Using Audacity Spectral Edit Multi Tool for Notch Editing

The Spectral Edit Multi Tool in Audacity provides a visual, surgical approach to audio restoration by combining spectral selection with frequency-specific filtering. By switching an audio track to Spectrogram view, users can visually locate unwanted noises—such as electrical hums, mic whistles, or equipment squeals—and apply a narrow notch filter directly to that precise frequency band without compromising the surrounding audio spectrum.

Understanding the Spectrogram View

Before using the Spectral Edit Multi Tool, the track display must be switched from the traditional Waveform view to Spectrogram view. In this mode, the vertical axis represents frequency (measured in Hertz) and the horizontal axis represents time, while color intensity denotes the amplitude of specific frequencies. Narrow horizontal bands of intense color indicate continuous, resonant noises that are prime candidates for notch editing.

How the Spectral Edit Multi Tool Works

The Spectral Edit Multi Tool automatically adapts its behavior based on the cursor's position within a spectral selection:

  1. Center Frequency Identification: When hovering near the center of a frequency selection, the cursor turns into a horizontal line with up and down arrows. Clicking and dragging aligns the center frequency directly over the offending sound.
  2. Bandwidth Adjustment: Hovering over the upper or lower frequency boundaries reveals a resizing cursor. Dragging these boundaries defines the bandwidth (Q-factor), allowing you to make the notch as narrow or as broad as necessary. A narrower selection isolates the target noise while preserving neighboring harmonics.
  3. Contextual Action: The Multi Tool acts as a consolidated interface for Audacity’s individual spectral editing effects (Spectral Edit Parametric EQ, Spectral Edit Shelves, and Spectral Edit Multi Tool). Depending on where the selection boundaries lie relative to the track's frequency range, the tool determines whether to apply a low-shelf, high-shelf, or notch filter. When both an upper and lower frequency boundary are defined, it defaults to notch or parametric filtering.

Executing the Notch Edit

To perform a frequency-specific notch edit:

  1. Use the Selection Tool (F1) to highlight the time region containing the unwanted noise.
  2. Define the frequency range by dragging vertically across the target frequency on the Spectrogram.
  3. Adjust the center line directly over the fundamental frequency of the noise and tighten the top and bottom boundary lines around it to minimize collateral audio loss.
  4. Navigate to Effect > Spectral Edit Multi Tool (or apply it via a configured shortcut). Audacity calculates the notch filter based on your defined center frequency and bandwidth, drastically cutting the amplitude at that exact band while leaving frequencies above and below completely intact.