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Live audio delay and tremolo effect modules in the browser
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WebFX is an interactive audio-effect app that functions as a delay & tremolo effect pedal for the guitar, microphone, or any other audio input. Users have the ability to digital alter a live analog signal or some provided samples with user controls. Finally, users have the ability to record and download the audio stream.

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WebFX uses the Web Audio API for handling audio input and manipulation. Web Audio gives WebFX the following functionality:

  • Audio Input
  • ON/OFF & Volume Controls
  • Delay effect (speed, length, level, filter)
  • Tremolo effect (speed, depth)
  • Oscilloscope that visualizes live audio signals.

I also used the Recorderjs library to add bonus functionality allowing users to record their audio streams. Since this library isn't currently being maintained, I had to make some edits to methods that have been deprecated.

How It Works

Setting Up Audio

  • audioContext is the interface representing the audio processing graph built from the linked audio nodes described below. Created using Web Audio's new AudioContext()

  • streamSource is an Media Stream Audio Source node containing the live streamed audio signal. Created using Web Audio's audioContext(createMediaStreamSource)

  • sample represents a AudioBufferSourceNode. There are three of these representing the pre-loaded audio samples users can trigger

  • sampleNode is a GainNode attached to the previous sample buffer source nodes

Effect Processing


For Delay to work, both the streamSource and sampleNode are connected to mixNode which is a Web Audio GainNode representing the mix of the delay-effect and original audio source

  • delayEffect is a Web Audio DelayNode, which will repeat the audio signal at a set time, DelayNode.delayTime.value. This value is controlled by the user using the delay 'Speed' slider

  • feedback is a Web Audio GainNode. delayEffect and feedback are connected to each other both ways. The value of feedback.gain.value sets the decay level of the delay feedback loop and is controlled by the user using the delay 'Length' slider

  • filterNode is a Web Audio BiquadFilterNode. filterNode.frequency.value represents the cutoff frequency for the delay effect and is set by the user using the delay 'filter' slider

  • bypassNode is a Web Audio GainNode that sets the output level of the delay effect. It is set by the user using the delay level slider

  • bypassNode is then connected to the mixNode. Now mixNode receives the original audio signal and sample audio (streamSource, sampleNode), and the audio affected by delay


  • To achieve a tremolo effect, a Low Frequency Oscillator (LFO) is connected to the gain of the volume node. The LFOs frequency and gain value determine the speed and depth of the tremolo effect

  • The tremolo effect is achieved by connecting a web audio Oscillator to a GainNode. These are called lfo and lfoAmp

  • The speed of the tremolo effect is controlled by setting the frequency of the LFO oscillator and depth is controlled by setting the LFO amp's gain value.

  • The user controls the frequency and amplitude of the effect using the tremolo 'Speed' and 'Depth' sliders


  • volumeNode (setting the output level of the audio) is connected to volumeAnalyser, a Web Audio AnalyserNode

  • VolumeNode.frequencyBinCount method returns half the value of the Fast Fourier Transform size, representing the number of data values needed for visualization. This is saved to the variable bufferLength

  • dataArray is set to a new unsigned byte array Uint8Array with the bufferLength passed in as an argument. The array's length is equal to the number of data values returned by frequencyBinCount

  • volumeAnalyser.getByteTimeDomainData() takes in the dataArray, copying the current waveform or time-domain data into the unsigned byte array Uint8Array

  • Using canvas, bufferLength, and the time-domain data, we can draw segments of the wave for each point in the buffer at a specific height based on the data point value from the array. The a draw method is called recursively allowing us to see a visual representation of the audio signal in the form of an oscilloscope

WebFX Node Flowchart

This flowchart outlines the relationships between the nodes described above. Next to each node is a comment stating the Web Audio Node object type for each node and how the user can control it.


Implementation Timeline

Phase 1: Figure out audio

  • Get a live audio stream working in the browser
  • Set up control for turning sound and off
  • Set up control for volume
  • Decide on specific parameters and ranges that users can control
  • Start to work on delay effect

Phase 2: Interface

  • Create user controls for delay effects
  • Use interactive knobs or sliders for users to control
  • Have controls for delay speed, intensity, and echo.
  • Explore other ways to modulate tone and frequency spectrum.

Phase 3: Make it pretty

  • Make the project actually look like an effect pedal
  • Test app out with some users, see if the UI is intuitive and easy
  • Add waveform or Fourier spectrum so users can see the audio change as they manipulate it.
  • Add download functionality


Objective: If time permits, I would like to add more effects and possibly turn WebFX into a full effect rack. I am interested in exploring flanger, reverb, and distortion.

Original Concept


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