“They’re just tennis balls cut in half and eco-dyed,” says Mathilde Wittock, who painstakingly collected old balls from local clubs. Halved with an ingenious S-cut, these are slotted into plywood, for a softly textured sound-absorbing screen appropriately called SoundBounce – and you can see it at Grand Designs. Mathilde is working on making her project “opensource” so that her idea can be shared by communities across the world. (And apparently there are not a lot of other uses for redundant bounce-less balls…)