A wave is produced in a rope. The wave has a speed of 33 m/s and a frequency of 22 Hz.

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The density of the block of iron is lees than the density of mercury but the density of the block of iron is greater than the density of water

Sounds propagates through some kind of medium. usually it's air, but it goes just as well through solid objects like walls, windows etc. a soundwave will compress the (air)molecules in front of it, and if this increased density wave hits your ears, you register it as sound. solid objects like walls are a lot denser than air, this means that they will damp a wave, but also carry it easier.