CHAPTER 1 INTRODUCTION SOUND AND NOISE.pptx

This notes discuss about the principle of sound and noise

1. SOUND AND NOISE

2. Introduction Sound is a form of energy produced by vibrations that travel through a medium (solid, liquid, or gas). Noise is unwanted or unpleasant sound that can cause disturbance, stress, or health problems.

3. Basic Concepts of Sound Sound travels as longitudinal waves. Key characteristics: Frequency (Hz): number of vibrations per second Wavelength (m): distance between wave peaks Amplitude: maximum displacement Velocity (m/s): speed of sound through medium Formula: v = f × λ

4. Speed of Sound in Different Media Air (20°C): 343 m/s Water: 1480 m/s Steel: 5960 m/s Note: Sound travels fastest in solids and slowest in gases.

5. Sound Intensity and Loudness Intensity: sound energy per unit area (W/m²) Loudness: subjective perception of intensity Measured in decibels (dB) Formula: L = 10 log₁₀(I/I₀), where I₀ = 10⁻¹² W/m² Typical levels: Whisper: 30 dB Conversation: 60 Db Traffic: 80 dB Rock concert: 110 dB

6. Noise Definition: Unwanted or disturbing sound affecting comfort, communication, or health. Types of Noise: 1. Continuous (e.g., machinery hum) 2. Intermittent (e.g., traffic) 3. Impulse (e.g., explosion, gunfire)

7. Sources and Effects of Noise Sources: Industrial – machines, compressors Transportation – vehicles, aircraft Community – construction, loud music Effects: Hearing loss, tinnitus Stress, fatigue, sleep disturbance Communication interference

8. NOISE MEASUREMENT 1. Sound Level Meter (SLM) 2. Noise Dosimeter 3. Octave Band Analyzer

9. Noise Measurement Weightings: A-weighting (dBA): reflects human ear sensitivity C-weighting ( dBC ): used for high-level sounds

10. Control and Management of Noise Noise Control Hierarchy: 1. At the Source – quieter machines, maintenance 2. Along the Path – barriers, enclosures 3. At the Receiver – earplugs, earmuffs, job rotation Exposure limit: 85 dBA for 8 hours (WHO/OSHA)

11. Summary Sound is vibration energy traveling through a medium. Noise is unwanted sound causing disturbance or harm. Proper measurement and control protect health and comfort.

12. References • World Health Organization (WHO), Guidelines for Community Noise (1999) • OSHA, Occupational Noise Standard (29 CFR 1910.95) • DOSH Malaysia, Guidelines for Noise Exposure and Control