Sound

Step 1: Analyzing Statement (i).
Sound pressure refers to the local pressure deviation from the ambient atmospheric pressure caused by a sound wave. As the sound wave travels away from the source, the energy spreads out and the pressure amplitude generally decreases. So, statement (i) is correct.

Step 2: Analyzing Statement (ii).
Sound power is the total amount of energy emitted by a source per unit time and is independent of the environment. It is an intrinsic property of the source. Thus, statement (ii) is correct.

Step 3: Analyzing Statement (iii).
Sound intensity is defined as the sound power per unit area (not volume). It quantifies the power that passes through a certain area perpendicular to the direction of the wave. Therefore, statement (iii) is incorrect.

Hence, only statements (i) and (ii) are correct.