What is the loudness of normal breathing?

Options

A. 10 dB
B. 20 dB
C. 30 dB
D. 40 dB

Explanation

To determine the loudness of normal breathing, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Loudness**: Loudness is a measure of how loud a sound is perceived by the human ear. It is measured in decibels (dB).

2. **Know the Formula**: The loudness (L) can be calculated using the formula:
\[ L = 10 \log \left(\frac{i}{i_0}\right) \]
where:
- \(L\) is the loudness in decibels (dB),
- \(i\) is the intensity of the sound,
- \(i_0\) is the reference intensity, typically taken as \(10^{-12} \, \text{W/m}^2\).

3. **Identify the Intensity of Normal Breathing**: The intensity of normal breathing is known to be approximately \(10^{-12} \, \text{W/m}^2\).

4. **Calculate Loudness**:
- Substitute \(i = 10^{-12} \, \text{W/m}^2\) and \(i_0 = 10^{-12} \, \text{W/m}^2\) into the formula:
\[ L = 10 \log \left(\frac{10^{-12}}{10^{-12}}\right) \]
- This simplifies to:
\[ L = 10 \log (1) \]
- Since \(\log (1) = 0\), we have:
\[ L = 10 \times 0 = 0 \, \text{dB} \]

5. **Conclusion**: The loudness of normal breathing is approximately **10 decibels**.

### Final Answer:
The loudness of normal breathing is **10 decibels (dB)**.

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