Reflection noise is the correct answer.

Explanation:
When sound waves hit a surface, they can be reflected, transmitted, or absorbed. Reflection noise occurs when sound waves bounce off surfaces and create echoes or reverberations in a space. This can result in an increase in overall noise levels and decrease speech intelligibility. Reflection noise can be particularly problematic in spaces with hard, smooth surfaces such as walls and ceilings.

How sound absorbing materials work:
Sound absorbing materials are designed to reduce reflection noise by absorbing sound waves rather than allowing them to bounce off surfaces. These materials are typically soft, porous, and lightweight, and they have the ability to convert sound energy into heat energy. When sound waves pass through these materials, they cause the fibers or particles in the material to vibrate, which in turn converts the sound energy into heat. This reduces the amount of sound that is reflected back into the space.

Benefits of lining walls and ceiling with sound absorbing materials:
By providing lining on walls and ceiling with sound absorbing materials, the following benefits can be achieved:

1. Reduced reflection noise: The primary benefit of using sound absorbing materials is the reduction of reflection noise. These materials help to absorb sound waves, preventing them from bouncing off surfaces and creating echoes or reverberations in the space. This can result in a quieter and more acoustically comfortable environment.

2. Improved speech intelligibility: Reflection noise can make it difficult to understand speech, especially in larger spaces such as conference rooms or auditoriums. By reducing reflection noise, sound absorbing materials can improve speech intelligibility and enhance communication.

3. Enhanced sound quality: Reflection noise can distort or muffle sound, affecting the overall quality of audio playback. By minimizing reflection noise, sound absorbing materials can improve the clarity and fidelity of sound reproduction.

4. Increased privacy: Reflection noise can also result in a lack of privacy, as sound can easily travel through walls and ceilings. By reducing reflection noise, sound absorbing materials can help create more private and confidential spaces.

5. Aesthetic appeal: In addition to their functional benefits, sound absorbing materials can also be visually appealing. They are available in a variety of colors, textures, and designs, allowing them to be integrated seamlessly into the overall design of a space.

Conclusion:
By providing lining on walls and ceiling with sound absorbing materials, reflection noise can be effectively abated. These materials absorb sound waves, reducing the amount of noise that is reflected back into the space. This can result in a quieter and more acoustically comfortable environment, with improved speech intelligibility, enhanced sound quality, increased privacy, and aesthetic appeal.