Phon is a unit of

Options

A. Wavelength
B. Loudness
C. Frequency
D. Intensity

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks about the unit "phon." We need to identify what this unit measures.

2. **Identifying the Context**: The term "phon" is related to sound and its perception. It is essential to know that it is not a unit of physical measurement like meters or kilograms.

3. **Defining Phon**: The phon is a unit of loudness. It measures how loud a sound is perceived by the human ear. This measurement is based on the frequency of the sound and how humans perceive different frequencies at varying loudness levels.

4. **Conclusion**: Therefore, the answer to the question is that the phon is a unit of loudness.

**Final Answer**: Phon is a unit of loudness.

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