Introduction

Noise-Control Strategies (Sound source modification, control of transmission path, modification of receiver path, Airborne and structure-borne noise)

Acoustic Field Variables: pressure and velocity fields, sound speed, acoustic potential

Wave equation and its solution: Plane and spherical waves, Progressive and Standing waves

Concepts of time and frequency-domain representations

Open and closed-end boundary conditions, resonances in 1-D ducts,

Acoustic Impedance, Near- and Far-field, Intensity and Sound Power

Units: Sound Pressure, Intensity and Power levels

Combining Sound Pressures: Adding of coherent and incoherent sound pressures, Beating phenomenon, Subtracting sound pressure levels

Analytical solution of plane wave propagation in 1-D ducts

Radiation impedance at a pipe end with and without flange

Lumped System Analysis: Inertance and Compliance

Lumped Analysis of a uniform pipe closed/open at an end, concept of end-correction

Helmholtz Resonator, Quarter-wave resonators, Extended-tube resonators, Concentric Hole-Cavity Resonators,

Electro-Acoustic Analogy and Layout of a typical engine exhaust system, Thevenin and Norton forms

Classification of muffling devices: Reactive dissipative, and hybrid mufflers,

Muffler Performance Measures: Insertion Loss, Transmission Loss & Level Difference

Simple Area Discontinuity & Transfer Matrices (Four-pole parameters)

Impedance matrix characterization

Expression for Transmission Loss performance

Simple Expansion chamber analysis using Transfer Matrix method

Extended-Inlet and Extended-Outlet Muffler Analysis

Side-Inlet and Side-Outlet Muffler using Transfer Matrix method

Extended-Inlet and Side-Outlet Analysis using Transfer Matrix method

Wave propagation in gradually varying area ducts: Webster’s horn equation

Exponential and Conical ducts, Segmentation and Matrizant approaches

Aeroacoustic state variables Transfer Matrix for a Tubular Element (Uniform pipe)

Transfer matrix for Extended-Inlet and Outlet element & Use of perforated elements in commerical mufflers

Two-interacting duct configurations: Concentric Tube Resonators (Fully and partially perforated)

Review of Perforate impedance expressions

Cross-Flow elements of expansion- and contraction-type, Plug-mufflers and Three-pass perforated tube mufflers

Multiply-connected mufflers: Herschel-Quincke (HQ) Tubes

Network analysis and Integrated transfer matrix method for complex muffler configurations, Conical Concentric Tube Resonators (CCTRs)

3-D Acoustic Wave Equation in Rectangular and Circular Waveguides: Derivation, Modal Solution and Concept of Cut-on Frequency

Three-dimensional muffler analysis: Necessity, Overview of different analytical methods

Green's function or Point-Source Model, Piston-driven model - Expansion and Flow-Reversal chambers, Side-inlet and side-outlet systems

Analytical mode-matching method for extended-inlet and extended-outlet muffler element

Dissipative mufflers: Local and bulk reaction type, lined duct silencers, flow effects, hybrid or combination type silencers, parallel baffle silencers, Pod silencers

Pressure-Drop considerations

Requirements & Practical considerations of an Engine Exhaust Muffler including guidelines on design of muffler shell and end-plates

Topics for future courses: Experimental method in muffler acoustics and engine source characteristics, Numerical techniques such as Finite-Element Analysis, Break-out noise considerations

Assignment problems