Properties of Sound Waves MHR 8.2

The Speed of Sound The speed of sound through air depends on the density of air and the temperature v= 331 +0.59 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

Problem #1: the speed of sound Today, the temperature outside is 4 0C. What is the speed of sound in air? Answer: v= 333.36 m/s

Problem #2: Find Temperature If the speed of sound is measured to be 318 m/s, what is the air temperature? Answer: -22.1 0C

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

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

Problem #4: Mach number An aircraft is flying 905 km/h in air at a temperature of – 50.0 0C. Calculate the Mach number. M = 0.835 So what does 0.835 mean???

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

Image of plane breaking sound barrier

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