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+--- Thread: The Speed of Sound — How Fast Is It Really? (/showthread.php?tid=405)
The Speed of Sound — How Fast Is It Really? - Leejohnston - 01-08-2026
## The Speed of Sound — How Fast Is It Really?
### 1. The Equation
The basic relationship is:
Speed = Distance ÷ Time
For sound in air (at room temperature):
v ≈ 343 m/s
---
### 2. What Each Symbol Means
- v = speed of sound (metres per second)
- m = metres
- s = seconds
This value assumes:
- dry air
- about 20°C
- normal atmospheric pressure
---
### 3. What the Equation Is Telling Us
Sound is not instantaneous.
It travels as a **pressure wave**, pushing energy through air molecule by molecule.
That process has a maximum speed.
---
### 4. Where It Comes From (Intuition)
Sound speed depends on:
- how stiff the medium is
- how dense it is
Air is light and compressible → moderate sound speed
Solids are stiff → sound travels much faster in them
---
### 5. Worked Example
**How far does sound travel in 1 hour?**
1 hour = 3600 seconds
Distance = speed × time
= 343 × 3600
≈ 1,234,800 metres
≈ **1,235 km**
That’s roughly the distance from:
London → southern France
---
### 6. Real-World Applications
- Thunder delay after lightning
- Sonic booms
- Aircraft design
- Acoustics and audio engineering
---
### 7. Common Misconceptions
- Sound does **not** travel at the same speed in all materials
- Sound speed is **not** affected by loudness
- Sound cannot travel in a vacuum
---
### Try It Yourself
How long would it take sound to travel:
- 1 km?
- across your town?
- from a nearby storm?