Particles are the medium through which waves travel. More particles on screen = denser medium.
Amplitude is the difference between the wave's peaks (highest density) and troughs (lowest density). Larger amplitude = louder sound.
Frequency is how many waves pass by per second (measured in Hz) - we hear this as pitch. Higher frequency = higher pitch and shorter wavelengths (waves closer together).
Speed is how fast waves travel through the medium. In any given medium, sound waves travel at a fixed speed. For example, in air at 20°C sound travels at ~343 m/s.