How to Edit Gun Sounds

May 3, 2023
Posted in Tutorial
May 3, 2023 Paul Virostek

How to Edit Gun Sounds

How Pole Prepared our Latest Gun Sound Library

We have over 70 gun sound effects libraries here at Pole Position Production. This week, we introduced one more: our latest firearms collection, The Indoor Gun Acoustics 2 Library. Building upon the popularity of the original Indoor Gun Acoustics library, the new collection features gunfire and performed effects from 6 weapons in 5 new interior spaces.

Gun sound effects are some of the trickiest to capture: they’re loud, dangerous, often hard to record. The work doesn’t end after the recorders are shut off and the microphones are packed away, however. Each gunshot and performed effect must be carefully organized and analyzed, then edited for game audio and feature film professionals.

How does Pole Position Production edit gun sound effects? Sound designer Robin Olsson has mastered most of Pole’s gun sound libraries. In today’s post, Robin shares a step-by-step guide to teach you how to edit gun sounds yourself. Let’s learn more.

Recording Indoor Gun Sounds

When the recording team returned to the Pole edit suites with the indoor gun recordings, they handed off a huge amount of content to Robin.

The Pole team recorded 6 firearms at an interior soundstage (learn more about that here). There were five different room locations: a living room, toilet, corridor, warehouse, and large hall. Firearms ranging from handguns, shotguns, submachine guns, and assault rifles were used to provide a diverse mix of gunshot sounds.

Up to 20 microphones and 44 channels of recordings captured the gunshots with mono, stereo, surround, and Ambisonic microphones, each tracked to multiple dedicated and portable recorders.

The result? Hundreds of gigabytes of audio spread across multiple tracks of gunshot and performed effect recordings. Here’s how Robin broke down the work:

  1. Session set-up
  2. Editing pass 1: trimming
  3. Editing pass 2: grouping
  4. Editing pass 3: processing
  5. Naming and exporting

Let’s look at each step in detail. At the end of the post, Robin will share some pro tips to help you master and edit gun sound effects for yourself.

1. Session Set Up

Session Organization

The team had recorded in 5 different rooms. Each recording was separated by location, then added to a different Pro Tools session, one for each room.

Track Identification

Very little information appears when the tracks are first added to a session. They appear simply as rows of waveforms. To find out which microphone was assigned to each track, Robin listened to the slates or audio identification spoken by the recordists at the beginning of each session or between takes.

However, recording guns is difficult and fast-paced. It’s easy to miss these details. Often there was no time to provide comprehensive info about microphone, recorder, or position. So, Robin consulted session photos and with the recordists that were present on location to find out details of the positioning and room size. The information was added to the session:

  • Track names: room type, distance, position (ex. behind door), stereo technique, and microphone name
  • Track comments: recorder names and additional positional information (ex. In Kitchen, off-axis)
  • Markers: notes describing what was being recorded at that time (ex. Glock 17 9mm)

Synchronizing gun sounds

The next step was to synchronize each track with each other. Why?

Well, the team had recorded up to 44 channels of audio with 11 recorders. Of course, not every recorder began capturing audio at the same time – some began sooner, and some many minutes later. So, the recordings needed to be aligned in tandem with each other to master the correct performances.

Normally this is done by consulting to the slates, then arranging them in tandem visually, or with software shortcuts. Pole works with these multitrack sessions frequently and runs into this challenge often, and has a tool to make the job easier. To help with this, the main recorders were synchronized with a hardware NanoLockit during the recording session. This allowed Robin to use Pro Tool’s “spot” function to move the recorded clips within the timeline, instantly snapping them into alignment.

Handheld recorders such as the Sony PCM-D100, Zoom H3-VR, Sony PCM-M10 and others aren’t compatible with the NanoLockit. So, Robin aligned these to the other tracks using a script to snap them into place.

True Alignment vs. Time Delay

The original recording session placed microphones at distances ranging from 1 meter to 30 meters distant or farther. Naturally, it takes time for sound to travel to farther microphones, creating a delay or offset. So, while the close gunshot will be captured by the microphones immediately, farther microphones may record the sound hundreds of milliseconds later. The gunshots will appear rippled in the session, and have a cascading sound of the blast occurring one sightly after the other.

It’s up to an editor’s taste whether to keep this natural delay, or to artificially align the clips at the same time. For this library, Robin chose the later, synchronizing all gunshots at the same time, irrespective of distance. This is often the best choice when creating sound libraries, as it makes the clips easier to use.

Want to calculate the time delay by distance instead? Do you know the distance a microphone is from the sound source? If so, use this speed of sound calculator. The result will show you how many milliseconds you need to offset your distant gunshot from one closest to the blast.

Track Order

With the tracks in tandem, Robin organized them in the session from top to bottom by recorder and distance. So, all tracks from a Sound Devices MixPre-10 II recorder would be grouped together, with close microphones at the top of this sub group, and distant microphones below.

Each of these was organized in a Pro Tools group or Reaper track stack folder labelled with the recorder name.

Converting to Reaper

With the sessions initially prepared, Robin converted the Pro Tools sessions to Reaper projects using AA Translator. For these kind of sessions, Reaper has much more freedom and flexibly than Pro Tools. For instance, Pro Tools only allows one session to be open at a time. Reaper can open many projects side-by-side, an invaluable feature that allows comparing recordings from each of the 5 recording locations with one another. This helped ensure track names, organization, and more were consistent between the locations.

2. Editing Pass 1 – Trimming

The sessions were organized and ready to cut. The next step was to listen to the recordings.

Gunshots are loud. However, the most important part of a gunshot recording isn’t the initial blast but the character in the tails that fade out after the shot. Robin used a -15 dB FabFilter L2 limiter when auditioning. This dynamically increased the volume of the tails to ensure every flaw could be found. It also placed a hard ceiling of the volume of the initial blast to protect his ears.

Trim Pass

As a first pass, Robin trimmed out audio between the gunshot takes. This included empty audio while the crew set up the guns, flaws such as movement or intrusive ambient sounds, and so on. The trimming ensured the shots preserved the valuable, long tails that were essential for sonic character, as well as reference material for noise removal processing, later.

All verbal slates before and after the gunshots were noted in track names, track comments, or timeline markers.

Robin also dropped markers with processing notes while listening, noting timeline flaws (ex. background speech) or track-based flaws (ex. excessive recorder noise).

Broad editing decisions were made at this stage, too:

  • Distorted takes were removed. Often this occured when a microphone couldn’t handle the sound pressure level (SPL) of the gunshots.
  • Overlapping background errors: talking, activity, movement, or shells missing the padding and dropping on the ground.

3. Editing Pass 2: Grouping

With all the unwanted audio removed, the next step was to group similar sounds together.

The trimmed takes were spread out across the timeline. Why?

Well, each weapon and location recorded multiple shots, often with reloading or pausing in between takes. So, all single shots were collected together inserting 300 milliseconds of space between them with the Xenakois/SWS Reaper command Reposition selected items…. (In Pro Tools: Edit/Space clips….) Each track was then normalized to -1 dB.

The same was done for the short bursts, as well as the long bursts. All performed effects of reloading, handling, and so on were grouped together apart from the gunshots at the end of the timeline.

4. Editing Pass 3: Processing

With all the audio organized, the next step was to use processing to remove any flaws from the tracks heard in the tails of each gunshot.

  • Shell drops – sometimes shells dropping and rattling on the floor overlapped the long tails
  • Digital clicks – incidental ticks and pop from microphone and recorders
  • Voices – often guests would forget that recording had commenced and would chat in the distance
  • Movement – It’s often difficult for non-professionals to understand the importance of staying completely still. So, all foot shuffles, key rattles, and movement needed to be removed
  • Noise – both microphone and recorder circuitry add noise to a recording. Portable recorders in particular add a lot of noise. Sometimes the room or distance contributed noise as well. Any excessive noise needed to be removed

In most cases iZotope’s RX sound restoration software repaired these errors. The spectral repair or gain tool removed unwanted sounds. The de-click module eliminated the digital pops. A combination of software attacked the noise: Waves C4 Multiband compressor provided a non-intrusive first pass without the “pouring water” sound of aliasing, which was then supplemented by RX’s de-noise module, followed up with another C4 pass if needed.

Processing was the most time-intensive step. The tail for every track needed to be listened to separately, and processed if needed.

5. Naming and Exporting

With the editing and processing completed, all that remained was naming the tracks and exporting the final files.

Each take was selected as a Reaper region (not forgetting 300ms inserted at the end to ensure all shots had equal length). The region was named describing the weapon, its performance, location, and shot type:

Glock 17 9mm – FIRING – Small Living Room – Single Shots

This was supplemented with the track name, created in step 1 above, which included the distance, stereo microphone arrangement, and microphone:

10m In Front – XY – MKH8040

Finally the regions were selected and rendered. Using Reaper’s wildcard naming system, the track name was added to the region name, resulting with the final name:

Glock 17 9mm – FIRING – Small Living Room – Single Shots – 10m In Front – XY – MKH8040

What’s next?

It’s often helpful to re-import the finished files back into a new session; this often catches small errors missed during the dense editing work.

And that’s it! All files have been cut, trimmed, organized, processed, and exported. They’re now ready to add even more descriptive text to the files with embedded metadata.

Gun Sound Effects Editing Tips

Robin has edited dozens of guns from many different recording sessions. Here are his pro tips that will help you edit gun sound effects:

  • During a multi-weapon or multi-location shoot, finish editing one gun or location first before working on the rest. You’ll spot the errors or characteristics in one track or location, saving time for editing later.
  • Gunshots are LOUD (of course!). Try not to listen to the transient much. Instead, focus on listening to the tails; that’s where most of the character and errors occur.
  • Editing hundreds of gunshots from 20 microphones gets boring fast. It’s important to be patient. Editing guns takes time and requires detail. So slow down and listen closely. Fight the monotony and stay focused.
  • When recording: do your most to reduce intrusive sounds on location – particularly voices. Even a few seconds of noises overlapping the gunshots take hours to remove – if they can be removed at all.
  • Another location tip: slate with as much detail as possible. This helps save guesswork when identifying microphones, positions, and performances.
  • Removing noise is one of the biggest challenges when editing a gun sound library. Uneven noise is the most difficult to remove. It’s important to remove noise cleanly. Do not remove noise too aggressively – you will hear the aliasing in the tails. Instead, use non-intrusive noise reduction with C4, make small incisions with the gain tool, and so on.

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