Bertrand’s work will give sound to everything we see in the film: the steps, the sound of the clothes, the objects moving… In order to do so, he uses a bunch of objects that will create the appropriate sounds.
To record the sounds, Bertrand stands in front of a screen with the film on it and creates the sounds depending on the actions he sees. If he sees a character walking on the screen, he synchronizes his steps with the animation.
For the steps, he watches the way each character walks, their rhythm, the shoes they’re using etc… For example, for The Grey One, Bertrand used old shoes:
For the little mice, he patted the ground with latex gloves.
Sometimes Bertrand combines different objects together to make a sound. So, to make fire sounds he used a straw broom, and he made crackling noise by touching the bristles.
Then he shook a cloth.
And finally he blew on the mic to make a rumbling noise.
And that’s how he obtained the noise of a fire.
Sometimes some sounds are made by two very different objects used together. They can create really unexpected sounds.
Usually, the last recording day is used to make breaking noises. It is the happiest day of the sound design sessions.
You should have a look to a scene of the film with only the sound design. You will be able to consider the amount of work in the sound design. After these sounds were made, we still needed to add atmospheric sounds and sounds Bertrand couldn’t make with objects. The final step was the mixing part where the sounds were placed in space.