In building acoustics, which of the following materials is most suitable to use inside partition walls as a sound absorbing material?

Introduction / Context:
Noise control and room acoustics are important in homes, offices, cinemas and studios. One common method of reducing sound transmission between rooms is to use sound absorbing materials inside partition walls. This question checks whether you can identify which of the given materials is actually effective at absorbing sound energy rather than reflecting it, a key idea from basic acoustics and building physics.

Given Data / Assumptions:

• We are dealing with partition walls between rooms.
• The goal is to absorb sound, not just reflect or transmit it.
• The materials offered are stone chips, steel, glass wool and glass pieces.
• Only one of these materials has the highly porous, fibrous structure ideal for sound absorption.

Concept / Approach:
Good sound absorbing materials are usually porous, fibrous and lightweight. When sound waves enter such materials, air inside the pores oscillates and friction converts sound energy into heat, reducing reflections and transmission. Glass wool is a fibrous insulating material made from very fine glass fibres and has excellent sound absorption and thermal insulation properties. In contrast, dense and hard materials such as stone, steel or solid glass mostly reflect sound rather than absorb it. Therefore, glass wool is widely used in false ceilings, wall cavities and acoustic panels to absorb sound.

Step-by-Step Solution:
Step 1: Recall that sound absorbing materials should be soft, porous and fibrous.Step 2: Examine each option and classify it as hard/dense or porous/fibrous.Step 3: Stone chips are heavy and rigid, so they reflect sound instead of absorbing it.Step 4: Steel is a hard metal with high reflectivity for sound and is a poor absorber.Step 5: Glass pieces are brittle and rigid, again reflecting most of the sound energy.Step 6: Glass wool consists of fine glass fibres forming a porous mat, which allows sound to enter and be dissipated.Step 7: Conclude that glass wool is the best sound absorbing material among the given options.

Verification / Alternative check:
In practical construction and acoustic treatment, glass wool or mineral wool is routinely specified inside partition walls and acoustic panels. Soundproofing tutorials and engineering handbooks repeatedly recommend fibrous materials like glass wool, rock wool or foam for internal absorption. You rarely see solid stone, plain steel sheets or loose glass pieces recommended as absorbers; they are instead structural or decorative elements. This real world practice confirms that glass wool is the most appropriate choice.

Why Other Options Are Wrong:
Stone chips are dense and mainly used for structural concrete, not for absorbing sound; they reflect sound strongly. Steel has a very hard and smooth surface and typically reflects sound, which can even cause echoes in metal-walled spaces. Glass pieces have similar reflective properties and are not designed as acoustic absorbers. All three therefore fail the basic requirement of high porosity and internal friction needed for effective sound absorption.

Common Pitfalls:
Sometimes, students think that heavier materials always block sound better and mistakenly choose stone chips or steel. While heavy materials can reduce transmission, this question specifically asks for sound absorbing material inside partition walls, which refers to internal absorption, not just mass. Remember that for absorption you want soft, porous and fibrous materials, with glass wool being a classic example used in many buildings.

Final Answer:
Glass wool is the best material among the options for sound absorption in partition walls.