DESC:CROSS REFERENCE TO RELATED APPLICATION
This Application is based on and derives the benefit of Indian Provisional Application 202141036188 filed on 10th August 2021, the contents of which are incorporated herein by reference

TECHNICAL FIELD
[001] The embodiments herein generally relate to air intake systems in engines and more particularly, to a compact acoustic attenuation device for attenuating broad frequency band of noise in an air intake line of the engine, even when the length of an air intake duct is shorter and it does not have any straight profile.

BACKGROUND
[002] Generally, an engine intake system is used for inducting intake air into combustion chambers of an engine. An efficient air intake system allows for clean and continuous airflow into the engine, thereby achieving more power, torque and better fuel economy for the vehicle. However, a noise may be generated in the air intake line during the air intake process. Also, noise pulses generated during engine combustion and the noise induced by turbocharger compressor, propagate through air intake line. This noise may be transmitted to vehicle’s passenger cabin through various transfer paths. For example, the noises may resonate through various intake conduits and be transferred through various medium to the vehicle. The vehicle driver and/or passengers may find this noise displeasing. Consequently, customer satisfaction may be decreased.
[003] Usually, sound absorbers or acoustic attenuators, are used for reducing the noise generated during the air intake process. For attenuating noise at single frequency band, typically a Helmholtz resonator or a quarter wave tube resonator is used in air intake line. For attenuating noise in multiple frequency bands, typically a broadband resonator, having multiple resonating chambers, is used in air intake line. Conventional broadband acoustic attenuators are attached around air intake duct on either suction or on discharge side of turbocharger for attenuating the noise during the air intake process. This type of inline acoustic attenuators, resonating chambers are placed one after another along the length of the intake line and require intake duct to have fairly straight profile. This poses a challenge for mounting these types of acoustic attenuators when the length of the air intake duct in the air intake system is shorter and does not have adequate straight portion.
[004] Therefore, there exists a need for an acoustic attenuation device which is compact in size and is capable of attenuating the noise even when length of the intake air duct of the air intake system is shorter and there is no adequate straight length available in duct. Further, there exists a need for a modular acoustic attenuation device for attenuating noise in an air intake line of an internal combustion engine, which obviates the aforementioned drawbacks.

OBJECTS
[005] The principal object of embodiments herein is to provide a compact acoustic attenuation device for attenuating broad frequency band of noise in an air intake line of an internal combustion (IC) engine even when the length of an air intake duct is shorter.
[006] Another object of embodiments herein is to provide a compact acoustic attenuation device which can be fitted to an air intake duct wherein there is no straight length available in intake duct.
[007] Another object of embodiments herein is to provide a modular acoustic attenuation device having multiple resonating chambers which attenuate intake noise in defined frequency bands without affecting air flow path in a curved air intake line.
[008] Another object of embodiments herein is to provide the acoustic attenuation device with integrated multiple quarter wave tube resonators without affecting air flow path in a curved air intake line.
[009] Another object of embodiments herein is to provide the compact acoustic attenuation device for attenuating broad frequency band of noise without restricting air flow to engine thereby without compromising engine performance.
[0010] Another object of embodiments herein is to provide the noise attenuation device, which enhances noise, vibration and harshness (NVH) characteristics of the vehicle.
[0011] Another object of an embodiment herein is to provide the modular acoustic attenuation device, which is inexpensive and easy to manufacture.
[0012] Another object of an embodiment herein is to provide the modular acoustic attenuation device in which different variations of resonating conduits can be devised without changing outer casings (cover) to attenuate intake air noise in different set of frequency bands generated by another variant of engine or turbocharger.
[0013] These and other objects of embodiments herein will be better appreciated and understood when considered in conjunction with following description and accompanying drawings. It should be understood, however, that the following descriptions, while indicating embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications.

BRIEF DESCRIPTION OF DRAWINGS
[0014] The embodiments are illustrated in the accompanying drawings, throughout which like reference letters indicate corresponding parts in various figures. The embodiments herein will be better understood from the following description with reference to the drawings, in which:
[0015] Fig. 1 illustrates an air intake duct with complete air intake system without the acoustic attenuator, where an intake air duct has short length and does not have straight profile, due to packaging constraints of the vehicle, around which conventional broadband resonator cannot be adopted;
[0016] Fig. 2 depicts cross-sectional view of the intake air duct before the introduction of acoustic attenuating device;
[0017] Fig. 3 depicts cross-sectional view of the air intake duct with a conventional Helmholtz resonator located at curved portion of intake duct which can attenuate noise only at one particular frequency band;
[0018] Fig. 4 illustrates an air intake duct having adequate straight length wherein a conventional multi-chamber resonator has been incorporated to attenuate noise corresponding to multiple frequency bands;
[0019] Fig. 5 depicts perspective view of the air intake duct after the introduction of the acoustic attenuating device at curved portion of air intake duct without restricting air flow to the engine, according to embodiments as disclosed herein;
[0020] Fig. 6 and 7 depict front view and exploded views of the acoustic attenuating device which includes multiple frequency resonating chambers and multi quarter wave resonating tubes designed by integrating three injection molded plastic components, according to embodiments as disclosed herein; and
[0021] Fig. 8 depicts a color plot showing relationship among intake orifice noise, frequency and time and a graph plot between intake orifice noise in 500-3000Hz frequency band and time. Plots show reduction in air intake orifice noise due to introduction of the acoustic attenuating device, according to embodiments as disclosed herein.

DETAILED DESCRIPTION
[0022] The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
[0023] The embodiments herein achieve an acoustic attenuation device for attenuating broad frequency band of noise in an air intake line of an internal combustion (IC) engine even when the length of an air intake duct is shorter and does not have adequate straight profile to accommodate conventional multi-chamber resonator. Referring now to the drawings Figs 1 through 8, where similar reference characters denote corresponding features consistently throughout the figures, there are shown embodiments.
[0024] Fig. 5 depicts perspective view of the air intake duct (10) after the introduction of the acoustic attenuating device (100) at non-linear section (curved portion) (10C) of air intake duct (10) without restricting air flow to the engine, according to embodiments as disclosed herein. Fig. 6 shows perspective view of the intake air duct (10) after the introduction of the noise attenuating device (100), according to embodiments as disclosed herein. In an embodiment, the acoustic attenuation device (100) includes a non-linear acoustic resonator (102) and a cover (104). The non-linear acoustic resonator (102) is adapted to attenuate noise of the intake air of various frequencies. The non-linear acoustic resonator (102) is adapted to attenuate intake air noise, vibration and harness (NVH) at a specific frequency by inhibiting pressure wave harmonics, which interacts with sound pressure waves propagating through air intake line thereby attenuating intake noise generated by engine combustion or noise induced by turbocharger. The non-linear acoustic resonator (102) adapted to be positioned at a non-linear section ((10C), (as shown in fig. 6)) of an air intake duct (10). The non-linear acoustic resonator (102) acts as a part of the non-linear section (10C) of the air intake duct (10). For the purpose of this description and ease of understanding, the non-linear section (10C) of the air intake duct (10) is considered to be a curved section of the air intake duct (10). The non-linear acoustic resonator (102) includes a plurality of acoustic frequency resonating perforations (102A, 102B, 102C, 102D), a plurality of quarter wave resonating portions (102QP) and a plurality of walls (102W). The plurality of walls (102W) extends from the non-linear acoustic resonator (102) and is engaged with the cover (104) to define a plurality of acoustic frequency resonating chambers ((102RA, 102RB, 102RC, 102RD) (as shown in fig. 7)). The acoustic frequency resonating perforations (102A, 102B, 102C and 102D) and the quarter wave resonating portions (102QP) are adapted to attenuate the intake air noise in defined frequency bands. The plurality of acoustic frequency resonating perforations (102A, 102B, 102C, 102D) includes a plurality of first acoustic frequency resonating perforations (102A), a plurality of second acoustic frequency resonating perforations (102B), a plurality of third acoustic frequency resonating perforations (102C) and a plurality of fourth acoustic frequency resonating perforations (102D). The plurality of acoustic frequency resonating chambers (102RA, 102RB, 102RC, 102RD) includes a first acoustic frequency resonating chamber (102RA) corresponding to the first acoustic frequency resonating perforations (102A), a second acoustic frequency resonating chamber (102RB) corresponding to the second acoustic frequency resonating perforations (102B), a third acoustic frequency resonating chamber (102RC) corresponding to the third acoustic frequency resonating perforations (102C), a fourth acoustic frequency resonating chamber (102RD) corresponding to the fourth acoustic frequency resonating perforations (102D). A volume of acoustic frequency resonating chambers (102RA, 102RB, 102RC, 102RD) is not same.
[0025] In an embodiment, the plurality of quarter wave resonating portions (102QP) defines a plurality of quarter wave chambers (102QC). Each quarter wave resonating portion (102QP) has a predefined length. A volume of each of the quarter wave resonating portion (102QP) is not same. The quarter wave resonating portions (102QP) are adapted to attenuate intake air noise of predefined frequencies. Each quarter wave resonating portion (102QP) defines a rectangular shape or polygonal shape. Each quarter wave resonating portions (102QP) is at least a cavity. The cover (104) mounted onto the air intake duct (10) to conceal the non-linear noise resonator (102).
[0026] Number and size of acoustic frequency resonating perforations (102A, 102B, 102C and 102D), volume of each acoustic frequency resonating chambers (102RA, 102RB, 102RC and 102RD), size, number and length of quarter wave resonating portions (102QP) can be fine-tuned to get a specific design of non-linear acoustic resonator (102) to effectively attenuate air intake noise for a specific application.
[0027] Fig. 8 depicts a color plot and graph showing relationship among intake orifice noise and frequency in 500-3000Hz frequency band. From fig. 8, it evident that air intake noise has reduced significantly due to introduction of the noise attenuating device (100).
[0028] The technical advantages of the acoustic attenuating device (100) are as follows. The acoustic attenuation device is used attenuating broad frequency band of noise in the air intake line of engine even when the length of an air intake duct is shorter, and it does not have any straight profile. Flow path of air is not affected with introduction of resonator and hence there is no significant impact on air intake depression, engine performance and fuel economy. By suitably tuning the design of resonating conduit, intake noise in desired frequency bands can be attenuated. Because of modularity in design of the acoustic attenuation device, only by changing design of resonating conduit, while keeping outer casings same, device can be used for a different variant of engine or turbocharge which has different noise characteristics. The acoustic attenuation device enhances noise, vibration and harness (NVH) of the vehicle. The modular acoustic attenuation device includes multiple resonating chambers which attenuate intake noise in defined frequency bands without affecting air flow path in a curved air intake line. The acoustic attenuation device is integrated with multiple quarter wave tube resonators without affecting air flow path in a curved air intake line. The compact acoustic attenuation device for attenuating broad frequency band of noise without restricting air flow to engine thereby without compromising engine performance. The acoustic attenuation device, which enhances noise, vibration and harshness (NVH) characteristics of the vehicle. The modular acoustic attenuation device is inexpensive and easy to manufacture.
[0029] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modifications within the spirit and scope of the embodiments as described herein.
,CLAIMS:We claim,
1. An acoustic attenuating device (100) in an air intake line of an engine, said acoustic attenuating device (100) comprising:
a non-linear acoustic resonator (102) adapted to be positioned at a non-linear section (10C) of an air intake duct (10); and
a cover (104) mounted onto the air intake duct (10) to conceal said non-linear acoustic resonator (102).

2. The acoustic attenuating device (100) as claimed in claim 1, wherein said non-linear acoustic resonator (102) includes,
a plurality of acoustic frequency resonating perforations (102A, 102B, 102C, 102D);
a plurality of quarter wave resonating portions (102QP); and
a plurality of walls (102W) extending therefrom and are engaged with said cover (104) to define a plurality of acoustic frequency resonating chambers (102RA, 102RB, 102RC, 102RD).

3. The acoustic attenuating device (100) as claimed in claim 1, wherein said non-linear acoustic resonator (102) acts as a part of the non-linear section (10C) of the air intake duct (10);
the non-linear section (10C) of the air intake duct (10) is a curved section of the air intake duct (10); and
said non-linear acoustic resonator (102) is adapted to attenuate noise of the intake air.

4. The acoustic attenuating device (100) as claimed in claim 2, wherein said plurality of acoustic frequency resonating perforations (102A, 102B, 102C, 102D) includes,
a plurality of first acoustic frequency resonating perforations (102A);
a plurality of second acoustic frequency resonating perforations (102B);
a plurality of third acoustic frequency resonating perforations (102C); and
a plurality of fourth acoustic frequency resonating perforations (102D).

5. The acoustic attenuating device (100) as claimed in claim 4, wherein said plurality of acoustic frequency resonating chambers (102RA, 102RB, 102RC, 102RD) includes,
a first acoustic frequency resonating chamber (102RA) corresponding to said first acoustic frequency resonating perforations (102A);
a second acoustic frequency resonating chamber (102RB) corresponding to said second acoustic frequency resonating perforations (102B);
a third acoustic frequency resonating chamber (102RC) corresponding to said third acoustic frequency resonating perforations (102C); and
a fourth acoustic frequency resonating chamber (102RD) corresponding to said fourth acoustic frequency resonating perforations (102D).

6. The acoustic attenuating device (100) as claimed in claim 2, wherein said plurality of quarter wave resonating portions (102QP) defines a plurality of quarter wave chambers (102QC);
each of said quarter wave resonating portion (102QP) has a predefined length;
a volume of each of said quarter wave resonating portion (102QP) is not same;
each of said quarter wave resonating portion (102QP) is adapted to attenuate intake air noise of a predefined frequency.

7. The acoustic attenuating device (100) as claimed in claim 6, wherein said non-linear acoustic resonator (102) is adapted to attenuate intake air noise, vibration and harness (NVH) at a specific frequency by inhibiting pressure wave harmonics, which interacts with sound pressure waves propagating through air intake line thereby attenuating intake noise generated by engine combustion or noise induced by turbocharger.

8. The acoustic attenuating device (100) as claimed in claim 2, wherein said acoustic frequency resonating perforations (102A, 102B, 102C and 102D) and said quarter wave resonating portions (102QP) are adapted to attenuate the intake air noise in defined frequency bands.

9. The acoustic attenuating device (100) as claimed in claim 2, wherein each of said quarter wave resonating portion (102QP) defines a rectangular shape or polygonal shape;
each of said quarter wave resonating portions (102QP) is at least a cavity;

10. The acoustic attenuating device (100) as claimed in claim 2, wherein a volume of acoustic frequency resonating chambers (102RA, 102RB, 102RC, 102RD) is not same.