18. Waves & Sound

One cue your hearing system uses to localize a sound (i.e., to tell where a sound is coming from) is the slight difference in the arrival times of the sound at your ears. Your ears are spaced approximately 20 cm apart. Consider a sound source 5.0 m from the center of your head along a line 45° to your right. What is the difference in arrival times? Give your answer in microseconds. Hint: You are looking for the difference between two numbers that are nearly the same. What does this near equality imply about the necessary precision during intermediate stages of the calculation?

$\text{Which of the following is an example of a longitudinal wave?}$

Which of the following examples contains only longitudinal waves?

High frequency sounds primarily vibrate which of the following parts of the ear?

Two solid rods have the same bulk modulus but one is 2.1 times as dense as the other. In which rod will the speed of longitudinal waves be greater, and by what factor?

In which direction do longitudinal waves transfer energy relative to the direction of wave motion?

Which of the following best describes the difference between longitudinal and transverse waves?

A sound wave travels through water. What best describes the direction of motion of the water particles relative to the direction of wave propagation?

Which of the following is an example of a longitudinal wave?

A motion sensor can accurately measure the distance d to an object repeatedly via the sonar technique used in Example 16–2. A short ultrasonic pulse is emitted and reflects from any objects it encounters, creating echo pulses upon their arrival back at the sensor. The sensor measures the time interval t between the emission of the original pulse and the arrival of the first echo.To measure an object’s speed the motion sensor makes 15 distance measurements every second (that is, it emits 15 sound pulses per second at evenly spaced time intervals), the measurement of t must be completed within the time interval between the emissions of successive pulses. What is the largest distance (at 20°C) that can be measured with the motion sensor?

What is the speed of sound in air (a) on a cold winter day in Minnesota when the temperature is -25°F, and (b) on a hot summer day in Death Valley when the temperature is 125°F?

P and S waves from an earthquake travel at different speeds, and this difference helps locate the earthquake “epicenter” (where the slippage took place). Assuming typical speeds of 8.5 km/s and 5.5 km/s for P and S waves, respectively, how far away did the earthquake occur if a particular seismic station detects the arrival of these two types of waves 1.5 min apart?