Hardness and bounce will play a big role in both comfort and noise transmission in your home. The less 'give' a floor has, the more footsteps will echo and the less forgiving of accidents it will be. Hardness will usually depend on the finish that you choose, while bounce will typically come from things like underlay.
Hard and soft materials
The hardness of a floor surface relates to its shock absorption, and will depend on the materials it consists of. Tile, concrete and stone are very hard surfaces. Carpet is quite soft, and vinyl and wood floorboards stand somewhere towards the middle of the scale. The thickness of the flooring material plays an important role too in perceived hardness – thicker floorboards have a more solid feel underfoot than thinner planks.
Floor surfaces and noise
Sound will usually reflect better on harder surfaces, and can often be overlooked as an important factor when choosing a floor. Long hallways with solid surface flooring will echo and resonate through the whole house, so if this is going to be the main traffic area, it is worth considering using a softer flooring type - or if that’s not an alternative, some noise absorbing solutions like a rug or subfloor insulation.
Bounce and underlay
Bounce is usually something that relates only to flooring types flexible enough to allow some sort of underlay, such as carpet. A good quality carpet needs a good quality underlay to give you the maximum benefit. A poor underlay will make the carpet feel flat and lumpy and will quickly wear out in high traffic areas. It's certainly worth investing in new underlay if your existing material is more than a few years old and you’re replacing the carpet. The three different types of underlay will give varying amounts of bounce, as will different thicknesses. When choosing your underlay, make sure to test it underfoot under the carpet of your choice to see how it feels.