Fundamentals of sound:
Definition of NVH, Vehicle noise - Direct sound generation mechanism: airborne sound; Indirect sound generation mechanism: structure borne sound; Subjective response sound, Acoustic variables, basic attributes of sound such as wavelength, period, frequency; speed of sound, Decibel scale, Wave equation, types of sound fields, Measures of sound: Sound pressure, sound intensity and sound power, Combining sources: dB arithmetic, Standing wave, Beating, Impedance, Human hearing: frequency Versus sound pressure level, Loudness: phons and sones as noise descriptors; Weighting networks, Leqand various noise metrics for road noises.
Noise measurements and Instrumentation:
Measuring microphones, Sound level meter, time and frequency weighting, Sound spectra – Octave band analysis, Order analysis and waterfall plot, Various types of acoustic testing chambers, Sound power measurement from Sound pressure: Two- microphone probe for measuring; Sound power measurement from Sound Intensity
Sound fields and Room Acoustics:
Characterizing sound sources; Directivity; Sound Fields; Various approaches to modelling sound sources; Transmission loss (TL) and Insertion loss (IL); Reverberation time and Acoustic Absorption Coefficient; Effects of leaks on barrier and TL of composite barriers; measurement Absorption Coefficient and Transmission loss (TL).
Vehicle Interior and Exterior noise:
Internal noise sources in vehicles such as engine noise; road noise; aerodynamic (wind) noise; brake noise; squeak, rattle and tizz noises; sound package solution to reduce the interior noise: acoustic isolation, acoustic absorption and damping material solutions; Exterior noise sources in vehicles. such as air intake systems and exhaust systems; Tyre noise.
Sources of Vehicle Vibration:
Power train and Engine vibrations; driveline vibrations; chassis and suspension vibrations; Control strategies; Human response to vehicle vibrations, concept of harshness; subjective and objective evaluation of vehicle harshness.
Vibration Isolation and Control:
Introduction; damping of vibrations; vibration isolation and absorption; design of a Vibration Absorbers, unconstrained and constrained layer damping treatment, add on dampers and stiffeners, Introduction to Active Vibration Control.
Vibration Measurement and Instrumentation:
Definition of Modal Properties, Modal analysis theory, FE & Experimental modal analysis, Transducers and accelerometers Excitation sources Impact Excitation, Shaker excitation, Excitation signals, applications of Modal Analysis, laser based vibration measurements; analysis and presentation of vibration data.
Course outcomes:
At the end of the course the student will be able to:
CO1: understand and explain basics of Noise Vibration and Harshness.
CO 2: use different instruments and analyse the data for identification of sources of noise and vibrations.
CO3: understand /analyse, model and measure various sound and noise sources.
CO 4: identify the sources of vibration analyse the problem and suggest remedies for vibration damping.
CO5: posses the knowledge of vibration measurement and instrumentation.
Question paper pattern:
The SEE question paper will be set for 100 marks and the marks scored will be proportionately reduced to 60.
Textbook/ Textbooks
(1) Bies D. A. and Hansen C. H., Engineering Noise Control: Theory and Practice-, Spon Press, Taylor &Francis, NYUSA, 2003.
(2) Mathew Harrison, Vehicle Refinement- Controlling Noise & Road, Elsevier Publication, IstEdition, 2004
Reference Books
(1) William W. Seto, Theory and Problems of Mechanical Vibrations, McGraw Hill International BookCo., Singapore, Illustrated Edition, 1964
(2) S. S. Rao, Mechanical Vibrations, Pearson Education Inc., 5th Edition, 2010
(3) S. Graham Kelly, Mechanical Vibrations, Schaum’s Outline Series, Tata McGraw Hill Publishing Co.Ltd. SI Edition, 2000