Design for Low Noise. D. W. Herrin, Ph.D., P.E. University of Kentucky Department of Mechanical Engineering

Transcription

1 D. W. Herrin, Ph.D., P.E. Department of Mechanical Engineering

2 ISO Technical Report ISO TR 11688, Acoustics Recommended Practice for the Design of Low-Noise Machinery and Equipment, Part 1: Planning, Part 2: Introduction into Physics of Low Noise Design, ISO, Geneva, 1995 and M. Bockhoff, Design of Low-Noise Machinery, Chapter 66, Handbook of Noise and Vibration Control, ed. M. J. Crocker, Wiley, Hoboken, New Jersey (2007). 2

3 Establish Causal Chain for NVH Source Energy Path Receiver 3

4 ISO/TR and Bockhoff, 2007 A Candidate Design Process Clarification of Task Conceptual Design Detailed Design Prototyping 4

5 ISO/TR and Bockhoff, Clarification of Task Design Process Acoustic Control 1. Clarification of Task ü Clarifying standards, requirements, state-of-the-art ü List of specifications 1. Clarification of requirements concerning noise behavior ü Legal limits, standards ü Requests from clients ü State-of-the-art, sales argument For example ü A-Weighted sound power level ü A-Weighted emission sound pressure level ü Sound pressure spectra in one-thirdoctave bands ü Directivity index ü Psychoacoustic parameters such as loudness, roughness, and sharpness 5

6 ISO/TR and Bockhoff, Clarification of Task Example acoustic specifications list D/R Acoustic Specifications for Product Requirements R Maximum sound power of 85 db measured (ISO 3744) D Maximum sound power of 80 db measured (ISO 3744) R R Minimize structure-borne noise to the bed-plate Minimize structure-borne noise transmission between pump and motor D Desired R Required Setting targets early enables you to set noise levels for components from suppliers and set targets for yourself. 6

7 ISO/TR and Bockhoff, Conceptual Design Design Process 2. Conceptual Design ü Search for solution principles ü Comparison of different concepts ü Selection of concept Acoustic Control 2. Acoustical experience and knowledge for rough comparison of different solutions: ü Experience and examples ü Literature, drawings ü Source - Path Receiver maps ü Acoustical rules ü Formulas ü SEA / Ivanov Models Is numerical simulation helpful when you need it most? 7

8 ISO/TR and Bockhoff, Detailed Design Design Process 3. Detailed Design ü Choice of layout, components, materials, dimensions ü Comparison (modeling, computation) ü Selection of details Acoustic Control 3. Acoustical experience and knowledge for quantitative evaluation of different solutions: ü Source strength of partial sources ü Acoustical modeling, ranking ü Numerical Simulation (FEM, SEA) Steps to be taken ü Acoustical modeling ü Identify active and passive components ü Rank transmission paths ü Rules of noise control Are you allotted enough time for simulation? 8

9 Bockhoff, 2007 Design Process 4. Prototyping ü Functional checks ü Modifications ü Comparison with reference 4. Prototyping Acoustic Control 4. Evaluation and improvement of noise behavior: ü Noise measurements ü Modifications for noise reduction ü Final testing and comparison with reference Steps to be taken ü Measurements a. Overall check b. Detailed measurements (research sources and paths) ü Evaluation a. Ranking of sources b. Planning of noise control measures ü Modification a. According to priority list 9

10 Goetchius, Prototyping Advice for solving noise problems: 1. Stop, quiet your mind, and think about the problem. 2. Develop a hypothesis. 3. Test the hypothesis quickly if possible (smartphone apps, impact test) 4. Refine your hypothesis and develop a rigorous test. 5. Repeat steps 1 through 4 before bringing in the channel count champions (TPA, beamforming, etc.). 6. Keep your hypothesis in mind as your parse through the data. Never stop thinking, and never rely on analysis software to develop a solution. That s your job! 10