Supersonic Bullets Recording

In late November 2022, our Audio Team, along with a handful of helpful Bohemians, visited the largest shooting range in the Czech Republic. The name of it is Placy Shooting Range, and it is located near the city of Příbram. Our Audio Team traveled there to record a unique and extensive sample pack of a physical phenomenon called supersonic crack.

The view towards the shooting position from the back wall of the 500m mark.

What is a supersonic crack?

When a projectile flies with supersonic speed (i.e. faster than the speed of sound), it creates a shockwave behind itself in the shape of a cone. When the shockwave passes your ears, you hear a loud and sharp sound, similar to a cracking whip or a shot from a small caliber pistol.

But what exactly did we want to record? Simply put: all the possible variations of cracks we could get. From what we learned, the change in sound is mainly influenced by the size of the projectile, as well as the speed and distance of the listener/microphone from the source of the sound.

How did we record it?

One key to the recording process is microphone distances. We wanted to capture a variety of cracks, both from close range and farther distances.

  • Relative microphone positions: How do we orient each microphone? Perpendicular to the shock wave cone’s border was making the most sense for us.
  • Proper microphone types in the right places: The sound will be louder the closer the microphone is placed to the passing projectile. When it comes to longer distances, we can place more sensitive microphones to get the results we’re after, as well as more ambient reflections of the respective sound..

Mic check!

Cover your ears! ...and BANG!

What to look out for?

  • Natural ambiance - animals, insects, even intense tree rustling. When are all of these things silent? During the winter. Considering preparation began at the end of winter in 2021, that meant we waited about a year until the right time presented itself.
  • The shooting itself - The impact of the bullet when it hits the target. We didn´t want the shot sound, and we didn´t want the bullet impact either, as both would muddy the crack we were seeking, which we needed to be crystal clear. There wasn’t much use in waiting a year for birds to leave only to impair the sounds we wanted.

    • The chosen guns were: Scorpion EVO, BCM REECE-16, CZ 600 Range, and Bushmaster BA50.
    • Shot sound reduction was done by involving suppressors for all caliber: 9mm, .223, .308, and 50Cal.
    • Bullet impact sounds were omitted by proper microphone placement which considered the location of impact. The situation was handled by the shooter, who knew about the issue and therefore aimed at the most distant place possible.

In the end, it took us two days and 33 microphone positions to capture the perfect recordings. We learned a lot and came away with hundreds of sounds. Thanks to this amazing experience, we´re going to make Arma Reforger's audio richer, more unique, more believable, and more immersive than ever before.

If you found this article interesting and would like a similar position, be sure to check out our careers page. We are currently looking for a Senior Sound Designer to join our Audio Team.
Published on by Bohemia Interactive