Sound waves are indeed a form of pressure waves. When an object vibrates or oscillates, it creates disturbances in the surrounding medium (such as air, water, or solids). These disturbances cause the particles of the medium to compress and rarefy, leading to changes in pressure. These variations in pressure propagate through the medium as waves, known as sound waves.
To understand this better, consider a speaker. When an electrical signal is applied to the speaker, it causes a diaphragm or cone to vibrate back and forth rapidly. This motion creates compressions and rarefactions in the surrounding air. During the compression phase, the air molecules are pushed closer together, resulting in an increase in pressure. In the rarefaction phase, the air molecules spread out, causing a decrease in pressure. This pattern of alternating high and low pressure regions propagates away from the speaker as a sound wave.
Conversely, it is not accurate to say that high pressure always creates sound waves. While it is true that sound waves are associated with pressure variations, not all pressure variations necessarily produce audible sound waves. For sound waves to be perceived as sound, they need to fall within the audible range for human hearing, typically between 20 Hz and 20,000 Hz. High-pressure variations alone may not generate sound if they do not occur at frequencies within this range.
Furthermore, sound waves require a medium to propagate, such as air, water, or solids. In a vacuum where there is no medium, sound cannot propagate, regardless of the pressure. So, while pressure variations are an essential component of sound waves, the presence of a medium and the appropriate frequency range are also necessary for the perception of sound.