Here is a good visualization of how the sound propagates in wavelengths using a string. This is really a string resonance phenomenon but it can be used to visualize what happens to sound in a room depending on dimensions/frequency. Notice how the string "amplitude" spikes in the left side of the string vs the right in this video. This is what happens when the sound interacts with the room modes and gets "excited" as well.
https://youtu.be/oZ38Y0K8e-Y