So the sun and the stars are just like in our own universe, it is the atmosphere of the planet that converts the light into sound. Or is it some sort of layer above the atmosphere that convert the ligth? Or is it fantasy and therefore a magic spell that wraps the whole world like a blanket? You're not mentioning the mechanism here.
Whatever it is, the process needs to reflect some of the energy to prevent the world from becoming too hot, judging by some of the other replies here. What about hot objects? They radiate infrared light.
If it is the whole atmosphere that is responsible for the conversion, light on the planet is not possible. But if it is only happening high up in the stratosphere or ionosphere, then it should be possible for animals and other organisms to produce their own light. Once organic light and primitive eyes have evolved, there would be an arms race, and there would probably be creatures with huge eyes communicating with light and even use light to see their environment.
If not, all you have is echolocation and sensitive hairs that gives you an impression of the surroundings. Or if this is fantasy, some sort of sixth sense.
The biggest challenge would be for organisms to convert the sound energy into an energy form they can use. Would it be enough to sustain an ecosystem of advanced and complex organisms? Hard to say. Scientists are experimenting with ways to convert sound into electricity.
Sound is as everybody knows vibrations travelling through matter. How can you harvest these vibrations? You could have organs that convert the vibrations directly into piezoelectricity, which the organism use as an energy source. Dolphins and other toothed whales have a fatty organ called the melon that is used as a lens to focus sound. Perhaps that would work here as well.
Other organisms could make use acoustic resonance, where the sound is amplified and turned into mechanical movements, setting large membranes into movement that convert the motion into electricity. Huge gas filled structures or "blankets" stretched over an area. This could be a living organism, or it could be created by small animals that excrete the material they use to build them (if termites can build complex mounds and spiders intricate webs, why can't other small social creatures with limited intelligence build something that can harvest sound in a world defined by it?).
Then natural selection would take care of rest. The most efficient textures, sizes and adjustments would extract more energy from sound than others.
Today the trees in a forest are competing for the light, which is why they are as tall and wide as possible. Others are epiphytes. In water with floating plants height is no longer the issue.
In this world, "plants" or similar organisms harvesting energy from sound would compete for the best places which can provide them with the right amount of sound they need to survive and thrive. Different organisms could be adapted to different sounds on the logarithmic scale to avoid competition.
But what is biological possible, and what is evolutionary possible, is not always the same thing.
If the sound convertion is an anaerobic process, there would be little to no oxygen in the atmosphere, and animals would be anaerobic too. According to this article, complex life without oxygen doesn't sound impossible:
"It is often stated or assumed that O2 improves the energetics of the cell and that O2 thus might have impacted the origin of mitochondria, but life in O2 is thermodynamically thirteen times more expensive than life without O2, because O2 tends to oxidize things, including the chemical substance of cells."
Mitochondria enable cells to produce 15 times more ATP than they could otherwise, but if aerobic metabolism is 13 times higher than metabolism without oxygen, the difference shouldn't be that huge.