Know that the speed of sound in air is approximately 330-350 m/s

3.4 Sound 🎧

Objective

Know that the speed of sound in air is approximately 330–350 m s^-1.

What is Sound?

Sound is a vibration that travels through a medium (like air) as a wave. Think of it as a ripple in a pond, but instead of water, it's pressure changes in the air.

How Fast Does Sound Travel?

In dry air at 20 °C, the speed is about 343 m s^-1. The general range is 330–350 m s^-1.

The formula is:

$v = \sqrt{\dfrac{B}{\rho}}$

where $B$ is the bulk modulus of the air and $\rho$ is its density.

Why Does It Matter?

• Understanding speed helps in acoustic design (concert halls, headphones).
• Helps explain why we hear a shout before seeing the shouter's face.
• Important for sonar and ultrasound technology.

Quick Test

1. What is the approximate speed of sound in air? Answer: 330–350 m s^-1.
2. Why does sound travel faster in warm air? Answer: Warm air has lower density, so $v$ increases.

Fun Fact

If you shout at a 100 m distance, you hear it about 0.3 seconds later. That's like waiting for a pizza delivery! 🍕

Table: Speed of Sound in Different Conditions