*Question E4E02:
Which of the following types of noise can often be reduced by a digital noise reduction?*  

*Correct Answer is  D: All these choices are correct*  

### AI Response: (may contain errors)  

Digital noise reduction techniques are designed to identify and reduce unwanted noise in a signal. Let's look at each type of noise mentioned in the question:

1. **Broadband White Noise**:  
   - This type of noise is random and covers a wide range of frequencies. Digital noise reduction can effectively reduce this noise by identifying its random nature and filtering it out.

2. **Ignition Noise**:  
   - Ignition noise is typically impulsive and repetitive, often caused by the ignition systems in vehicles. Digital noise reduction can recognize the repetitive pattern and reduce its impact on the received signal.

3. **Power Line Noise**:  
   - This noise is usually caused by electrical equipment and can manifest as a hum or buzz. Digital noise reduction can help by identifying the specific frequency components of the noise and attenuating them.

**Correct Answer: D: All these choices are correct**  
- Digital noise reduction is versatile and can be applied to various types of noise, including broadband white noise, ignition noise, and power line noise. Therefore, all the choices are correct.

**Why the other choices are incorrect individually**:  
- Each choice (A, B, C) represents a type of noise that can be reduced by digital noise reduction. However, the question asks which types can be reduced, and since all can be reduced, the correct answer is "All these choices are correct."

In summary, digital noise reduction is a powerful tool that can be applied to a wide range of noise types, making it effective for all the options listed in the question.