When editing in Pro Tools, you will often come across audio clips that have large portions of silence (or near-silence) that you want to quickly edit and remove. Using Strip Silence you can quickly edit across an entire selection, removing the need for multiple manual edits, and speeding up your workflow.
Whenever you record an instrument for a song, there may be natural pauses in between phrases or sections. Unless the instrument is playing continuously for the entirety of the recording, your resulting audio track will contain moments of silence. However, these moments of "silence" are not entirely silent: the hum of the lights, the sound from an air conditioner, the rustle of the musician adjusting their position, or even mic-bleed from other instruments in the studio are all potential noises that will be recorded into the final take. When you’re editing your audio clips, you will want to remove these unwanted noises, so you’re just left with the instrument you’re recording.
Strip Silence is an editing technique in Pro Tools that analyzes audio selections-”across multiple clips or tracks-”and automatically identifies audio events above a specified threshold level. You can then "strip," or remove, any audio selections that do not exceed the stated threshold, leaving the desired audio in place. In essence, Strip Silence functions as an editorial version of a gate-”it cuts out audio selections that fall below a certain dB threshold.
A very common application of Strip Silence is to clean up the recorded audio from rack/floor toms from the drum kit. When miking a drum kit, it’s common to use a separate microphone for each drum: kick, snare, cymbals, and each tom. Since toms are used relatively sparingly (compared to the kick, hi-hat, and snare), you may be left with many stretches of silence on the tom tracks. You can use Strip Silence to quickly remove these stretches, since they will contain mic bleed from the other parts of the drum kit.
For example, in the figure above, I have the clip on the RACK TOM audio track selected. Just from looking at the audio waveform, we can see big spikes in audio along with longer stretches at a sustained audio level. The audio spikes are the moments when the tom is being hit, and everything in between is bleed-through from the rest of the kit. To tighten up the mix of this drum kit, I want to remove all the sections where the tom is not playing. I will use Strip Silence to achieve this goal.
To access the Strip Silence window, choose Edit > Strip Silence or press Command+U (Mac) or Ctrl+U (Windows).
The Strip Silence window contains four slider controls that allow you to adjust the parameters for the silent areas of a clip. As you adjust these sliders, rectangles will appear on the audio clip, indicating which areas will remain after stripping the silence away. Here are the functions of the four parameters:
Strip Threshold sets the amplitude threshold for the Strip Silence operation. Audio below the threshold is considered silence and will be removed while audio above the set threshold will be retained.
Minimum Strip Duration sets the minimum duration for the material below the threshold that will be removed. Use this parameter to avoid creating numerous small clips within a selection.
Clip Start Pad specifies a time value to be added to the beginning of each new clip created with Strip Silence. This helps preserve the audio that falls below the threshold at the beginning of an audio passage. The breath of a singer before singing the first note, a finger sliding before a guitar chord, etc.
Clip End Pad specifies a time value to be appended to the end of each new clip, preserving nuances in the decay of the material.
To properly set your Strip Silence parameters, raise the Strip Threshold slider until boxes start to appear around all the transients in your selection. Keep raising the Threshold slider until the boxes remain only around the transients you wish to keep-”in my case, only the tom hits remain outlined. I raised the Min Strip Duration slider so that tom hits that occur in rapid succession are not separated from each other. Then, use the Clip Start Pad and Clip End Pad to adjust the beginning and end points of the selection. In my case, I don’t need a long Clip Start Pad as the attack of the toms is very sudden, but I do want to preserve the natural decay of each tom hit, so I increased the Clip End Pad slider a bit.
When you are happy with your selection click "Strip." Strip Silence is non-destructive, so if you’re not happy with your selection after the fact, you can hit "Undo" and readjust your parameters.
As you can see, after using Strip Silence, only the desired tom hits on my track remain on separate clips. Using Strip Silence was a much faster process than manually trimming my clips to remove the unwanted portions. Of course, you still may need to do some fine tuning after using Strip Silene, e.g., trimming remaining clips if they’re too long/short, adding batch fades to your clips, etc.
If you look at the bottom of the Strip Window, you will notice Strip Silence provides two additional functions: Extract and Separate.
Extract is the inverse function of Strip. It will remove all the audio events that exceed the threshold, leaving the "silent" portions of the track. This can be used in post-production projects to generate room tone or ambience.
Separate will separate the clips based on the designated Strip Silence boundaries without removing any audio.
Strip Silence is a very effective method for removing the unwanted silence from your audio clips. It is utilized in both Music Production, and Post Production. This tool can be a huge time-saver when editing dialogue tracks for Television, and Film. Also, the ability to extract the silence can give Sound Designers a quick way to capture room tone for a scene, and layer it quickly with other sound elements. The same techniques can be applied to Podcasts, AudioBooks, or Radio Shows.
As for Music Production, the same methodology with Strip Silence is applied to Vocals, Guitars, Drums, etc...
Try using this in your own session work. Take your time and see how it reacts with different setting options. Very quickly you will discover the settings that work best for you, and will start flying through edits.
Alex Thomen
Author: Alex Thomen
Composer / Arranger / Pro Audio Instructor
ProMedia Training, LLC
www.protoolstraining.com
888-277-0457