Today here is an article from our Sound Designer Miroslaw!!  :)
The sound effects described below will be integrated in the next build version. Enjoy ;)

Thunderstorm SFX with Random Thunders (UE4)

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Task:

• Create environmental ambience SFX for Thunderstorm Weather.

Obstacles:

• No rain in the scene
• A limited number of thunderstorm recordings
• Thunders occur randomly in the Skybox - no control over them
• A huge number of lightening in a short time - a rare phenomenon

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Hello! Today I'll describe how I created Thunderstorm Ambience SFX for the game Sons of Ragnar (Demo).

In the beginning, I'd like to mention that initially, I thought that I just had to add one thunder SFX to the scene. Boy, I was so wrong ;)

Weather in the game is changing into oblivion: a thunderstorm with a crazy amount of lightning. Thor seems to be in rage mode! Here comes the first problem for sound designers: lightning is random. I have no control over their appearance so I can't synchronize sound effects with visuals. It's a huge problem, especially for a VR game where immersion is essential. But well... there are things that we can't control, and it's one of them. So I had no choice but to focus on the sound design itself. I checked my sound libraries, but I didn't find any decent recording without rain in the background (or foreground). It's worth mentioning that in the last 7 years I spent in Scotland where storms occur once per year. Exactly once per year. And it's often a feeble and short one. Recording storms and thunderstorms in Scotland is almost impossible. Did I mention that this thunderstorm doesn't have rain? Yes, it's another obstacle when the budget is limited, and I can't merely buy several huge SFX libraries. I went with free ones which were released for free in celebration of GDC2019 by Sonniss:

https://sonniss.com/gameaudiogdc19/

Also, free Oculus Ambisonic Audio Pack 01 was used here.

Thunder in UE4 Viewport

I tried to make one single Ambisonics loop to get an impression of thunders surrounding the player. Unfortunately, UE4 didn't like the file, and it sounded more like mono than epic surround experience ;) After all, I didn't like the result either.

Ambisonics Loop (not used in the game)

I was looking for solutions, how to create surround sound, and I chose a totally different approach. I decided to use single (mono) thunder hits. Sound design was basic: just EQ and small corrections like volume matching. When files were rendered and imported to UE4, the next step was to create a Blueprint to control them.
I experimented with Play Sound at Location where every SFX is played in a random range of time between 0.5 and 3 seconds. Because in the game lightening is happening even a few times within a 1 second, which is a lot). I had to make another compromise and minimize the number of thunders (voices) that can play at the same time.

Thunders controlled in Blueprint

Location of the sound is based on Player's camera position + randomized XY values to create an impression of every thunder being played somewhere around the Player, no matter where he will go.

Thunder Cue (Nothing fancy here)

Now the second task was to create Heavy Wind. The final file was designed from three different wind recordings, including whistling wind and gusts. Voice number in the game was shrinking because of Thunder SFX, so I went with a single stereo loop. The wind is not that important in the game because it's not that heavy in the game. Thunders play the first violin here.

So the final task was to implement all of this in the game itself. The moment when weather change is controlled by Sequence, so I added there ambient sounds like quiet wind and birds singing and I faded them down, so they don't play during the thunderstorm. The blueprint which is controlling Thunders was added to Sequence to, and at the right moment, BP is activated.

Heavy Wind controlled in Blueprint

Heavy Wind is also controlled by the same blueprint responsible for Thunders SFX. I just added 7 seconds-long Fade In and random starting position.

And that's it. Looks like a piece of cake but it took me almost 2 days to came up with final result:

Thanks for reading ;)

Miroslaw