Design Acoustics: Primary and Secondary Noise Mitigation

Description

This technical book focuses on the acoustic analysis of weak points in a comprehensible manner. This reliably helps the designer and acoustician to understand the noise development of machines and systems and to develop suitable primary and secondary noise reduction measures.  Selected application examples from practice support the user in developing his own ideas for the implementation of product-related noise reductions. Preface Preface to the English Edition List of Formula Sizes Contents 1: Introduction and Motivation 2: Physical Basics 2.1 Terms 2.2 Sound Field Quantities, Wave Equation 2.2.1 Acoustic Impedance 2.2.2 Sound Intensity 2.2.3 Sound Power 2.2.4 Mechanical Impedance 2.2.4.1 Mechanical Impedances of Idealised Components 2.2.4.2 Mechanical Input Impedance of Real Components 2.2.5 Structure-Borne Sound Power 2.2.6 Degree of Radiation 2.3 Sound Level 2.3.1 Level Addition, Energetic Addition 2.3.2 Averaging Level 2.3.3 Noise Level 2.3.4 A-weighted Level 2.3.5 Rating Level 2.3.5.1 Neighbourhood Noise 2.3.5.2 Work Noise 2.4 Temporal and Spectral Representation of Sound Field Quantities 2.4.1 Periodic Time Course 2.4.2 Random, Stochastic Time History, General Noise 2.5 Level Reduction by Sound Reflection and Sound Absorption 2.5.1 Sound Insulation 2.5.2 Sound Attenuation 2.5.3 Equivalent Absorption Area A 2.5.3.1 Reverberation Time T 2.5.3.2 Reverberation Radius rH 2.6 A-sound Power Level LWA References 3: Sound Generation 3.1 Sound Generation Through Flow Processes 3.1.1 Sound Generation Due to Velocity Fluctuations 3.1.2 Sound Generation Due to Fluctuations in Flow Rate and Alternating Forces 3.1.2.1 Noise Generation Due to Fluctuations in the Flow Rate 3.1.2.2 Sound Generation Through Impulse-like Pressure Equalisation Processes 3.1.3 Aeropulsive Noise 3.1.4 Noise Generation Due to Vortex Formation 3.1.5 Noise Generation by Free Jets 3.1.6 Noise Generation-due to Intake Noise 3.1.7 Noise Generation in Turbulent Boundary Layers 3.1.7.1 Sound Radiation from Pipelines 3.1.8 Example: Noise Generation of a straight Pipeline 3.1.8.1 Total Internal Sound Power Level of a Centrifugal Fan 3.1.8.2 Total Internal Sound Power Level due to Pipe Flow 3.2 Sound Generation by Mechanical Vibrations, Structure-Borne Sound 3.2.1 Excitation of Structure-Borne Sound, Excitation or Alternating Force 3.2.1.1 Periodic Excitation 3.2.1.2 Impulse or Shock Excitation 3.2.1.3 Stochastic Excitation References 4: Measuring Technology 4.1 National and International Standardisation 4.1.1 Emission Sound Pressure Level at the Workplace 4.1.2 Sound Power Level by Measuring the Sound Pressure Level 4.1.2.1 Basic Standards 4.1.2.2 Enveloping Surface Method 4.1.2.3 Reverberation Chamber Method 4.1.3 Sound Power Level by Measuring the Sound Intensity Level 4.1.4 Sound Power Level by Measurement of the Structure-Borne Sound Level 4.2 Sound and Vibration Measurement Techniques 4.2.1 Sound Pressure Measurement 4.2.2 Sound Intensity Measurement 4.2.3 Structure-Borne Sound Measurement 4.3 Direct Determination of the A-total Sound Power Level 4.3.1 By Sound Pressure Measurement 4.3.2 By Sound Intensity Measurements 4.4 Indirect Determination of the A-total Sound Power Level 4.4.1 Partial Airborne Sound Power Level 4.4.2 Partial Structure-borne Sound Power Level by Sound Intensity Measurements 4.4.3 Partial Structure-Borne Sound Power Level by Structure-Borne Sound Measurements References 5: Noise Reduction 5.1 Primary Noise Reduction 5.1.1 Acoustic Weak Point Analysis 5.1.1.1 Separation of Airborne and Structure-Borne Sound 5.1.1.2 Data Acquisition for the Energy Balance Sheet 5.1.2 Basic Measures for Noise Reduction 5.1.2.1 Influencing the Generation of Sound 5.1.2.2 Influence of Insulation on Structure-Borne Sound Transmission 5.1.2.3 Influence of Damping on Structure-Borne Sound Transmission 5.1.2.4 Influence of Elastic Decoupling on Structure-Borne Sound Transmission 5.1.2.5 Influencing the Radiation of Structure-Borne Sound 5.1.3 Principles of Design Acoustics 5.2 Secondary Measures 5.2.1 Enclosure, Acoustic Enclosure 5.2.1.1 Basic Construction of an Acoustic Enclosure 5.2.1.2 Openings, Leaks 5.2.1.3 Structure-Borne Sound 5.2.2 Silencer 5.2.2.1 Absorption Silencer Components and Characteristics of a Splitter Attenuator Estimating the Attenuation of an Absorption Silencer 5.2.2.2 Resonance Silencer Plate Resonators Helmholtz Resonator The λ4 Resonator 5.2.2.3 Reflective Silencers References 6: Practical Examples 6.1 Drive Unit 6.1.1 Noise Reduction Planning 6.1.2 Acoustic Weak Point Analysis of the Drive Foundation 6.1.3 Noise Reduction Measures 6.2 Packaging Machine 6.2.1 Design Acoustic Weak Point Analysis 6.2.2 Noise Reduction Plans 6.2.3 Noise Reduction Measures in Principle 6.3 Straddle Carrier (Mobile Crane) 6.3.1 AcousticWeak Point Analysis 6.3.2 Noise Reduction Plans 6.3.3 Noise Reduction Measures 6.4 Shell and Tube Heat Exchanger 6.4.1 Sound and Vibration Weak Point Analysis 6.4.2 Model Tests 6.4.3 Constructional Noise Reduction Measures 6.5 Acoustic Optimisation of a Vane Gearbox 6.5.1 Weak Point Analysis 6.5.2 Noise Reduction Measures 6.6 Vibration Reduction 6.6.1 Cause of Vibration-Induced Damage to the Slideway Supports of a Tablet Press 6.6.2 Vibration Reduction in Pipelines 6.7 Field-Tested Application Examples 6.7.1 Sound Generation 6.7.2 Sound and Vibration Transmission 6.7.3 Sound Radiation 6.7.4 Interaction of Different Mechanisms of Action References Index