8 The fundamental frequency in an open pipe is 220 Hz. (a) Determine the frequency of the first 3 harmonics. (b) The pipe is now closed at one end. Repeat part (a). [220 Hz, 440 Hz, 660 Hz] [110 Hz, -, 330 Hz] 9 The frequency of the third harmonic of an open pipe is 900 Hz. What is the length of the pipe? [0.572 m] 10 A closed organ pipe of length 0.750 m is played when the speed of sound in air is 340 m/s. What is the fundamental frequency? [113 Hz] 11 Your parents are playing their awful music (which is just a pure tone of 800 Hz on adjacent stereo speakers) right in front of you very loudly while you are trying to study for your Waves Test. How much farther back should you move one speaker so that you hear no sound and can focus on studying? [0.21 m] 12 While tuning your guitar, you notice a beat that occurs 20 times per second. If the tuning fork has a frequency of 350 Hz, what is the frequency of the guitar? [370 Hz or 330 Hz] 13 Due to the stress caused by the upcoming Waves Test, you are experiencing a reoccurring nightmare in which you are being chased by a phantom train. The train sounds its horn and gives off a pitch of 500 Hz. The train then starts moving toward you at 35.0 m/s. In a desperate attempt to outrun the train, you run away from it as fast as you can at 25.0 m/s. What frequency will you hear now? (Note: you wake up before the train overtakes you.) [516 Hz] 14 You have always wanted to be a dolphin. To live your dream, you decide to act like a dolphin, by living in the water and navigating via echolocation. You notice a blurry object in the depths below, and want to figure out how fast the object is moving. To do this, you yell at the top of your lungs at a frequency of 18.9 kHz. You then hear your voice a short time later but at a frequency of 19.1 kHz. Assume the speed of sound in water is 1500 m/s. How fast is the object moving? Assume you are at rest. [7.9 m/s]