Remove AC Background Rumble in Audacity

Continuous air conditioner noise can ruin an otherwise clean audio recording, but it can be easily removed using Audacity’s built-in audio processing tools. This guide covers a fast, two-step method to eliminate low-frequency air conditioning hum and steady ambient hiss using the High-Pass Filter and the Noise Reduction effect without degrading your primary voice track.

Step 1: Apply a High-Pass Filter

Air conditioning units produce heavy sub-bass vibrations and low-end rumble that typically sit below 80 Hz to 100 Hz. A high-pass filter cuts these low frequencies immediately while leaving human speech unaffected.

  1. Open your audio file in Audacity.
  2. Select the entire track by pressing Ctrl + A (Windows) or Cmd + A (Mac).
  3. Go to the top menu and select Effect > EQ and Filters > High-Pass Filter.
  4. Set the Frequency (Hz) to 80 (or 100 for heavy mechanical rumble).
  5. Set the Roll-off (dB per octave) to 12 dB or 24 dB.
  6. Click Apply.

This removes the deepest mechanical hum before you apply more aggressive noise reduction.

Step 2: Capture a Noise Profile

The Noise Reduction tool requires a sample of the isolated air conditioner sound so it knows precisely which frequencies to remove.

  1. Highlight a 2- to 3-second section of your recording that contains only the air conditioner sound (a pause where nobody is speaking).
  2. Go to Effect > Noise Removal and Repair > Noise Reduction.
  3. In Step 1 of the dialog window, click the Get Noise Profile button. The window will close automatically.

Step 3: Apply the Noise Reduction

Once Audacity has analyzed the noise profile, apply the suppression across your entire recording.

  1. Select your entire track again using Ctrl + A or Cmd + A.
  2. Return to Effect > Noise Removal and Repair > Noise Reduction.
  3. In Step 2 of the window, adjust the following parameters to ensure the audio sounds natural:
    • Noise reduction (dB): Set between 6 and 12. Higher settings can make the voice sound metallic or hollow.
    • Sensitivity: Set between 5 and 7.
    • Frequency smoothing (bands): Set between 3 and 6 to keep the transition smooth.
  4. Ensure the Noise radio button is set to Reduce.
  5. Click Preview to check the results. If the voice sounds distorted, lower the Noise Reduction (dB) slider.
  6. Click OK to process the audio.