Do gravitational waves diminish over time/distance? Just wondered how they compare to sound waves, naturally they travel at the speed of light, but I was wondering if they diminish over time like sounds waves. Cheers.
 A: Classical waves from point sources disperse as $1/r^2$ . Sound waves and water waves are energy transfers in a medium  and at some distance from the source  there is not enough energy to move the medium and there is no wave.
Electromagnetic waves are built up by zillions  of elementary particles, called photons, which even when the distance is so large that no longer classical light can be built, remain as individual photons unless they interact with matter.
In an effective quantization of gravity, the gravitons have the role in gravity corresponding to the role of the photons in electromagnetism, so even when the distance from the source is enormous so that no classical wave can be built up, they will exist as elementary particles until they interact with some other particle or radiation.
Extended sources can be considered to be built up by point sources, so at some distance will be acting like point sources ( as far away stars for light).
A: If you stand in an open field and clap your hands, the sound spreads out as a spherical wave. As the wave expands at the speed of sound, the energy is diluted over a larger and larger surface area. Since the surface area of a sphere is proportional to the square of its radius, the intensity of the sound falls off like $1/r^2$.
Exactly the same logic applies to gravitational waves.
Sound waves can also interact with objects and be absorbed, transforming their energy into vibration of the objects, which then is transformed by internal friction into heat. Although this does in principle happen when gravitational waves interact with matter, the effect is extremely weak. Matter is nearly perfectly transparent to gravitational waves. This is why they're so hard to detect.
