Industrial noise control examples: Which statement(s) correctly describe practical methods to reduce noise from mills, chutes, and conveyor systems in plants?

Introduction / Context:
Noise abatement in process plants improves worker safety and regulatory compliance. Engineering controls—treating the source, path, and receiver—are preferred over relying solely on personal protective equipment.

Given Data / Assumptions:

• Equipment includes mills, vibrating chutes, and belt conveyors.
• Goal is general broadband noise reduction, not tonal-only issues.
• Physical retrofits are feasible.

Concept / Approach:
Effective noise control uses damping, isolation, absorption, and enclosure. For mills, acoustic enclosures lined with absorptive materials reduce radiated noise. For chutes, resilient liners (rubber) reduce impact and structure-borne vibration. For conveyors, compliant belt surfaces and coated rollers reduce rattling and idler noise.

Step-by-Step Solution:
Ball mills: apply source enclosure + internal absorption (fiberglass, mineral wool) to limit escape of noise energy.Vibrating chutes: add rubber liners to increase damping, cutting impact noise from falling or sliding material.Conveyors: select urethane-coated belts and rubber/plastic-covered rollers to reduce metal-on-metal noise and vibration.All three measures are standard practice → choose “All (a), (b) and (c)”.

Verification / Alternative check:
Industrial hygiene guides cite enclosures and damping as first-line engineering controls; noise surveys before/after retrofits typically show several dB(A) reductions.

Why Other Options Are Wrong:
Single-item choices omit other effective, common-sense controls.“None of the above” contradicts widely adopted practices.

Common Pitfalls:
Focusing on PPE alone; ignoring structure-borne vibration paths; neglecting maintenance (loose guards and misaligned rollers can dominate noise).

Final Answer:
All (a), (b) and (c)