Beamforming, acoustic echo cancellation (AEC), and noise suppression are the concepts designed to deliver high-quality audio and comfort to the listeners. In any sort of communication or audio recording, the microphone not only captures the sound of the interest but also the unwanted sources of noise like background noise, acoustic echo from speaker to microphone which lowers the sound quality for the far-end user. It becomes imperative to remove these annoying or sometimes unbearable echoes coming from various sources. To provide solutions that can reduce these unwanted noises, technologies like acoustic echo cancellation and noise suppression come into play. Similarly, Beamforming is a concept used in audio signal processing to get the desired signal. Beamforming provides high-quality and intelligible signals from desired source location while attenuates the signal coming from other directions.
Beamforming, Echo Cancellation & Noise Reduction to Deliver High-quality Audio
If we ever speak into any communication device be it mobile phone, speaker, microphone, desktop, we can hear different types of echo/ reverberation coming from different sources. From hearing our voice to loud background noise to some significant delay in audio signals are some of the common problems we face during our daily conversations. These problems require some serious solutions and technologies like Beamforming, Echo cancellation and Suppression play a vital role in controlling it and providing high-quality audio and comfort to the human ears.
For instance, during the video conferencing call, having an echo canceller is needed on both sides of the call to avoid echo. When a person speaks into the microphone, the speech is transmitted through some channel which causes some delay to the signal. The transmitted signal is then delivered to the listener’s loudspeaker and picked up by their microphone. The delayed signal is then transferred back to the original speaker’s room and in that case, the person hears his/her voice as echo which is extremely disruptive. This is where echo cancellation plays an important role to prevent this problem from happening, providing a better quality of sound. When the echo canceller examines the sound going into the microphone and compares it with the sound coming from the far end and then it decides to electronically cancel that signal from transmitted back to the original speaker’s room and thus prevents the echo. That’s why it’s important to have an echo canceller on both sides to avoid either side from experiencing echo.
Figure 1: Application of Beamforming along with AEC in Conference Speakers
Many times, when we talk over the phone or any communication device, we can hear some unwanted background noise that disrupts our conversation. Here comes the main challenge when the microphone has to pick up the audio signal and leave out the background noise. Similarly, in smart speakers where the speech recognition process is performed, the speech signals can be severely distorted by unknown acoustical conditions in users’ homes, which include varying levels of acoustic echo, noise, and reverberation. In such cases, microphone array beamforming is used to improve the quality of recorded audio signals because it enables us to locate and track signal sources. Beamforming with microphone arrays allows the signals to direct sound to a specific location in a room to enhance the speech while suppressing noise arriving from other directions.
Figure 2: Typical Conference Scenario using Microphone Array Beamformer
Noise reduction is the process to eliminate the noise from signal. The noise and echo components significantly restrict the intelligibility of the desired signal and degrade the performance of subsequent audio systems. Therefore, efficient methods for noise reduction are generally desirable which tend to alter signals to a greater or lesser degree. These noises can be crowd noise, machinery, aircraft, background speech, etc.
The noise reduction process is carried out in the areas where noises are generated through machinery, crowd, aircraft, construction sites, transportation, etc. The algorithms always aim to enhance the signal to give a higher signal-to-noise ratio (SNR). It has become a common practice to reduce the noise by employing digital processing methods such as filtering. Various filters like low-pass, high-pass, band-pass are used to alter the frequency ranges based on the incoming noise frequency. They remove the unwanted noise, echo, distortion, and allows the filtered data to pass through the system.
In many communication systems, e.g., telephone, conference device, speakers, the received signals from far-end are always disrupted by background noise as well as by echo signals. In these cases, some noises need to be reduced whereas some need to be cancelled to provide clear and smooth audio to the listeners. AEC and Beamforming process needs to be performed first as a part of audio signal processing then noise reduction process is performed to clean up any extra noise which is left behind in the first process.
Latest audio devices have the potential to transform user’s listening experiences through implementing these technologies. In noise cancelling headphones, where any unwanted ambient noise gets cancelled by going into your ears whereas in the case of smart speakers, the microphone only picks the signal of interest by applying the microphone array beamforming technique.
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