Problem

A car traveling at 25 m/s honks its horn as it directly approaches the side of a large bui...

A car traveling at 25 m/s honks its horn as it directly approaches the side of a large building. The horn produces a long sustained note of frequency f0 = 230 Hz. The sound is reflected off the building back to the car's driver. The sound wave from the original note and that reflected off the building combine to create a beat frequency. What is the beat frequency that the driver hears (which tells him that he had better hit the brakes!)?

Step-by-Step Solution

Solution 1

Step #1 of 5

THINK:

The car is considered to be a moving source with speed emitting with frequency. The frequency of the car at the building can be calculated using the sound velocity of . Building reflects the sound back towards the moving car. The car driver can be thought of as a moving observer of the reflected sound. Combining two Doppler shifts gives the frequency of the reflected sound. Hence, beats frequency

Step #2 of 5

RESEARCH:

The frequency of the sound measured by a stationary observer standing at the building resulting from the sound of frequencyemitted by the car moving with speedis given by equation,