1. Properties of Sound Waves
MHR 8.2

2. The Speed of Sound
The speed of sound through air depends on the density of air and the temperature
v= Tair
Where v= speed of sound in air measured in m/s
The constant 0.59 accounts for the density of air
Tair is the temperature in 0C
Please note, the units work out to m/s – read MHR pg. 378

3. Problem #1: the speed of sound
Tonight, the temperature outside will be 4 0C. What is the speed of sound in air?
Answer:
v= m/s

4. Problem #2: Find Temperature
If the speed of sound is measured to be 318 m/s, what is the air temperature?
Answer: C

5. Problem #3: Echo
Going back to question #1, if you were hiking in a canyon and shouted, you may hear an echo.
Lets assume you hear the echo 2.8s later.
How far would the canyon wall be?
Answer:
Δ d =466.7 m

6. Mach Number
Mach number: the ratio of the airspeed of an object to the local speed of sound
M = air speed of object/ local speed of sound

7. Problem #4: Mach number
An aircraft is flying 905 km/h in air at a temperature of – C. Calculate the Mach number.
M =
So what does mean???

8. Mach Number: some facts
As an air craft approaches the speed of sound, it catches up to the sound waves.
These waves build up to form a shock wave- also known as the sound barrier at Mach one
The shock wave can cause severe damage to the plane and pilot
Chuck Yeager was the first pilot to break the sound barrier in 1947

9. Image of plane breaking sound barrier

10. Your Turn
MHR pg. 382 # 1-6
MHR pg. 422 # 1,2