How can I avoid click artifacts when playing audio in MATLAB App Designer?

I've created a GUI where I'm playing audio files at the click of a button. I've added fades at the front and tail end of the audio file. Still for some reason, I'm hearing slight clicking artifacts at the beginning and end of the audio files. What could be causing this?

I'm using the standard sound() function for playback.

Below is the playback part of the code:

fade_duration = 0.1;
fadeSamples = round(Fs * fade_duration); 
window = hann(2 * fadeSamples); 

fadeIn = window(1:fadeSamples);  
fadeOut = window(end-fadeSamples+1:end); 

new_audio(1:fadeSamples, :) = new_audio(1:fadeSamples, :) .* fadeIn;
new_audio(end - fadeSamples + 1:end, :) = new_audio(end - fadeSamples + 1:end, :) .* fadeOut;

sound(new_audio, Fs);

Answer 1

[Epsilon]

Hi Shaunak,

The playback part of the code provided by you seems to work fine in a MATLAB App. The Hann window being used provides a smooth transition, reducing the chances of click artifacts.

However, if you are experiencing click artifacts, they might be due to the original audio file being clipped or distorted. It's also possible that your playback hardware (such as speakers or headphones) could be introducing these artifacts.

Here are a few suggestions to help eliminate these artifacts:

1. Ensure that the fade window size (‘fadeSamples’) is appropriate for your audio file. If the window is too short, it might not be effective in smoothing transitions.
2. Make sure that the fade-in and fade-out do not overlap or extend beyond the audio data length. This can cause unexpected behavior.
3. Consider adding a short period of silence (zero padding) at the start and end of the audio file, which can help transition smoothly to and from silence.

I've attached the app1.mlapp and audio.wav files used to test the playback part of the code in app1.zip file. I've also added zero padding at the start and end of the audio to ensure smooth transitions.

fade_duration = 1; 
            fadeSamples = round(app.Fs * fade_duration);
            window = hann(2 * fadeSamples);

            fadeIn = window(1:fadeSamples);
            fadeOut = window(end-fadeSamples+1:end);
            
        
            % Add zero padding at the start and end
            zeroPadding = zeros(fadeSamples, size(app.AudioData, 2));
            padded_audio = [zeroPadding; app.AudioData; zeroPadding];

            
            padded_audio(1:fadeSamples, :) = padded_audio(1:fadeSamples, :) .* fadeIn;
            padded_audio(end-fadeSamples+1:end, :) = padded_audio(end-fadeSamples+1:end, :) .* fadeOut;
                   
            sound(padded_audio, app.Fs);

If the problem persists, consider experimenting with different windows as well.

Answer 2

[Rahul]

Hi Shaunak,

I believe that you are hearing clicking sounds, while playing audio files inside a MATLAB App Designer GUI. The clicking artifacts you're hearing are likely caused by abrupt transitions in your audio signal at the beginning and end of the fade-in and fade-out. To address this, you can try applying a linear fade instead of the Hann window. A linear fade ensures a smooth transition from silence to sound and vice versa, eliminating any sudden jumps that could cause clicking noises. To implement this, you can change the fade creation lines to:

fadeIn = linspace(0, 1, fadeSamples)';  % Linear fade-in
fadeOut = linspace(1, 0, fadeSamples)'; % Linear fade-out

This ensures that the audio gradually increases in volume at the start and decreases at the end, removing sharp transitions that cause clicks.

Also, to ensure that the fade-in and fade-out apply smoothly at the boundaries of your audio. If the fade starts or ends too abruptly, it can lead to clicking artifacts. To prevent this, you can ensure that the fade-in starts from 0 and the fade-out ends at 0 by adding the following lines:

new_audio(1, :) = 0; % First sample should be 0 after fade-in
new_audio(end, :) = 0; % Last sample should be 0 after fade-out

Additionally, if you prefer to stick with the Hann window, you could consider using an alternative window like a cosine window, which can provide an even smoother fade and help further reduce any clicking artifacts. To implement this, you can change the fade creation lines to:

fadeIn = cos(pi * (0:fadeSamples-1) / (2 * fadeSamples)); % Cosine fade-in
fadeOut = flip(fadeIn); % Cosine fade-out

Lastly, to ensure the audio signal stays within the valid amplitude range and avoid clipping, you can clamp the values of the audio signal with:

new_audio = max(min(new_audio, 1), -1);  % Clamp values between -1 and 

If the fade duration is too short, it may not allow enough time for the transition to be clearly heard, which could cause abrupt changes and clicking artifacts. You could try increasing the fade duration to see if this helps reduce the clicking sounds

By making these changes, you could achieve smoother fade-ins and fade-outs, preventing sharp transitions and reducing clicking artifacts. Moreover, using the linear or cosine fade windows, along with ensuring the signal stays within the proper amplitude range, could help you achieve a cleaner playback experience.

For more information regarding the usage of 'linspace' function in MATLAB, refer to the documentation mentioned below:

https://www.mathworks.com/help/matlab/ref/double.linspace.html

Hope this helped!