Understanding Clicks and Pops in Audio

Unwanted clicks and pops are short-duration, high-amplitude transients that can arise from various sources during recording and editing. These artifacts often result from digital glitches, such as buffer underruns or clock errors, as well as editing artifacts like abrupt cuts or crossfades that don't align at zero-crossing points. Recording issues, including plosives, mouth noises, or electrical interference, can also introduce these noises. In Reaper, you can use spectral analysis tools like the built-in spectrum analyzer or third-party plugins to identify the frequency range and precise location of these clicks. Zooming in closely on the waveform and listening to isolated sections helps pinpoint the exact problem area before applying any corrective techniques.

Essential Reaper Settings for Click Reduction

Configuring Reaper's preferences correctly can prevent many clicks from occurring in the first place. Navigate to Options > Preferences > Audio and adjust the Buffer size to a lower setting (e.g., 64-128 samples) for recording and a higher setting (e.g., 512-1024 samples) for mixing. This reduces the risk of underruns that cause clicks. In Editing Behavior, enable "Snap media items to grid" and set the snap offset to align with zero-crossings when splitting or moving items. Also, check "Automatically apply fades to new media items" under Media Item Defaults to ensure every new clip has a slight fade-in and fade-out. These simple tweaks minimize the occurrence of clicks at the source, making later cleanup easier.

Using Reaper's Built-in Tools for Click Reduction

1. The Item Properties Fade Tool

The Item Properties dialog offers precise control over fade shapes and durations. Select an audio item and press F2 or right-click and choose Item Properties. In the Properties window, you can set custom fade-in and fade-out lengths in milliseconds, which is particularly useful for smoothing out clicks that occur at the start or end of a clip. For clicks that are not at item boundaries, you can first trim the item to isolate the click, then apply a very short fade (e.g., 1-3 ms) to the affected area. Experiment with different fade shapes—Equal Power for a more natural curve or Equal Gain for a linear taper—depending on the material. A quick fade of just 0.5 to 2 ms can eliminate many clicks without altering the perceived attack of the sound.

2. The Dynamic Split Tool

The Dynamic Split tool is designed to automatically detect and split audio at transient points, including clicks. Select the region containing the click, then press Ctrl+Shift+L (or go to Item > Dynamic Split). In the Dynamic Split window, adjust the Threshold slider so that only the unwanted clicks trigger splits, while ignoring desired transients. Once split, you can select the small segment containing the click and either delete it (creating a gap that you can crossfade) or apply a volume envelope to reduce its gain. The Split at zero-crossing option ensures clean splits that minimize new clicks. For complex passages, use the Preview button to check the results before committing. This tool is especially effective for removing clicks from vocal takes or acoustic instruments where the click is louder than the surrounding signal.

3. The Item Fade In/Out

Beyond the basic fade handles, Reaper allows you to set fades with extreme precision. Click and drag the fade handle at the top-left or top-right corner of the item. For more control, hold Shift while dragging to make fine adjustments. The fade shape can be changed by right-clicking the fade area and selecting from options like Linear, Equal Power, or Smooth Sine. A short fade of 1-3 ms is often enough to remove a click without being audible. You can also combine fades with time selection automation: create a time selection around the click, then apply a quick fade via Item > Fades > Fade In/Fade Out to the selected area. This technique is ideal for clicks that occur in the middle of a sustained note or vocal phrase.

4. The Glue Tool and Crossfades

When you have split an item to isolate a click, the next step is to merge adjacent items smoothly. Select the two items on either side of the removed click, then press Ctrl+Shift+G or right-click and choose Glue items. This creates a new consolidated item that can have a default crossfade applied automatically. Alternatively, use the Crossfade tool by selecting the overlapping area of two items and adjusting the crossfade length. For clicks that are not fully removed by a simple fade, a crossfade of 5-10 ms that splits the difference between the two sides often yields the cleanest result. Enable Snap to zero-crossing in the snapping options to ensure that the crossfade points align with waveform zero-crossings, further reducing the chance of introducing new clicks.

5. Volume Automation with Envelopes

For clicks that are too close to important audio to split or fade, volume automation offers a surgical approach. Add a volume envelope to the item (Item > Take > Volume Envelope) or to the track itself. Create an envelope point just before the click and another just after it, then lower the envelope at the point of the click to reduce its gain. Use a very short automation curve (1-3 ms) to avoid an audible dip. To do this, right-click the envelope segment between the two points and choose Curve shape > Linear or Slow start/end. This method works well for clicks that happen on a strong attack, like a snare hit or a plucked string, where splitting would affect the transient nature of the sound. The automation curve can be adjusted by dragging the curve itself or by adding intermediary points for a more precise shape.

Advanced Click Reduction Techniques

Working with Spectral Peaks

Reaper's spectral editing capabilities, found in the Spectral Peaks mode, allow you to visualize clicks as bright vertical streaks in the spectrogram. Select the Spectral Peaks view from the item's right-click menu or press Ctrl+Shift+E. In this mode, you can lasso the click artifact directly on the spectrogram and press Delete to remove it. This technique is particularly powerful for clicks that are isolated in frequency, such as electrical buzzes or high-frequency digital noise. The Spectral Edit tool also includes options like Attenuate and Mute for more subtle removal. For best results, zoom in to the time scale where the click is visible and use a tight selection around the artifact. After deletion, Reaper automatically fills the gap with surrounding spectral content, often producing a seamless repair.

Using ReaFIR for De-Clicking

ReaFIR, Reaper's native FFT-based dynamics processor, can be configured for noise reduction and click removal. Insert ReaFIR on the track (FX > ReaFIR) and select the Subtract mode. In this mode, you can use the Auto-build noise profile feature. First, select a short region of the audio that contains only the click (no desired signal). Click Add profile from selection, then move the selection to a region with only the desired signal. Ensure the FFT size is set to a value that captures the click's transient nature—typically 256 or 512 samples for moderate latency. Enable Reduce noise and adjust the Noise reduction amount slider carefully. Too much reduction can create water-like artifacts. For clicks in the midrange, try a Bottom line setting of around 10-20 to preserve the harmonic content below the click. ReaFIR works best on sustained sounds like ambient recordings or pad sounds where clicks stand out clearly from the background.

Manual Editing with Zero-Crossing Snapping

For environments where automated tools may be too aggressive, manual editing at zero-crossing points provides total control. Enable Options > Snap media items to grid > Snap to zero-crossing. Then, zoom in to the click and split the item (S) just before the click. Move the edit cursor to a zero-crossing point by holding Shift while clicking on the waveform. Split again after the click, making sure both splits occur at zero-crossings. You can then remove the click segment and crossfade the remaining sections. This technique is time-consuming but offers the highest quality for critical audio, such as dialogue or vocal recordings where artifacts are easily noticed. The key is to ensure that every split and every crossfade starts and ends at a zero-crossing to prevent new clicks from being introduced.

A Practical Step-by-Step Workflow for Click Removal

To apply these techniques efficiently, follow this workflow. First, listen through the entire audio file at a moderate volume and mark any clicks with the M key to create markers. Then, zoom in to each marker and decide the best approach. For clicks at item boundaries, use the Item Properties Fade Tool with a 1-2 ms fade. For clicks in the middle of audio, use Dynamic Split to isolate the segment, then remove or fade it. For clicks that are visible in the spectrogram, use Spectral Peaks for precise removal. For very stubborn clicks, use a combination of volume automation and ReaFIR. After removing each click, listen back at the same volume to ensure no artifacts remain. Finally, render the project and check the result in a different listening environment (e.g., headphones vs. speakers) to catch any remaining issues. This systematic approach reduces the chance of missing a click and ensures consistent quality.

Preventing Clicks During Recording and Editing

Prevention is always better than repair. During recording, use a pop filter to reduce plosives, maintain a consistent distance from the microphone, and ensure that the gain staging is proper to avoid digital clipping. In Reaper, enable Options > Preferences > Audio > Buffering > "Use anticipative FX processing" to reduce the risk of buffer underruns. During editing, always use crossfades when splicing items, avoid cutting on high-amplitude sections, and use the Snap to zero-crossing feature. Regularly clean up your project by removing unused takes and trimming items to their useful sections. These habits will minimize the appearance of clicks and make the removal process when needed much simpler. For more on best practices, check the Reaper official website for community tutorials and Reaper's user forum for specific workflows shared by advanced users.

Conclusion

Reaper provides a comprehensive set of built-in tools for tackling clicks and pops, from simple fades to advanced spectral editing. By understanding the causes of these artifacts and practising a methodical workflow, you can clean up your audio effectively without relying on third-party plugins. Whether you use the Item Properties Fade Tool for quick fixes, Dynamic Split for automatic detection, or Spectral Peaks for surgical precision, each method has its strengths. Combine these techniques with proper recording and editing habits, and you'll achieve cleaner, more professional-sounding projects. For further reading, the Reaper User Guide provides in-depth documentation on all these features, and the Cockos website offers additional resources for audio production.