Which of the following frequencies of sound can't be heard by human beings?

Options

A. 40 Hz
B. 400 Hz
C. 4000 Hz
D. 40,000 Hz

Answer

To determine which of the given frequencies of sound cannot be heard by human beings, we need to understand the range of human hearing.

### Step-by-Step Solution:

1. **Identify the range of human hearing**:
- The normal human hearing range is from 20 Hz to 20,000 Hz (or 20 kHz).

2. **List the given frequencies**:
- The frequencies provided are:
- 40 Hz
- 400 Hz
- 4000 Hz
- 40,000 Hz

3. **Check each frequency against the hearing range**:
- **40 Hz**: This frequency is within the range (20 Hz to 20,000 Hz), so it can be heard by humans.
- **400 Hz**: This frequency is also within the range, so it can be heard by humans.
- **4000 Hz**: This frequency is well within the range, so it can be heard by humans.
- **40,000 Hz**: This frequency exceeds the upper limit of human hearing (20,000 Hz), so it cannot be heard by humans.

4. **Conclusion**:
- The frequency that cannot be heard by human beings is **40,000 Hz**.

### Final Answer:
- **40,000 Hz** is the frequency that cannot be heard by human beings.

---