Acoustics and Noise Control - Exam Revision Sheet

1. 📌 Essentials

• **Sound Pressure Level (SPL):**mic measure of sound pressure relative to a reference.
• Reverberation Time (T₆₀): time for SPL to decay by 60 dB in a room.
• Frequency Weightings: A-weighting mimics human; C-weighting is flat.
• Sound Power (Lw): total acoustic energy emitted by a source.
• Noise Barriers: reduce sound via reflection, absorption, and diffraction.
• Vibration Acceleration: peak $a_{peak} = \omega^2 x_{max}$; RMS $a_{RMS} = a_{peak}/\sqrt{2}$.
• Hearing Loss Types: conductive, sensorineural, presbycusis.
• Sabine's Equation: $T = 0.16 V / A$, relates room volume, absorption, and reverberation.
• Sound Level Addition: levels add logarithmically for uncorrelated noise; linear for coherent sources.
• Measurement Techniques: reverberant chamber for $L_{w}$, free-field for SPL.

2. 🧩 Key Structures & Components