Noise Control in IC engines Guided By, Rajesh Menon.B, Lecturer, Dept. of Mech Engineering. Presented By, Vineeth. S, S7MB, Roll No: 138.

INTRODUCTION Sound is the perception of vibrations stimulating the ear Sound is a periodic disturbance in fluids density, or in the elastic strain of a solid, generated by a vibrating object. These waves (vibrations) propagate in two basic ways: longitudinal waves and transverse waves.

What is Noise? Noise is a shadowy public enemy whose growing menace has increased in the modern age of industrialization and technological advancements. Continuous exposure to noise causes irreversible hearing loss, so control of noise pollution plays an important role as far as human health is concerned.

Basics Decibel:- The commonly used parameter for noise is the sound level in decibels.Human ears are sensitive in the frequency range of 20 Hz to 20 KHz Sound Pressure Level:- The non linearity and the very wide pressure range perceived by the human year led to the use of logarithmic scale for measurement and the quantitative value is called sound pressure level. SPL=10 log 10 {(Prms/pref) 2 ] Weighted Curve:- To adjust the frequency response of measuring systems to be similar to that of human ear,several weighting curves were proposed.’A’ weighted curve was designed to approximate to human response at low sound pressure levels(<55 db).Similarly ‘B’ and ‘C’ weighted curves at a sound pressure level of 55 to 85db and above 85db respectively.

W.C.Diagram ‘A’ Weighting Curve ‘B’ Weighting Curve ‘C’ Weighting Curve

Types of sources of noise Sources of noise are numerous, but may be broadly classified into two classes. They are, Industrial Non- industrial

INDUSTRIAL The industrial may included noises from various industries operating in cities like transportation, air crafts, rockets, defense equipments, explosions etc. NON-INDUSTRIAL The Non-industrial may include noises from loud speakers, microphone, radios, automobiles, trains, noises from various industries etc.

This is your ear Noise damage occurs HERE

Analysis and connection of noise problems, both elementary and complex, can be simplified by following a set of guidelines or principles…………

The principles of noise control are: Identify sources of noise and their relative importance List and evaluate possible noise control procedures as they apply to source, part and receiver Identify relative contributions from direct and reflected sound

Distinguish between absorption and attenuation of noise Identify and evaluate significance of flanking paths Identify and evaluate significance of structure born noise

Noise control in machines by modification in design………. In most of today's existing mechanical machines, the control of noise is an inevitable point which must be discussed Certain measures can be taken for noise control by making necessary variations and modification in the design of a mechanical machine

Modifications made in design Reduce impact forces Reduce the speed and pressures Reduce frictional resistance Reduce noise leakage Provide mufflers/silencers

Reduce impact forces Reduce the weight, size and height of all the impacting mass Cushion the impact by inserting a layer of shock- absorbing material One of the impact heads must be made of non- metallic material Smooth out acceleration of moving parts by applying accelerating forces gradually

Reduce the speed and pressures Fans, impellers, rotors, turbines and other moving or rotating components in a machine should be at the lowest speeds as much as possible In air ventilation systems, a 50 % reduction in the speed of air flow may lower the noise output by dB

Reduce frictional resistance All rotating parts of the machine must be well aligned Highly polished and smooth surfaces between sliding parts will reduce the noise Static and dynamic balancing of rotating parts reduces frictional resistance

Reduce noise leakage All unnecessary holes or cracks should be avoided. All the electrical or plumbing penetrations should be sealed with rubber gaskets. All the other openings should be covered with lids or rubber gaskets. Openings should be directed away from the operator and other people

Provide mufflers/silencers There is no distinction between mufflers and silencers. They can be classified into two.  Absorptive mufflers  Reactive mufflers Absorptive muffler absorbs the sound Reactive mufflers expand the sound waves with resultant self destruction

INTERNAL COMBUSTION ENGINE NOISE Several alternative methods can be used to classify internal combustion engine noise. The two most typical classification techniques are, oCLASSIFICATION BY NOISE CHARACTERISTICS oCLASSIFICATION BY ENGINE NOISE SOURCES

CLASSIFICATION BY NOISE CHARACTERISTICS AERODYNAMIC NOISE-aerodynamic noise includes exhaust gas and intake air noise as well as noise generated by cooling fans, auxiliary fans or any other air flow. COMBUSTION NOISE- combustion noise refers to noise generated by the vibrating surfaces of the engine structure, engine components and engine accessories after excitation by combustion forces. MECHANICAL NOISE-mechanical noise refers to noise generated by the vibrating surfaces of the engine components and engine accessories after excitation by reciprocating or rotating engine components.

CLASSIFICATION BY ENGINE NOISE SOURCES EXHAUST SYSTEM NOISE : This includes the noise from, Exhaust gas pulses leaves The vibrating surfaces of the exhaust system components. INTAKE SYSTEM NOISE: Intake system noise includes, Noise generated by the flow of air through the systems air inlet Noise emitted from the vibrating surface components. COOLING SYSTEM NOISE: Water cooled engines are typically cooled by using a radiator as a heat exchanger – with an axial flow fan is used to draw cooling air through the radiator. Air-cooled engines generally use a centrifugal fan in conjunction with shrouding to direct cooling air across the engine.

ENGINE SURFACE NOISE: Engine surface noise refers to sound emitted from vibrating surfaces of engine components and accessories and other than items included in the engine exhaust, in take and cooling systems. Engine surface noise is generally much higher for diesel engine than for gasoline engine Turbo charging of a diesel engine can result in some reduction of engine surface-radiated noise at high engine loads.

Noise evaluation during vehicles actual running Selection of acceleration (20m+Vehicle Length) 10m 7.5m B Point of Acceleration end A Point of Acceleration Commencement

Noise Control Legislation Most common form of state-enacted noise legislation applies to motor vehicles. Historically, trucks have been the first vehicles regulated, with regulations for automobiles, buses and motor cycles following. Motor vehicle regulations generally established a quantitative sound limit at a specified distance from the vehicle.

REMEDIES Stopping it at the Source Improving the engineering in many noisy objects has cut noise by nearly 30 decibels (i.e. snowmobiles). Government has set up regulations to manufacturers such as GM and Mack Truck to reduce vibration in heavy gears, axles, and transmissions. Reducing sound at the source by an average of 10 decibels cuts loudness in half.

Shielding your ears Without doubt, plugging up your ears is the cheapest and easiest method of noise control. If you have to be around loud noise, protecting yourself with ear plugs is better than doing nothing. Excessive exposure to loud noise and/or exposure to a quick loud noise could cause serious damage to your ears.

Conclusion Interest in noise and its reduction has become wide- spread in many industrially advanced countries. Noise standards and legislations exist in such countries for protecting urban residents and industrial workers from the hazard caused by excessive noise levels.In the mean while, as engineers, we should try to control noise to the extent possible by properly designing machines and appliances, by suitably locating machines and office spaces in industries and also by other advanced methods.

No Noise is Good Noise!

Thank You !!!!!!!