Sound waves are created by vibrations that travel through a medium, like air, water, or solid objects. These vibrations cause alternating regions of high and low pressure, which we perceive as sound. 

Compression and Rarefaction: Imagine a slinky. If you push one end of it, you create a series of compressions and rarefactions that move through the slinky. Sound waves work in a similar way. When an object vibrates, it pushes air molecules together in some regions (compression) and pulls them apart in others (rarefaction). These alternating high-pressure (compression) and low-pressure (rarefaction) regions travel through the air as sound waves.

Air Molecules in Motion: During compression, air molecules are packed closely together, increasing the air pressure. During rarefaction, molecules are spread apart, decreasing the air pressure. This fluctuation in pressure is what travels through the air to your ears, allowing you to hear sounds.

Sound pressure is measured in units called pascals (Pa). However, because the changes in pressure caused by sound waves are usually very small, we often use a unit called decibels (dB) to describe sound pressure levels. Decibels are a logarithmic scale, which means even small increases in dB represent significant increases in sound pressure. 

1. Thunderstorms: Thunder is a great example of high sound pressure. The rapid expansion of air caused by lightning creates a shock wave, resulting in the booming sound of thunder. The sudden change in air pressure is what makes thunder so loud.

2. Concerts: At a concert, especially near the speakers, you can feel the sound waves. The high sound pressure levels make the bass notes thump in your chest. This is the result of powerful amplifiers creating large pressure changes in the air.

3. Whispering vs. Shouting: When you whisper, you create small pressure changes, resulting in a quiet sound. When you shout, you create much larger pressure changes, resulting in a loud sound. The difference in pressure changes is what makes one sound louder than the other.

Here’s a fun experiment to observe sound pressure in action:

1. Balloon Pop: Blow up a balloon and hold it close to your ear. Pop the balloon and listen to the loud sound it makes. The sudden release of air creates a shock wave with high sound pressure, resulting in the loud bang.

2. Sound Waves and Candles: Light a candle and place it a few feet away from a speaker. Play a song with a lot of bass. Watch as the flame flickers in response to the sound waves. The pressure changes created by the sound waves from the speaker cause the flame to move.

The Science Behind It 

The pressure variations in sound waves are a type of longitudinal wave, where the displacement of the medium (air, in most cases) is in the same direction as the wave's travel. This is different from transverse waves, like water waves, where the displacement is perpendicular to the direction of travel.