Create an Infinite Delay Feedback Loop in Audacity

This guide explains how to generate a long, naturally decaying feedback loop using the built-in Delay effect in Audacity. By extending the track's timeline with silence, lowering input gain to prevent digital clipping, and configuring decay parameters for a high number of repetitions, you can transform any audio sample into an expansive, self-sustaining delay tail that fades out smoothly over time.

Step 1: Add Trailing Silence to the Track

Audacity terminates applied effects at the end of the current audio selection. Because an infinite or ultra-long decaying delay requires extended time to fade naturally, you must add blank audio space after your original sound.

  1. Click on the track timeline immediately after your audio clip.
  2. Go to the top menu and select Generate > Silence.
  3. Set the duration based on how long you want the decay to last (for example, 30 to 60 seconds) and click Apply.
  4. Press Ctrl + A (or Cmd + A on macOS) to select both the original audio and the newly added silence.

Step 2: Reduce Track Headroom

Each repeated echo in a feedback loop stacks onto the existing audio signal. To prevent the combined repeats from exceeding 0 dB and causing harsh digital distortion:

  1. Select the original audio segment.
  2. Go to Effect > Volume and Compression > Amplify.
  3. Set the Amplification (dB) to a negative value, such as -6.0 dB or -10.0 dB, and click Apply.

Step 3: Configure the Delay Effect

Audacity features a dedicated Delay plugin that allows precise control over decay rate and the total number of iterations.

  1. With the audio and silence selected, open Effect > Delay and Reverb > Delay.
  2. Set the parameters as follows:
    • Delay type: Select Regular.
    • Delay level per echo (dB): Set this between -0.5 dB and -2.0 dB. A value close to 0 dB ensures a very slow, prolonged decay. Setting it strictly to 0 dB produces an infinite repeat without decay, while negative values ensure each iteration becomes progressively quieter.
    • Delay time (seconds): Set the interval between echoes (for example, 0.50 seconds for a standard rhythm or 1.50 seconds for an ambient wash).
    • Pitch change effect: Set to None.
    • Number of echoes: Set this to a maximum or near-maximum value (such as 50 to 100). This allows the feedback to loop continuously across the entire duration of your generated silence until it drops below the threshold of human hearing.

Step 4: Preview and Apply

  1. Click Preview to listen to the first few seconds of the loop.
  2. If the repeats are fading out too quickly, increase the Delay level per echo closer to zero (e.g., change -2.0 dB to -0.8 dB).
  3. If the repeats become louder over time or distort, lower the value (e.g., -3.0 dB).
  4. Click Apply to render the feedback loop across your selection.