Think & Solve Problems Chapter 26

1. Think & Solve ProblemsChapter 26 April 24, 2014

2. T & S #1 • Speed of Sound Waves (V): 340 m/s • Frequency of Lowest Note most people can hear (f1): 20 Hz. What is its wavelength? • What is the wavelength of a sound with a frequency (f2) of 20 KHz, the highest frequency most people can hear?

3. T & S #1 Solution • Part 1 • V = f °λ • λ = V / f • λ = 340 / 20 = 17 meters • Part 2 λ = 340/20,000 Λ = .017 meters or 1.7 cm

4. T & S #2 • You have a desire to produce a sound with a wavelength (λ ) of 1 meter. • What must its frequency (f) be? • V = f °λ • f = V/λ • = 340m/s/1m = 340 1/s or 340 Hz.

5. T & S #4 • Two sounds, one at 240 Hz (f1), the second at 243 Hz (f2) occur at the same time. What beat frequency do you hear? • Fb = f2 –f1 = 243 – 240 = 3 Hz.

6. T & S #5 • Two notes are sounding at the same time. • One note has a frequency (f1) of 440 Hz. • The BEAT Frequency (Fb) between the two is 5Hz. • What can the other notes frequency be? • F2 = Fb +/- F1 = 440 + 5 or 440 -5 = 445 Hz or 435 Hz

7. T & S #3 • An Ocean depth Sounding Vessel is surveying the ocean floor. • The velocity of sound in this part of the ocean travels at 1530 m/s. • What is the depth of the ocean if it takes the echo 8 seconds to travel from the vessel to the ocean floor and back to the vessel? • t = 8 /2 = 4 sec for echo to travel from ocean floor back to vessel • d = v ° t = 1530 m/s ° 4 sec = 6130 meters or ~3 miles