A bullet passes past a person at a speed of `220 m s^-1`. Find the fractional change in the frequency of the whistling sound heard by the person as the bullet crosses the person. Speed of sound in air `= 330 m s^-1`.

Explanation

To solve the problem, we will use the concept of the Doppler effect, which describes how the frequency of a wave changes for an observer moving relative to the source of the wave.

### Step-by-Step Solution:

1. **Identify the Given Values:**
- Speed of the bullet (source) \( v_s = 220 \, \text{m/s} \)
- Speed of sound in air \( v = 330 \, \text{m/s} \)
- Original frequency of the sound \( f_0 \) (unknown)
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