volume and properly adjusting your microphone sensitivity settings ensures your microphone will only pick up your own speech.

Enable half duplex communication

Another quick way to eliminate echoing is by using half duplex communication, where only one speaker’s audio is transmitted at a time. That means having all the participants of a call mute themselves when they are not speaking. The downside of this approach is that the call could not feel like a natural, uninterrupted conversation.

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Frequently asked questions

What is echo cancellation?

Echo cancellation technology is used in telephony to remove echo and other unwanted white noise. It helps with speech enhancement and audio clarity on both ends of the line. It operates by monitoring the incoming and outgoing audio stream and subtracting the echo from the transmitted or received signal once it’s detected. Echo cancellers are commonly classified into acoustic and line echo cancellers.

When is acoustic echo cancellation required?

When an acoustic echo becomes audible to the human ear (typically at a delay of about 40ms), it can significantly impair voice quality and create an unpleasant experience. That can be critical in the call center environment (especially in busy call centers), where an acoustic echo canceller may be required to ensure smooth and uninterrupted call center interactions.

How do I stop my video calls and microphone from echoing?

Using headphones and turning down the volume of your microphone as well as properly adjusting its sensitivity settings are some of the quickest ways to avoid echoing in both one-on-one and group conference calls. You can also enable half duplex communication by having all the call attendees mute their microphones when they are not speaking.

How do I turn off echo cancellation?

While at most times echo cancellation works well in helping you eliminate echoes and surrounding noise, it can cause the audio to sound muffled in the recording when you are having a full duplex conversation (talking simultaneously with another speaker). In cases like that, you may want to disable echo cancellation - it can usually be turned off in the audio settings of the device you are using.

What causes an echo?

An echo happens when a sound wave reflects off a surface (walls and/or objects) and is repeated back to the original speaker. In the context of telephony and telecommunication apps, echo can be caused when a speaker volume is very high, when sensitive microphones are used or when the speaker and the microphone are positioned very close to one another.

Should I enable acoustic echo cancellation?

Acoustic echo cancellation is used to remove acoustic feedback between a speaker and a microphone in telecommunication and teleconference systems. It should be enabled in situations where echos may occur. This is to enhance the audio quality and ensure clear, uninterrupted natural communication.

Are there microphones that cancel background noise?

Noise-canceling microphones are designed to pick up your voice while eliminating the background noise. They are often used in busy call centers where agents are located close to each other. The noise-canceling effect is achieved in different ways. For example, by using two or more built-in microphones that pick up the sound from different directions and subtract the surrounding noise from the input signal.

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