The propagation velocity of air is approximately _____ m/sec?

The propagation velocity of sound in air at 20 degrees Celsius is approximately 343 meters per second. This velocity can vary slightly with temperature, humidity, and pressure, but it generally hovers around that mark. The option citing 331 meters per second is closely related to the velocity of sound in air at 0 degrees Celsius, which is also a valid reference point in certain contexts.

In acoustic applications, it's crucial to understand the speed of sound in different media because it impacts how sound waves travel and are perceived in various environments. Sound travels significantly faster in liquids and solids compared to gases, due to the differences in density and elasticity of these materials.

The other options range higher than the typical values for air: the figure of 1280 meters per second generally pertains to sound in certain solids, such as in metals; 340 meters per second is quite near the standard speed in air at room temperature but does not reflect the direct reference at 0 degrees Celsius; and 1500 meters per second is around the speed of sound in water, a very different medium. Thus, the choice of 331 meters per second is accurate for the context discussed regarding air.