PASSAGE-III : The human voice can produce sounds with a frequency between 60 Hz and 1300 Hz. It is interesting to note that a normal human ear can hear sound of frequency between 20 Hz to 20,000 Hz. The sound of frequency greater than 20000 Hz is called ultrasonic and the sound of frequency below 20 Hz is known as infrasonic.
Frequency of ultrasonic sound is

Options

A. below 20 Hz
B. above 20 Hz
C. below 20000 Hz
D. above 20000 Hz

Explanation

To determine the frequency of ultrasonic sound, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Definitions**:
- The human voice can produce sounds with a frequency between 60 Hz and 1300 Hz.
- A normal human ear can hear sounds with frequencies ranging from 20 Hz to 20,000 Hz.
- Sounds with frequencies greater than 20,000 Hz are classified as ultrasonic.
- Sounds with frequencies below 20 Hz are classified as infrasonic.

2. **Identify the Frequency Range for Ultrasonic Sound**:
- According to the information provided, ultrasonic sound is defined as sound that has a frequency greater than 20,000 Hz.

3. **Select the Correct Option**:
- Given the options:
- Option 1: Below 20 Hz
- Option 2: Above 20 Hz
- Option 3: Below 20,000 Hz
- Option 4: Above 20,000 Hz
- Since ultrasonic sound is defined as having a frequency greater than 20,000 Hz, the correct option is Option 4: Above 20,000 Hz.

4. **Conclusion**:
- Therefore, the frequency of ultrasonic sound is above 20,000 Hz.

### Final Answer:
The frequency of ultrasonic sound is **above 20,000 Hz** (Option 4).

---