Do soundwaves produce heat? Sound dies down after a while. The energy emmited by the speakers must go somewhere. Where does it dissipate this energy? Is it in heat? Theoretically, if i play music in a room, would it get hotter in the room?
 A: The sound wave energy is dissipated by viscous dissipation in the room air.  This increases the temperature of the room air, but only extremely slightly.  There just isn't enough energy of the sound waves in air to do much more.
A: I'll approach your question differently. Sound Can be used to produce heat. An example of this is sonoluminiscence. This is basically luminiscence that is produced when a  gaseous bubble in a liquid is popped using high intensity sound. This produces a phenomenon known as thermodynamic cavitation. Liquids being almost incompressible, release a large amount of energy, when they rush in to fill the gap produced by the popping bubble. This produces short bursts of light for 35-100 picoseconds long. Experiments indicate that temperature of the immediate surrounding water reaches as high as 2300 to 5100 K, for short periods. Hope this helps. Here is a link for further reference : sonoluminiscence
A: Sound can also produce localised heating.  
It is one of the sources of non-linearity in underwater (and air) acoustics.  Sound can be thought of as a 'train' of high and low pressure regions. Since PV/T is a constant and the Volume is also generally constant then in the high pressure regions the temperature is increased - and so is the speed of sound.  This means that the high pressure regions travel faster and a sine wave slowly turns into a triangular (sawtooth) wave.
Overall though, I doubt this mechanism would produce a net increase in room temperature.
A: This is an old question but I came across it when looking for answers of a question of my own and I thought I could add a couple things.

Sound dies down after a while. The energy emitted by the speakers must go somewhere.

One thing to keep in mind is that a point source of sound like from a speaker will be susceptible to the $1/r^2$ law in the sense that as the wave expands it has to distribute its energy over an ever-larger area. This sort of decay will cause the sound to "die down" without actually losing energy.

Theoretically, if i play music in a room, would it get hotter in the room?

As other answers have pointed out, the dissipation of sound waves will eventually result in a tiny amount of heat but I want to expand on that. First, sound waves are nearly isentropic so the material will approximately return to the state it was in before the sound wave passed through it. This means that only a tiny amount of the energy will actually go into heating the room. If your speakers have a specific wattage though, most of that energy goes into the friction of moving the driver and electrical losses in the magnets rather than the sound itself.
As an aside, sound absorbing materials work by either being so soft that they can be deformed by the sound waves or by creating air pockets so small that the viscous effects of the air are significant enough to damp the sound wave. Since air does a pretty decent job of propagating sound waves, it's more likely that the insulation in your walls will be where the heat is going, but again it's going to be infinitesimally small.
