FORM - 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)
Title:
INTEGRATED DISSIPATIVE AND REACTIVE MUFFLER WITH TUNED FLUTE-LIKE PERFORATED TUBES
Applicant:
MAHINDRA & MAHINDRA LIMITED
GATEWAY BUILDING, APOLLO BUNDER,
MUMBAI-400001,
MAHARASHTRA, INDIA.
Inventors:
R. P. SENTHIL KUMAR, M. SAKTHI BABU, VENKATESWARARAO MANCHI, G. NAGARAJAN, TANMAY S. DESHPANDE
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE USED.

FIELD OF INVENTION
The present invention relates to device for suppressing sound, particularly an integrated dissipative and reactive muffler with flute-like perforated tubes and sound absorbing materials for suppression of noise and thereby improving the quality of sound emanating from the muffler.
BACKGROUND OF THE INVENTION
One of the most important senses of the living being including human is the sense of hearing. Generally, SOUND is what human ears hear, whereas the NOISE is undesirable sound. Technically speaking, sound is produced when a variation in air pressure exists in the region adjacent to the ear. When the variations in air pressures near the ears reach extremely high amplitude, the sound becomes unbearable or annoying to human ears. The human ear can bear a wide range of sounds, so it was felt necessary to devise a decibel (dB) scale for expressing the sound levels. On this decibel scale, human hearing can be measured from a range of zero (0 dB) to a range of 140 dB, beyond which the human beings experience pain, so this is the human threshold of pain. There are different types of dB scales, i.e. A, B, C, D and L. The "A" weighting network weights a signal in a manner which approximates to an inverted equal loudness contour at low Sound Pressure Levels, the "B" network corresponds to a contour at medium Sound Pressure Levels and the "C" network to an equal loudness contour at high Sound Pressure Levels. A specialized characteristic, the "D" weighting, has also been standardized for aircraft noise measurements. However, the human ear does not experience all sound frequencies as equally loud.
Since the human ear is most sensitive to the frequencies in the range of 1000 to 4000 Hz, it correlates well with A- weighted scale dB (A). Hence this scale was devised to use an approximation of loudness, i.e. "A-weighting filter" for correcting the sound pressure level to accurately reflect the perception of human ears.
According to a White Paper entitled- "Generator set Noise Solutions" and written by Dennis Aaberg, Senior Acoustics Specialist of Cummins Power Generation, there are six main categories of noises produced in diesel generator-sets. These are as under:

(i) Engine noise, typically in the range of 100 dB(A) which is produced by
mechanical and combustion forces and typically ranges from 100 dB(A) to
121 dB(A) measured at 1m distance depending on the size of the engine, (ii) Engine exhaust gas noise, typically in the range of 120 dB(A) to 130 dB(A)
and higher without silencer, which can be reduced by a minimum of 15 dB(A)
with a silencer, (iii) Cooling fan noise, typically in the range of 100 dB(A) to 105 dB(A) at 1m
distance resulting from the sound of air being move at high speed across the
engine and through the radiator, (iv) Alternator noise, typically in the range of 80 dB(A) to 90 dB(A) at 1m
distance and caused by carbon brush friction, (v) Induction noise, typically in the range of 80 dB(A) to 90 dB(A) at 1m distance
and caused by fluctuations in current in the alternator windings, which give
rise to mechanical noise, (vi) Structural/mechanical noise caused by mechanical vibration of various
structural parts and components and which is radiated as sound,
However, two types of noises are particularly observed during the operation of diesel generator sets. First is the low frequency noise related combustion of diesel engine and the second noise is generated due to the flow of exhaust gases.
PRIOR ART
The conventional method for lowering the exhaust gas flow noise, sound absorbers are used either in the muffler or as separate parts, whereas for suppressing the low frequency combustion noise, the tubes, holes and volume of the muffler is utilized.
The earlier patent application number 282/MUM/2013 filed by the same applicant discloses a muffler with multiple fluted tubes for sound suppression in automobiles comprising a closed longitudinal main body having outer shell (7) with end plates at both side of geometrical cross-section. A first chamber (7A) and a second chamber (7B) are formed and separated in the said body by a baffle (4) having small series of holes through therein. An inlet pipe at one end of said body provided in the first chamber at central axis thereof for the exhaust gas to enter into said body. A first divergent pipe (2) is attached to said inlet pipe at said first chamber. At

least two numbers of fluted tubes, each having a through hole in the upstream of pipe (3) and series of holes in the downstream parallel to and at a distance from the longitudinal axis of said body is provided to pass through and is supported in said baffle. An outlet pipe (5) in said second chamber is provided at the other end at the central axis of said body. A second divergent Pipe (6) is attached to said outlet pipe projecting out of said body. However, this muffler is configured to suppress the sound generated at higher frequencies, particularly without using the sound absorptive materials, such as glass wool. This muffler also uses a pair of divergent tubes for reducing the back pressure. Moreover, in this configuration, the direction of exhaust gas flow is straight from the inlet to outlet in order to directly muffle the sound of exhaust gas flow in a pulsating automobile engine. Therefore, this muffler achieves a good Sound Transmission Loss (STL) in higher frequency range. Here, it shows a better performance (Fig. 3) at higher frequency ranges.
DISADVANTAGES WITH THE PRIOR ART
The following are the disadvantages with the muffler discussed above:
- Effective only for higher ranges of frequencies, i.e. 750-1500 Hz and 2000-2500 Hz,
- No sound absorbing material is used, so performance is relatively poorer,
- Particularly useful in automotive diesel engines, and
- Not suitable for diesel generator sets having larger capacities.
OBJECTS OF THE INVENTION
Some of the objects of the present invention - satisfied by at least one embodiment of the present invention - are as follows:
An object of the present invention is to provide a muffler with flute-like perforated tubes for improving sound quality of the generator running on diesel fuel.
Another object of the present invention is to provide a muffler for low frequency noise generated in a diesel generator set.
Still another object of the present invention is to provide a low-noise, large-capacity diesel generator set equipped with a muffler using sound absorbing material.

Yet another object of the present invention is to provide a muffler with flute-like perforated tubes that is cost-effective and efficient to operate.
A still further object of the present invention is to provide a muffler with flute-like perforated tubes, which reduces high frequency exhaust flow-noise in stages.
A yet further object of the present invention is to provide a muffler with flute-like perforated tubes, which also reduces low frequency diesel combustion noise.
These and other objects and advantages of the present invention will become more apparent from the following description, when read with the accompanying figures of drawing, which are however not intended to limit the scope of the present invention in any way.
SUMMARY OF THE INVENTION
In accordance with the present invention, there is provided an integrated dissipative and reactive muffler with tuned flute-like perforated tubes, the muffler comprising:
- at least one inlet pipe and at least one outlet pipe;
- at least one set of flute-like perforated tube disposed parallel to each other and in-line with the inlet and outlet pipes for suppressing the noise generated in a diesel generator set;
- a first end cover on the inlet side and a second end cover closing one end of the muffler;
- at least four of baffle plates disposed between the end covers configuring at least five hollow chambers therebetween and providing a circuitous path for allowing the exhaust gas flow through the muffler;
- the first baffle plate being disposed near the first end cover forming a first hollow chamber and the fourth baffle plate being disposed near the second end cover forming a fifth hollow chamber; and
- the first and the fifth chambers being packed with at least one sound absorbing material compacted in a predetermined density in the available hollow space in the respective chamber;

wherein, the length of the flute-like perforated tubes and the inlet and outlet pipes are respectively adapted to be tuned according to the firing frequency of the diesel generator set.
Typically, the series of holes provided on each set of the flute-like perforated tubes which are disposed facing each other and also running parallel to each other and at least a portion of the sets of tubes are spaced apart by means of a non-perforated and continuous partition to prevent flow of exhaust gas between through the partition.
Typically, the sound absorbing material of a predetermined density is packed within the available hollow space in a first chamber formed between the first end cover and the first perforated baffle plate disposed adjacent thereto.
Typically, the sound absorbing material of a predetermined density is completely packed within the fifth chamber formed between the second end cover and the completely perforated baffle plate disposed adjacent thereto.
Typically, the muffler is circular and comprises a corresponding first end cover with an aperture for introducing the inlet pipe and/or exiting the outlet pipe at one end and a second end cover to completely close the other end of the muffler, and the baffle plates also supporting the inlet pipe and outlet pipe in the corresponding apertures provided therein.
Typically, the muffler is configured elliptical, rectangular, oval, square-shaped or in any other profiled hollow structural shape.
Typically, the inlet pipe includes a plurality of holes on its surface exposed inside the muffler; the first set of tubes have a plurality of holes at one end thereof which is disposed near the inlet side end of the muffler and a single hole near the other end thereof, the first set of tubes completely disposed in-line with the inlet pipe; and the length of the first set of tubes and the length the inlet pipe are tuned according to the firing frequency of the respective diesel generator set.
Typically, the outlet pipe includes a plurality of holes at least on a portion of its surface exposed inside the muffler; the second set of tubes have a plurality of holes approximately at the center thereof which is disposed near the inlet side end of the

outlet pipe and a single hole near the other end thereof protruding out of the outlet pipe; the length of the second set of tubes and the length the outlet pipe are tuned according to the firing frequency of the respective diesel generator set.
Typically, the baffle plate supporting the inlet pipe end adjacent the second end cover includes perforations only on the upper half portion thereof.
Typically, the baffle plate disposed between the first baffle plate forming the inlet side chamber with the first end cover is packed with sound absorbing material and includes perforations throughout its surface for passage of exhaust gases.
Typically, the chamber formed between the baffle plate supporting the inlet pipe-end adjacent the second end cover includes perforations only on the upper half portion thereof.
Typically, the chamber configured between the second baffle plate and the third baffle plate is sub-divided into an upper half chamber and a lower half-chamber by means of a non-perforated continuous partition disposed horizontally therebetween, the third baffle plate having perforations only on the upper half thereof disposed above said partition; and the lower half chamber being further sub-divided into two smaller chambers by means of a half baffle plate having holes on surface thereof and also supporting the outlet pipe adjacent inlet end thereof.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The present invention will be briefly described with reference to the accompanying drawings, wherein:
Figure 1 shows a muffler configured with two sets of flute-like perforated tubes for suppressing the low frequency noise generated in a diesel generator set;
Figure 2 shows the perforations provided on the inlet pipe of the muffler of Figure 1;
Figure 3 shows the flute-like perforated tube of the first set provided in the inlet pipe thereof;
Figure 4 shows the perforations provided on the outlet pipe of the muffler of Fig. 1;

Figure 5 shows the flute-iike perforated tube of the second set of provided in the outlet pipe thereof;
Figure 6 shows the end covers and baffle plates and of muffler shown in Figure 1;
Figure 7 shows the inlet pipe in front and side views respectively;
Figure 8 shows the outlet pipe in top, front and side views respectively;
Figure 9 shows the exhaust gas flow through the muffler for an automobile according to an earlier patent application by the same applicant as for the present invention;
Figure 10 shows the exhaust gas flow through the muffler for a diesel generator set in accordance with the present invention as already shown in Fig. 1;
Figure 11 shows the sound transmission loss (STL) in decibels for the muffler according to an earlier patent application by the same applicant for an automobile as shown in Fig. 7;
Figure 12 shows the sound transmission loss (STL) in decibels for the muffler for a diesel generator set in accordance with the present invention as already shown in Figures 1 and 8;
Figure 13 shows a perspective detailed view of the second embodiment of the muffler for a diesel generator set in accordance with the present invention as shown; and
Figure 14 shows another detailed view of the third embodiment of the muffler for a diesel generator set in accordance with the present invention.
DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS
In the following, the muffler configured with flute-like perforated tubes in accordance with the present invention configured for a diesel generator set will be described in

more details with reference to the accompanying drawings without limiting the scope and ambit of the present invention in any way.
Figure 1 shows the first embodiment of the muffler 100 in accordance with the present invention. Preferably, the material of the muffler body is metallic, more preferably a cold roller close annealed coil (CRCA). The muffler 100 is configured with two sets of flute-like perforated tubes 16, 18 for suppressing the low frequency noise generated in a diesel generator set. The muffler 100 is made-up of a hollow body closed at one end by a first end cover 2 at one end having aperture for the inlet pipe 20. In this embodiment, the muffler 100 is divided into in a plurality of compartments by means of baffle plates 4, 6, 8, 10 and 12 respectively. The outlet pipe 30 protrudes out laterally from an opening directed downwards in the first compartment configured by the first end cover 2 and the baffle plate 4 (Figures 1 and 10). The empty space in this compartment is filled with a sound absorbing material 28, such as glass wool, however not restricted to this material. Preferably, the density of the filled Glass wool is in a range of 50 to 75 kg/m3. And the weight of the same is about 2 to 3 kg. The compartment configured between the baffle plate 12 and the second end cover 14 of the muffler 100 is also filled with a sound absorbing material 26, such as Glass wool. Preferably, the density of the filled Glass wool is in a range of 50 to 75 kg/m3. And the weight of the same is about 1 to 2kg. The inlet pipe 20 extends through baffle plates 4, 6 and 10. Similarly, outlet pipe 20 extends through the baffle plates 4, 6 and half baffle plate 8. The compartment configured between the baffle plates 6 and 10 is also sub-divided into two chambers by means of a continuous partition 24, which divides it in an upper chamber containing the inlet pipe 20 and a lower chamber containing the outlet pipe 30. Preferably the baffles plates are also made of CRCA. The first end cover 2 has an opening for the inlet pipe 20. In the first set, the flute-like perforated tubes 16 are disposed parallel to each other and in-line with the inlet pipe 20 for suppressing the noise generated in a diesel generator set. Preferably, the holes in each pair of the flute-like perforated tubes are facing each other. In the second set also, the flute-like perforated tubes 18 are disposed parallel to each other and in-line with the outlet pipe 30 for further suppressing the noise generated in a diesel generator set. Preferably, the holes in the perforated tubes of each set are facing each other. The length of the flute-like perforated tubes and the inlet tube 20 are tuned according to the firing frequency of the respective diesel generator set. Thus, these flute-like perforated tubes suppress

the low frequency noise levels and the sound absorbing materials 26 and 28 control the exhaust gas flow noise due to combustion.
Figure 2 shows the inlet pipe 20 of the muffler 100 shown in Figure 1. The inlet pipe 20 has a plurality of perforations on its circumferential surfaces all over its length.
Figure 3 shows the flute-like perforated tubes 16 disposed parallel to each other and in-line with the Inlet pipe 20 for suppressing the noise generated in a diesel generator set. The length of the flute-like perforated tubes 16 and inlet tube 20 are tuned according to the firing frequency of the respective diesel generator set for efficiently suppressing the low frequency noise.
Figure 4 shows the outlet pipe 30 of the muffler 100 shown in Figure 1. The outlet pipe 30 has a plurality of perforations on its circumferential surfaces only on a portion of its length lying beyond baffle plate 8 toward the close end of the muffler 100 and in the region 2 and 4 marked in Figure 1.
Figure 5 shows the flute-like perforated tubes 18 disposed parallel to each other and in-line with the outlet tube 20. These tubes 18 have a different length as compared to flute like tubes 16 and have a typical pattern of holes almost similar to tubes 16.
Figure 6 shows the first end cover 2 having only one aperture for inlet pipe 20. The baffle plates 4 and 6 have two apertures each corresponding to the inlet pipe 20 and outlet pipe 30 respectively. The half baffle plate 8 has only one aperture corresponding to the outlet pipe 30. The baffle plate 10 also has only one aperture corresponding to the inlet pipe 20 and the lower portion has no perforations. It has perforations only on the upper circumference thereof. This allows the exhaust gases to be redirected to the outlet pipe 30. The baffle plate 12 is perforated throughout its surface. The second end cover 14 has no holes and completely closes the other end of the muffler.
Figure 7 shows the inlet pipe 20 in front view A and side view B respectively. The inlet pipe 20 is also provided with a flange for allowing fastening to the exhaust gas pipe coming after combustion of diesel fuel in the generator.

Figure 8 shows the outlet pipe 30 in front A and side view B and top view C respectively. This outlet pipe 30 may also have a flange similar to inlet pipe 20 for connecting it to exhaust gas outlet.
Figure 9 shows the exhaust gas flow through the muffler 50 for an automobile according to an earlier patent application by the same applicant. In this muffler is divided into two compartments 7A and 7B. The exhaust gases 1 coming in through the divergent inlet pipe 20 hitting the baffle plate 4 is redirected to the flute-like perforated tubes 3 disposed parallel to each other and in-line with the inlet tube 2 and pass through the chamber 7B. Some of the inlet gases hitting the baffle plate 4 directly pass through the perforations therein to be led further towards the outlet pipe 6, which is also shaped divergent. The complete gas flow through this muffler 50 is shown in red colored arrows.
Figure 10 shows the exhaust gas flow through the muffler 100 in accordance with the present invention. The inlet pipe 20 guides the exhaust gases into the muffler chamber configured between the baffle plates 10 and 12, which are then directed towards the perforated baffle plate 12 disposed close to the second end cover 14 of the muffler 100. The baffle plate 12 is perforated throughout its surface to allow the exhaust gases exiting the inlet pipe 20 and hitting the completely perforated baffle plate 12 to interact with the sound absorbing material, such as Glass wool, packed between the baffle plate 12 and the closed end 14 of the muffler 100. This interaction facilitates to suppress the exhaust gas flow noise and thereby reduces the flow noise levels. This way, major portion of the exhaust gases are returned through the first set of flute-like perforated tubes 16 and then are passed through the sound absorbing material 28 through baffle plate 4. Since the first set of flute-like perforated tube diameter 16 is smaller than the inlet pipe 20, the impedance is increased. This result in a substantial reduction in the Low frequency diesel generator noise produced due to combustion of diesel fuel. Subsequently, the exhaust gases turn towards the closed end of the muffler 100 and pass through the holes in the second set of the flute-like tubes 18 and hit the baffle 10. Since the flute-like perforated tube 18 diameter is smaller than the inlet pipe 20, the impedance is further increased in a different frequency range as compared to first set of Flute-like tubes 16 due to their different length. Since the baffle 10 has no perforations in the lower half the gases

are redirected to towards the outlet pipe 30 to pass through the holes provided therein and to finally exit therethrough. Since the sound absorbing materials are surrounding the outlet pipe 30 at the exit region 32, the flow related noises are further suppressed.
Figure 11 shows the sound transmission loss (STL) in decibels for the muffler according to an earlier patent application by the same applicant for an automobile shown in Fig. 9. It is clear from this figure that the muffler is effective only for the higher range of frequencies, i.e. for 750 to 1600 Hz and for 2000 to 2500 Hz. It is not effective for lower frequency ranges.
Figure 12 shows the sound transmission loss (STL) in decibels for the muffler in accordance with the present invention as shown in Figures 1 and 10. This muffler is effective for the low frequency ranges, i.e 200 to 650 Hz which occurs in the form of noise generated due to combustion of diesel fuel. It is also effective for reducing the noise caused due to the flow of exhaust gases because of stage-wise reduction, first when entering the inlet pipe and then before finally leaving the muffler. Therefore, the muffler 100 in accordance with the present invention caters to reduction in noise for the complete range of sound frequencies.
Figure 13 shows a perspective detailed view of the second embodiment 110 of the muffler in accordance with the present invention, however without the outer casing thereof. It shows first end cover 2 and the second end cover 14 along with the baffle plates 4, 6, 8, 10 and 12 disposed between these at predetermined distances from each other along an axis X-X of the muffler 110. Two sets of flute-like perforated tubes (16, 16; 18, 18) are shown to pass through these baffle plates, as already described above. In contrast to the embodiment shown in Figures 1 and 8, in this embodiment, the outlet pipe 30 is configured straight to pass through the first end cover 2 in a longitudinal direction of the muffler 110. The baffle plate 10 has no holes on the lower half, however has holes in the upper half thereof. Sound absorbing materials M is shown to be packed between the second end cover 14 and the baffle 12 as well as between the first end cover 2 and the baffle plate 4.
Figure 14 shows another detailed view of the third embodiment of the muffler 120 in accordance with the present invention for the diesel generator sets. In this

embodiment, the outlet pipe 30 has a bend 32 outside the first end cover 2 to direct the outlet 30 of the attenuated exhaust gases just opposed to the incoming exhaust gases, which may be desirable in certain situations. The other components of the muffler are similar to the earlier two embodiments of the muffler in accordance with the present invention. WORKING PRINCIPLE OF THE INVENTION
The inlet pipe 20 guides the exhaust gases into the muffler chamber and to direct them towards the perforated baffle plate 12 disposed at the second end cover 14 of the muffler 100. A major portion of the exhaust gases return through first set of flutelike perforated tubes 16 and then through the sound absorbing material 28 through baffle 4 and again passes through the holes in the second set of flute-like tubes 18. The gases hits the baffle 10. Since the baffle 10 has no perforations in the lower half thereof, the gases are redirected to towards the outlet pipe 30 to pass through the holes provided therein and to finally exit there through. The sound absorbing materials 28 are surrounding the outlet pipe 30 before the exit region 32. The flow related noises are again suppressed at the outlet pipe. Since the diameters of the flute-like perforated tubes are substantially lower than the diameter of the inlet and outlet pipe, the impedance is increased, thus lowering the noise level in the low frequency range. Additionally when the gases hit the baffle plates 4 and 12, the interaction with sound absorbing material reduces the noise due to exhaust gas flow.
TECHNICAL ADVANTAGES & ECONOMIC SIGNIFICANCE
Some of the technical advantages of the integrated muffler with fluted tubes and packed with the sound absorbing materials, such as Glass wool in accordance with the present invention are as under:
- Reduces flow noise generated due to exhaust gas flow,
- Reduces fuel combustion- related noise,
- Concept can be adapted to any shape of the muffler,
- Facilitates a low exhaust back pressure,
- Overall sound quality is improved,
- Tuning of flute-like perforated tubes is possible according to the firing frequency of the diesel generator set, and
- Controlling the flow noise by using sound absorber materials.

Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", shall be understood to implies including a described element, integer or method step, or group of elements, integers or method steps, however, does not imply excluding any other element, integer or step, or group of elements, integers or method steps.
The use of the expression "a", "at least" or "at least one" shall imply using one or more elements or ingredients or quantities, as used in the embodiment of the disclosure in order to achieve one or more of the intended objects or results of the present invention.
The exemplary embodiments described in this specification are intended merely to provide an understanding of various manners in which this embodiment may be used and to further enable the skilled person in the relevant art to practice this invention. The description provided herein is purely by way of example and illustration. Although the embodiments presented in this disclosure have been described in terms of its preferred embodiments, the skilled person in the art would readily recognize that these embodiments can be applied with modifications possible within the spirit and scope of the present invention as described in this specification by making innumerable changes, variations, modifications, alterations and/or integrations in terms of materials and method used to configure, manufacture and assemble various constituents, components, subassemblies and assemblies, in terms of their size, shapes, orientations and interrelationships without departing from the scope and spirit of the present invention.
While considerable emphasis has been placed on the specific features of the preferred embodiment described here, it will be appreciated that many additional features can be added and that many changes can be made in the preferred embodiments without departing from the principles of the invention. These and other changes in the preferred embodiment of the invention will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.

We claim:
1. An integrated dissipative and reactive muffler with tuned flute-like perforated
tubes and sound absorbing materials, said muffler comprising:
at least one inlet pipe and at least one outlet pipe;
at least one set of flute-like perforated tubes each disposed parallel to each other and in-line with said inlet pipe and outlet pipe;
a first end cover on the inlet side and a second end cover closing one end of the muffler;
at least four of baffle plates disposed between said end covers configuring at least five hollow chambers therebetween and providing a circuitous path for allowing the exhaust gas flow through said muffler;
the first baffle plate being disposed near said first end cover forming a first hollow chamber and the fourth baffle plate being disposed near said second end cover forming a fifth hollow chamber; and
said first and said fifth chambers being packed with at least one sound absorbing material compacted in a predetermined density in the available hollow space in said respective chamber;
wherein, the length of said flute-like perforated tubes and said inlet and outlet pipes are respectively adapted to be tuned according to the firing frequency of the diesel generator set.
2. Muffler as claimed in claim 1, wherein the series of holes provided on each set of said flute-like perforated tubes, which are disposed facing each other and also running parallel to each other and at least a portion of said sets of tubes are spaced apart by means of a non-perforated and continuous partition to prevent flow of exhaust gas between through said partition.
3. Muffler as claimed in claim 1, wherein sound absorbing material of a predetermined density is packed within the available hollow space in a first chamber formed between the first end cover and the first perforated baffle plate disposed adjacent thereto.

4. Muffler as claimed in claim 1, wherein the sound absorbing material of a predetermined density is completely packed within the fifth chamber formed between the second end cover and the completely perforated baffle plate disposed adjacent thereto.
5. Muffler as claimed in claim 1, wherein said muffler is circular and comprises a corresponding first end cover with an aperture for introducing said inlet pipe and/or exiting said outlet pipe at one end and a second end cover to completely close the other end of said muffler, and said baffle plates also supporting said inlet pipe and outlet pipe in the corresponding apertures provided therein.
6. Muffler as claimed in claim 5, wherein said muffler is configured elliptical, rectangular, oval, square-shaped or in any other profiled hollow structural shape.
7. Muffler as claimed in claim 1, wherein said inlet pipe includes a plurality of holes on its surface exposed inside said muffler; said first set of tubes have a plurality of holes at one end thereof which is disposed near the inlet side end of said muffler and a single hole near the other end thereof, said first set of tubes completely disposed in-line with said inlet pipe; and the length of said first set of tubes and the length said inlet pipe are tuned according to the firing frequency of the respective diesel generator set.
8. Muffler as claimed in claim 1, wherein said outlet pipe includes a plurality of holes at least on a portion of its surface exposed inside said muffler; said second set of tubes have a plurality of holes approximately at the center thereof which is disposed near the inlet side end of said outlet pipe and a single hole near the other end thereof protruding out of the outlet pipe; the length of said second set of tubes and the length said outlet pipe are tuned according to the firing frequency of the respective diesel generator set.
9. Muffler as claimed in claim 1, wherein the baffle plate supporting said inlet pipe end adjacent the second end cover includes perforations only on the upper half portion thereof.

10. Muffler as claimed in claim 9, wherein the baffle plate disposed between the first baffle plate forming the inlet side chamber with the first end cover is packed with sound absorbing material and includes perforations throughout its surface for passage of exhaust gases.
11. Muffler as claimed in claim 9 to 10, wherein the chamber formed between the baffle plate supporting said inlet pipe-end adjacent the second end cover includes perforations only on the upper half portion thereof.
12. Muffler as claimed in claim 9 to 11, wherein chamber configured between the second baffle plate and the third baffle plate is sub-divided into an upper half chamber and a lower half-chamber by means of a non-perforated continuous partition disposed horizontally therebetween, said third baffle plate having perforations only on the upper half thereof disposed above said partition; and wherein said lower half chamber is further sub-divided into two smaller chambers by means of a half baffle plate having holes on surface thereof and also supporting said outlet pipe adjacent inlet end thereof.