In solids, both pressure waves and compressional waves are essentially the same thing, as they refer to the propagation of longitudinal waves through the material. In this context, the speed of propagation depends on the mechanical properties of the material, such as its density, elasticity, and compressibility.
Generally, compressional waves in solids, such as seismic waves during an earthquake, tend to travel faster than in gases, liquids, or air. Solids have a higher density and are more rigid, allowing the waves to propagate more quickly through the material.
In gases, liquids, and air, compressional waves are often referred to as "pressure waves" or "sound waves." In these mediums, the speed of sound depends on the properties of the specific medium. In general, sound travels faster in solids than in liquids, and faster in liquids than in gases. This is due to the differences in density and elasticity of these materials.
To provide some approximate values, the speed of sound in air at room temperature is about 343 meters per second (m/s), in water it is around 1,480 m/s, and in typical solids like steel, it can be around 5,000 to 6,000 m/s. These values can vary depending on various factors such as temperature, pressure, and composition of the medium.
It's important to note that these are general trends, and specific materials can have different speeds of propagation depending on their properties.