# Warm-Up Exercise for lecture 26

## Due 8:00 am, Thurs, 3 Dec 09

Physics 105, Fall 2009

What happens when two pulses on a string (one coming from each end) meet in the middle?
The pulses pass through each other
The pulses reflect off of each other

If a loudspeaker emits spherical sound waves in all directions, what decreases as you go farther away from the loudspeaker?
frequency
intensity
wavelength

You go to a rock concert where the sound level where you are standing is 110 dB. How does the intensity (power/area) of sound waves compare to when you listen to the same music on your home stereo system, 90 dB at the spot you sit?
Concert intensity = Stereo intensity
Concert intensity = 1.20x stereo intensity
Concert intensity = 2x stereo intensity
Concert intensity = 10x stereo intensity
Concert intensity = 20x stereo intensity
Concert intensity = 100x stereo intensity

Ralph is confused about Table 14.2 (8th edition), where the book lists different intensity levels for different sources. For example, the table says a vacuum cleaner has an intensity of 70 dB. What confuses Ralph, is that it seems like a vacuum cleaner should sound louder to someone who is pushing the vacuum cleaner than to someone who is a little farther away. How can the intensity level be 70 dB for both people? How should you answer Ralph's question?