To increase loudness of sound ...... of vibration of sound.

Options

A. decrease its frequency
B. increase its frequency
C. decrease its amplitude
D. increase its amplitude

Explanation

To increase the loudness of sound, we need to focus on the amplitude of the sound waves. Here’s a step-by-step breakdown of the solution:

### Step-by-Step Solution:

1. **Understanding Loudness**: Loudness is the perception of the strength or intensity of a sound. It is influenced by the amplitude of the sound waves.

2. **Amplitude and Loudness Relationship**: The loudness of a sound is directly proportional to the square of its amplitude. This means that if the amplitude increases, the loudness also increases significantly.

3. **Effect of Frequency**: While frequency affects the pitch of the sound, it does not directly influence loudness. Increasing frequency can change how we perceive the sound, but it does not inherently make it louder.

4. **Conclusion**: To increase the loudness of sound, we need to increase the amplitude of the sound waves. Therefore, the correct answer is to increase the amplitude.

### Final Answer:
To increase the loudness of sound, **increase the amplitude of the sound.**

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