What is Echo Cancellation?

8 min read
May 18, 2023

In today's hyper-connected world, clear real-time communication is more important than ever. And nothing can disrupt a conversation like an onset of echo during remote team meets and conferences. When a speaker hears their voice reverberating back to them, it can be distracting or even impossible to comprehend the conversation. 

Even a small echo can make a big difference, with an amplitude of just 25 milliseconds being enough to cause audible disruption. This is where echo cancellation technology comes in, contributing to smooth and uninterrupted audio and video communication.

Table of Contents 

  1. Understanding echo and its types
  2. What is echo cancellation and how does it work?
  3. Why is echo cancellation critical?
  4. How to prevent video calls and microphone from echoing?
  5. What is noise reduction?
  6. Noise reduction and echo cancellation
  7. Experience lag-free video communication with Digital Samba

In this blog, we’ll discuss echo cancellation, how it works, and how it makes audio/video communications a seamless and productive experience. 

What is echo and its types

Echos can be quite frustrating, which deteriorates the overall quality of audio call conversations, video conferencing, or live presentations and results in time and productivity loss. 

Here are the two main types of echo: 

Hybrid/ line echo

Hybrid echo usually occurs in remote telephonic connections. It is mainly an electrically generated echo that happens when it encounters an impedance mismatch in a hybrid network by the conversion of 4-wired phone circuits to 2-wire circuits.

In digital transmission lines, hybrid echo is less problematic than analogue or traditional transmission lines. This is because digital systems utilise sophisticated signal processing techniques to efficiently identify and remove echo, improving audio quality and clearer communication.

Acoustic echo

Acoustic echo is common in audio and video conferencing and is always heard on the listener’s end. It is produced when the microphone couples with the speaker and broadcasts the audio back. As a result, participants hear echoes. 

There can be various factors behind acoustic echo production, such as a sensitive microphone, the speaker’s volume being much higher, or sound reflection from the external surface. 

Understanding Echo and Its Types

What is echo cancellation and how does it work?

Echo cancellation is crucial for any service provider providing real-time communication to its users. 

The echo canceller's main objective is to identify unwanted echoes being captured or produced, eliminate them in post-processing, and in turn, enhance the sound quality of a voice/video call for smooth real-time conversations.

Echo cancellation process

Nowadays, in telecommunication networks, echo cancellers are generally placed in their dedicated digital circuits. The echo cancellation process involves two essential steps that ensure clear communication. Let's discuss these in detail:

Step 1: Using adaptive filter

The echo canceller utilises a digital adaptive filter that learns about the unique characteristics of the voice signals and echoes travelling through it. When a voice path reaches the cancellation system, the echo canceller compares the incoming signal with its learned model to dynamically cancel any existing echo. 

This intelligent process effectively removes more than 80% of echo across the network, resulting in clearer communication.

Step 2: Employing a non-linear processor (NLP) 

Despite the initial cancellation efforts, there might still be some faint traces of echo present. To tackle this, a particular non-linear processor (NLP) comes into play, attenuating the remaining residual echo by making it quieter than the surrounding noise. 

This final step ensures that even the slightest echo traces will be mitigated, providing a high-quality communication experience.

Why is echo cancellation critical?

Echo cancellation is critical for experiencing disruption-free real-time conversations. Here we will discuss some key effects of unwanted echoes, which can disrupt productivity. These include:

Additionally, if there is already a lag in the network connection,  echoes will only worsen the situation by preventing participants from active contributions.

An echo-free environment can benefit your business through improved audio quality, enhanced communication, and better user experience. 

With that, it can also prevent excessive bandwidth usage by mitigating unwanted echoes from being transmitted as data. 

How to prevent video calls and microphones from echoing? 

Whether it's a one-on-one voice call or a conference video call with multiple participants, here is a list of a few steps to prevent echoing during important voice/video calls.

  • Use headphones: It is the most convenient and straightforward method to get an echo-free call right on the spot. Since no sound is coming from speakers, no signals are picked up by the microphones. 
  • Adjust speaker’s volume level: If the speaker’s volume is high, your microphone can easily couple with speakers causing echoes. Adjusting the microphone sensitivity and maintaining a moderate volume level can help alleviate the problem, so you won’t need to sigh in frustration. 
  • Use a high-quality microphone: Investing in a premium microphone isn’t a bad idea that comes with echo and active noise cancellation features resulting in clearer audio.

How to Prevent Video Calls and Microphone From Echoing

  • Sit away from surfaces that reflect sound: Improving room acoustics is another way to avoid echoes. The simple method is to reduce reflective surfaces, such as bare walls and glass surfaces, and increase absorbent surfaces, such as carpets, curtains, acoustic panels, etc. 
  • Enable half-duplex communication: To prevent echoing, one alternative is to adopt half-duplex communication, which permits transmitting audio from only one speaker at a time. This mode allows only one speaker to use a microphone while others mute their mics when not speaking. 

However, one clear disadvantage of this mode is that it won't feel like a natural conversation, as each participant will have to wait for their turn to speak. 

What is noise reduction?

Noise reduction, often termed noise elimination or noise suppression, refers to the process of removing unwanted ambient sounds from an audio signal. In the realm of digital communication and audio processing, this technique is crucial for enhancing the clarity and quality of the transmitted sound.

Noise reduction, noise elimination, and noise suppression are terms often used interchangeably in the context of audio processing, but they can have subtly different meanings depending on the specific application and the extent to which the unwanted noise is managed:

  1. Noise reduction: This is a general term that encompasses various techniques used to reduce the level of background noise in an audio signal. The goal of noise reduction is not necessarily to obliterate all unwanted noise but to decrease it to a level where it’s less intrusive or distracting. It’s about improving the quality of the sound by diminishing the presence of noise.

  2. Noise suppression: Similar to noise reduction, noise suppression refers to the process of minimising background noise. However, suppression often implies a more active process of identifying and attenuating specific types of noise, such as wind noise in microphones or electrical noise in communication systems. The term suggests a targeted approach to reducing specific kinds of noise without eliminating them.

  3. Noise elimination: This term suggests a more absolute removal of noise. In practice, eliminating all noise from an audio signal is very challenging and often not feasible. However, the term might be used to describe processes that aim to remove as much noise as possible, often in specific settings like noise elimination in audio recordings or certain professional audio engineering contexts.

When we discuss what is denoise, we're delving into the methods and technologies used to reduce noise in audio streams. This can include anything from the hum of an air conditioner to the buzz of traffic in the background. Noise reduction technology works by identifying the consistent sound patterns of this background noise and then filtering it out or suppressing it, allowing the primary audio, like a person's voice, to be heard more clearly.

This process is particularly important in environments where the background noise can be distracting or when speech clarity is paramount, such as in video conferencing, call centres, and voice recording studios. Effective noise reduction enhances the listener's experience by providing a cleaner, clearer audio signal, free from disturbances that can obscure the main audio content.

In practice, noise reduction algorithms are complex and operate in real-time, analysing the audio signal for characteristics of noise and then applying various digital filters to mitigate or eliminate these unwanted sounds. The result is a more intelligible and pleasant listening experience, crucial for effective communication in today’s digitally connected world.

Noise reduction and echo cancellation

Noise reduction and echo cancellation are related but distinct features in audio processing, especially in the context of telecommunication and video conferencing systems.

  1. Noise reduction: This refers to the process of removing unwanted background sounds from an audio signal. Noise can come from various sources like traffic, fans, or even keyboard typing. Noise reduction algorithms work to identify and filter out these extraneous sounds, enhancing the clarity of the primary audio signal (e.g., a person's voice). The goal is to make the conversation more intelligible by reducing background noise.

  2. Echo cancellation: Echo occurs in audio systems when the sound output from a speaker is picked up by a microphone and then retransmitted back through the system. This creates a delayed repetition of the sound, which can be distracting or disorienting. Echo cancellation involves detecting these echo signals and removing or reducing them before they become audible to the listener. This is particularly important in scenarios where speakers and microphones are nearby, such as in speakerphones or video conferencing setups.

In summary, while both features aim to improve audio quality, noise reduction focuses on eliminating background noise, whereas echo cancellation specifically targets and mitigates the issue of echo in audio communications.

Experience lag-free video communication with Digital Samba

Digital Samba is a video conferencing API & SDK that ensures lag-free audio/video conversations with people across different time zones. It allows you to incorporate real-time video streaming via WebRTC into your product, creating a seamless user experience. With our video conferencing API, you can effortlessly manage all aspects of your conferences while customising user experience with our client SDK. 

Furthermore, our products are GDPR compliant and end-to-end encrypted (E2EE). With features like user management, speaking permissions, shared notes, file sharing, email automation, and more, we ensure uninterrupted real-time video/audio communication. 


What is the difference between noise suppression and echo cancellation?

Noise suppression reduces background noise, while echo cancellation specifically targets and removes echo from audio signals.

What is the principle of echo cancellation?

Echo cancellation works by identifying the echo path and generating an inverse signal to cancel out the echo in real-time communication.

What is the difference between echo cancellation and noise cancellation?

Echo cancellation removes echo from audio, whereas noise cancellation focuses on eliminating ambient sounds for clearer audio.

What causes a microphone to echo?

A microphone may echo due to feedback from speakers, poor room acoustics, or incorrect audio settings causing sound to be picked up and re-amplified.

What is an example of echo cancellation?

An example of echo cancellation is a conference call system automatically eliminating echo caused by speakers and microphones being too close.

How do I stop my mic from echoing?

To stop your mic from echoing, use a headset, adjust the microphone's position, reduce speaker volume, or enable echo cancellation features in your software.


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