Question

In order to waken a sleeping child, the volume on an alarm clock is tripleUnder this new scenario, how much more energy will be striking the child’s ear drums each second?

- twice as much
- three times as much
- approximately 4.8 times as much
- six times as much
- nine times as much

Final Answer

(e)

Solution Video

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This is College Physics Answers with Shaun Dychko. The volume on an alarm clock has tripled and the volume knob controls the pressure amplitude of the sound. And so intensity is the pressure amplitude squared over two times the density of air times the speed of sound in air. And when we have intensity <i>two</i> equaling this new pressure amplitude, we’re told that this new pressure amplitude is going to be three times the old pressure amplitude because it’s tripled. And this pressure amplitude is squared so we can write this as nine times pressure amplitude <i>one</i> squared, divided by two <i>rho v w</i> but this whole thing is <i>I one</i> and so we see that <i>I two</i> is nine times <i>I one</i>. So the answer is e.