Description:DESCRIPTION
Technical Field
[001] This disclosure relates generally to composite felts, and more particularly to a method of manufacturing composite felt and its composition thereof.

BACKGROUND
[002] In today's textile industries, we use materials like polyester and cotton to make yarn and composite felt that may be used for automotive interiors. However, making these end products is not only cost, but creates lot of leftover scraps, which may be termed as pre-consumer textile waste. Unfortunately, conventional methods to handle this waste are either inefficient or are environmentally unsafe. For example, the waste may be simply disposed of by being buried in landfills, thrown in rivers, or being burnt. All these methods end up polluting the environment (soil, water, and/or air).
[003] Therefore, there is a need to provide a cost-efficient and environmentally friendly method for producing composite felts for the automotive industry.
SUMMARY OF THE INVENTION
[004] In an embodiment, a method of manufacturing composite felts is disclosed. The method may include extracting poly-cotton waste from textile waste. The method may further include garneting the poly-cotton waste based on a pre-selected set of garneting parameters to produce garneted poly-cotton waste. The method may include mixing the garneted poly-cotton waste with recycled fibre material to produce mixed poly-cotton waste at a predefined temperature range. In an embodiment, the composition percentage of the garneted poly-cotton waste may be 65 % of the total composition of the mixed poly-cotton waste and the composition percentage of the recycled fibre material may be 35 % of the total composition of the mixed poly-cotton waste. The method may include carding the mixed poly-cotton waste based on a pre-selected set of carding parameters to produce a fibre web. The method may include needle punching the fibre web based on a pre-selected set of punching parameters to produce a composite felt.
[005] In another embodiment, a composite felt is disclosed. The composite felt may include 65% poly-cotton waste by weight of the composite felt. The composite felt may further include 35% recycled fibre material by weight of the composite felt. In an embodiment, the composite felt may include at least one salient feature. The at least one salient feature may include density of the composite felt being within a range of 200 Grams per Square Meter (GSM) to 800 GSM. The at least one salient feature may further include a sound absorption coefficient of the composite felt being within a range of 0.05 to 0.048 at a selected frequency range of 500 Hz to 5000 Hz. The at least one salient feature may further include sound transmission loss being within a range of 32 decibels at a frequency range of 500 Hz to 2000 Hz.
[006] In another embodiment, a vehicle component is disclosed. The vehicle component may include a composite felt that may include 65% poly-cotton waste by weight of the composite felt. The composite felt may further include 35% recycled fibre material by weight of the composite felt. In an embodiment, the composite felt may include at least one salient feature. The at least one salient feature may include density of the composite felt being within a range of 200 Grams per Square Meter (GSM) to 800 GSM. The at least one salient feature may further include a sound absorption coefficient of the composite felt being within a range of 0.05 to 0.048 at a selected frequency range of 500 Hz to 5000 Hz. The at least one salient feature may further include sound transmission loss being within a range of 32 decibels at a frequency range of 500 Hz to 2000 Hz.
[007] It is to be understood that both the foregoing general description and the following detailed descriptions are exemplary and explanatory only and are not restrictive of the invention, as claimed.
BRIEF DESCRIPTION OF THE DRAWING
[008] The accompanying drawings, which are incorporated in and constitute a part of this disclosure, illustrate exemplary embodiments and, together with the description, serve to explain the disclosed principles.
[009] FIG. 1 illustrates a flow diagram depicting various stages in the process for manufacturing a composite felt, in accordance with an embodiment of the present disclosure.
[010] FIG. 2 illustrates a flowchart of a method of manufacturing a composite felt, in accordance with an embodiment of the present disclosure.
[011] FIG. 3A is a plot depicting sound absorption coefficient of a composite felt within a given frequency range, in accordance with an embodiment of the present disclosure.
[012] FIG. 3B is a plot depicting sound transmission loss of a composite felt within a given frequency range, in accordance with an embodiment of the present disclosure.
DETAILED DESCRIPTION OF THE DRAWINGS
[013] The foregoing description has broadly outlined the features and technical advantages of the present disclosure in order that the detailed description of the disclosure that follows may be better understood. Additional features and advantages of the disclosure will be described hereinafter which forms the subject of the claims of the disclosure. It should be appreciated by those skilled in the art that the conception and specific embodiments disclosed may be readily utilized as a basis for modifying other devices, systems, assemblies, and mechanisms for conducting the same purposes of the present disclosure. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the scope of the disclosure as set forth in the appended claims. The novel features which are believed to be characteristics of the disclosure, to its device or system, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present disclosure.
[014] The terms “including”, “comprises”, “comprising”, “comprising of” or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a system or a device that comprises a list of components or steps does not include only those components or steps but may include other components or steps not expressly listed or inherent to such setup or device. In other words, one or more elements in a system or apparatus proceeded by “comprises… a” does not, without more constraints, preclude the existence of other elements or additional elements in the system or apparatus.
[015] Reference will now be made to the exemplary embodiments of the disclosure, as illustrated in the accompanying drawings. Wherever possible, the same numerals have been used to refer to the same or like parts. The following paragraphs describe the present disclosure with reference to FIGs. 1-3B. As summarized above, in one broad aspect, the present invention provides a method of manufacturing composite felts and its composition thereof.
[016] In textile industries, the materials like polyester and cotton are used to make textile yarn. However, these production processes generate a significant amount of leftover scrap, which is termed as pre-consumer textile waste. Conventional methods to handle this waste are either inefficient or environmentally unsafe. For example, the waste may be simply disposed of by being buried in landfills, thrown in rivers, or being burnt. All these methods end up polluting the environment (soil, water, and air). The present invention presents an innovative approach to manufacture composite felts by utilizing poly-cotton waste extracted from textile waste. This approach begins with extracting poly-cotton waste and garneting it to produce garneted poly-cotton waste. This garneted waste is then mixed with recycled fiber material. The mixed materials undergo carding to produce a fiber web. The fiber web is then needle punched to create a composite felt. The composition of the composite felt consists of 65% garneted poly-cotton waste and 35% recycled fiber material. Utilizing 65% textile waste in the manufacturing process of composite felt significantly reduces costs by maximizing the user of textile waste. Not only would it reduce the costs of a composite felt by utilizing the textile waste, but it could benefit the environment by reducing pollution and saving space in landfills. The composite felt have several applications one of them is making soft trim parts for the automotive industry. The soft trim parts consist of insulation, carpet, sun visors, etc. Furthermore, repurposing pre-consumer textile waste into composite felt aligns with sustainability goals by conserving natural resources and mitigating the current shortages of such resources. Additionally, this could decrease dependence on virgin fibers derived from fossil fuels.
[017] Referring now to FIG. 1, a flow diagram 100 depicting various stages in the process for manufacturing a composite felt, in accordance with an embodiment of the present disclosure.
[018] At 102, textile waste may be procured from textile industries and may include polyester waste, cotton waste, and impurities. At 104, the process of extraction may be performed on the textile waste to extract poly-cotton waste at 106. In the poly-cotton waste, the composition percentage of cotton waste may be 55% of the total composition of the poly-cotton waste and the composition percentage of polyester waste may be 45% of the total composition of the poly-cotton waste.
[019] At 108, the process of garneting may be performed on the poly-cotton waste based on a pre-selected set of garneting parameters. In an embodiment, the pre-selected set of garneting parameters may include, but is not limited to, a feed rate of the poly-cotton waste being selected from a range of 1.5 meters per minute to 3 meters per minute, a garneting roller speed being selected from a range of 150 Rounds Per Minute (RPM) to 250 RPM, a web thickness of the poly-cotton waste being selected from a range of 2 millimetres to 5 millimetres, a tension control being selected from a range of 150 newton per meter to 200 newtons per meter, an angle of carding element being selected from a range of 5 degrees to 15 degrees, a doffer speed being selected from a range of 15 RPM to 25 RPM, and a licker-in speed being selected from a range of 500 RPM to 600 RPM. As a result of the garneting, at 110, garneted poly-cotton waste may be produced. In the poly-cotton waste, the composition percentage of cotton waste may be 55% of the total composition of the garneted poly-cotton waste and the composition percentage of polyester waste may be 45% of the total composition of the garneted poly-cotton waste.
[020] At 112 the garneted poly-cotton waste may be mixed with recycled fibre material at a predefined temperature range to produce mixed poly-cotton waste at 114. The predefined temperature range may vary between 30°C to 40°C. In the mixed poly-cotto waste, the composition percentage of the garneted poly-cotton waste may be 65 % of the total composition of the mixed poly-cotton waste and the composition percentage of the recycled fibre material may be 35 % of the total composition of the mixed poly-cotton waste. In an embodiment, the recycled fibre material may be selected from polyester fibre, low melt fibre, or a combination thereof.
[021] Thereafter, at 116 the process of carding is performed on the mixed poly-cotton waste based on a pre-selected set of carding parameters to produce a fibre web at 118. The pre-selected set of carding parameters may include, but is not limited to, a feed rate of the mixed poly-cotton waste being selected from a range of 1.5 meters per minute to 3 metres per minute, a carding roller speed being selected from a range of 150 RPM to 250 RPM, a lick-in speed being selected from a range of 500 RPM to 600 RPM, a web thickness of the mixed poly-cotton waste being selected from a range of 2 millimetres to 5 millimetres, a tension control being selected from a range of 120 newton per meter to 150 newtons per meter, an airflow being selected from a range of 700 cubic metres per hour to 900 cubic meters per hour, and a suction control being selected from a range of 4 kilopascals to 8 kilopascals.
[022] The fibre web produced at 118 may then be needle punched at 120 based on a pre-selected set of punching parameters to produce a composite felt at 122. The pre-selected set of punching parameters may include, but are not limited to a needle density being selected from a range of 300 needles per square inch to 350 needles per square inch, a needle gauge being selected from a range of 5 needles per inch to 10 needles per inch, a needle punching depth being selected from a range of 3 millimetres to 5 millimetres, a feed rate of the fibre web being selected from a range of 10 metres per minute to 15 metres per minute, a web thickness of the fibre web being selected from a range of 2 millimetres to 5 millimetres, a machine speed being selected from a range of 400 strokes per minute to 600 strokes per minute, and a pressure setting being selected from a range of 150 kilo pascals to 250 kilo pascals.
[023] The composite felt thus created may have one or more salient features. The one or more salient features may include, but are not limited to density of the composite felt may be within a range of 200 Grams per Square Meter (GSM) to 800 GSM, a sound absorption coefficient of the composite felt 122 may be within a range of 0.05 to 0.48 at a selected frequency range of 500 Hertz (Hz) to 5000 Hz, and a sound transmission loss being within a range of 27 decibels to 37 decibels at a selected frequency range of 500 Hz to 2000 Hz.
[024] The composite felt created according to the flow diagram 100 offers a sustainable solution with better sound absorption coefficient, sound transmission loss, humidity absorption capacity, Noise, Vibration, and Harness (NVH) characteristics, flammability ratio, odor control, and resilience to both cold and high temperatures compared to current market alternatives. The composite felt created according to the flow diagram 100 offers a suitable solution for making vehicle components like, but not limited to, insulation, carpet, sun visors, etc.
[025] Referring now to FIG. 2, a flowchart of a method 200 of manufacturing a composite felt, in accordance with an embodiment of the present disclosure. It is to be noted that textile waste may be procured from textile industries. In an embodiment, the textile waste may include polyester waste, cotton waste, and impurities.
[026] At step 202, the process of extraction may be performed on the textile waste to extract poly-cotton waste. In the poly-cotton waste, the composition percentage of cotton waste may be 55 % of the total composition of the poly-cotton waste and the composition percentage of polyester waste may be 45 % of the total composition of the poly-cotton waste.
[027] Further at step 204, the process of garneting may be performed on the poly-cotton waste based on a pre-selected set of garneting parameters. In an embodiment, the pre-selected set of garneting parameters may include, but is not limited to, a feed rate of the poly-cotton waste being selected from a range of 1.5 meters per minute to 3 meters per minute, a garneting roller speed being selected from a range of 150 Rounds Per Minute (RPM) to 250 RPM, a web thickness of the poly-cotton waste (104) being selected from a range of 2 millimetres to 5 millimetres, a tension control being selected from a range of 150 newton per meter to 200 newtons per meter, an angle of carding element being selected from a range of 5 degrees to 15 degrees, a doffer speed being selected from a range of 15 RPM to 25 RPM, and a licker-in speed being selected from a range of 500 RPM to 600 RPM. As a result of the garneting, garneted poly-cotton waste may be produced. In the poly-cotton waste, the composition percentage of cotton waste may be 55% of the total composition of the garneted poly-cotton waste and the composition percentage of polyester waste may be 45% of the total composition of the garneted poly-cotton waste.
[028] Further at step 206, the garneted poly-cotton waste may be mixed with recycled fibre material at a predefined temperature range to produce mixed poly-cotton waste. The predefined temperature range may vary between 30°C to 40°C. In an embodiment, the composition percentage of the garneted poly-cotton waste may be 65 % of the total composition of the mixed poly-cotton waste and the composition percentage of the recycled fibre material may be 35 % of the total composition of the mixed poly-cotton waste. In an embodiment, the recycled fibre material may be selected from polyester fibre, low melt fibre, or a combination thereof.
[029] Further at step 208, the process of carding is performed on the mixed poly-cotton waste based on a pre-selected set of carding parameters to produce a fibre web. The pre-selected set of carding parameters may include, but is not limited to, a feed rate of the mixed poly-cotton waste being selected from a range of 1.5 meters per minute to 3 metres per minute, a carding roller speed being selected from a range of 150 RPM to 250 RPM, a lick-in speed being selected from a range of 500 RPM to 600 RPM, a web thickness of the mixed poly-cotton waste being selected from a range of 2 millimetres to 5 millimetres, a tension control being selected from a range of 120 newton per meter to 150 newtons per meter, an airflow being selected from a range of 700 cubic metres per hour to 900 cubic meters per hour, and a suction control being selected from a range of 4 kilopascals to 8 kilopascals.
[030] Further at step 210, the fibre web may then be needle punched based on a pre-selected set of punching parameters to produce a composite felt. The pre-selected set of punching parameters may include, but are not limited to a needle density being selected from a range of 300 needles per square inch to 350 needles per square inch, a needle gauge being selected from a range of 5 needles per inch to 10 needles per inch, a needle punching depth being selected from a range of 3 millimetres to 5 millimetres, a feed rate of the fibre web being selected from a range of 10 metres per minute to 15 metres per minute, a web thickness of the fibre web being selected from a range of 2 millimetres to 5 millimetres, a machine speed being selected from a range of 400 strokes per minute to 600 strokes per minute, and a pressure setting being selected from a range of 150 kilo pascals to 250 kilo pascals.
[031] The composite felt thus created may have one or more salient features. The one or more salient features may include but are not limited to, density of the composite felt may be within a range of 200 Grams per Square Meter (GSM) to 800 GSM., a sound absorption coefficient of the composite felt may be within a range of 0.05 to 0.48 at a selected frequency range of 500 Hertz (Hz) to 5000 Hz, and a sound transmission loss being within a range of 27 decibels to 37 decibels at a selected frequency range of 500 Hz to 2000 Hz.
[032] The composite felt thus created offers a sustainable solution with better sound absorption coefficient, sound transmission loss, humidity absorption capacity, Noise, Vibration, and Harness (NVH) characteristics, flammability ratio, odor control, and resilience to both cold and high temperatures compared to current market alternatives. The composite felt thus created offers a suitable solution for making vehicle components like, but not limited to, insulation, carpet, sun visors, etc.
[033] Referring now to FIG. 3A, a plot 300A depicting sound absorption coefficient of a composite felt within a given frequency range is illustrated, in accordance with an embodiment of the present disclosure. The plot 300A may include an x-axis and a y-axis. The x-axis may represent frequency, ranging from 500 Hertz (Hz) to 5000 Hz, while the y-axis may represent a sound absorption coefficient, measured on a scale from 0 to 1.
[034] As can be seen in the plot 300A, each data point corresponds to a sound absorption coefficient at a specific frequency of the composite felt (represented as modified sample) 302 and a conventional composite felt (represented as existing sample) 304. The plot 300A reveals a clear trend where the sound absorption coefficient of the modified sample 302 may exhibit a higher sound absorption coefficient compared to the existing sample 304. In an embodiment, the sound absorption coefficient of the modified sample 302 (i.e., the composite felt of the present invention) may be within a range of 0.05 to 0.48 at a selected frequency range of 500 Hertz (Hz) to 5000 Hz.
[035] Referring now to FIG. 3B, a plot 300B depicting sound transmission loss of a composite felt within a given frequency range is illustrated, in accordance with an embodiment of the present disclosure. The plot 300B may include an x-axis and a y-axis. The x-axis may represent frequency, ranging from 500 Hertz (Hz) to 5000 Hz, while the y-axis may represent a sound transmission loss, measured in decibels.
[036] As can be seen in the plot 300B, each data point corresponds to sound transmission loss at a specific frequency of the composite felt (represented as modified sample) 302 and a conventional composite felt (represented as existing sample) 304. The plot 300A reveals a clear trend the modified sample 302 (i.e., the composite felt of the present invention) demonstrates a consistent STL performance, with values ranging from 27 decibels to 37 decibels across the frequency range of 500 Hertz (Hz) to 2000 Hz, while keeping the acoustic properties similar from 2000 Hz to 5000 Hz.
[037] Thus, the disclosed method and composition reduces production costs of the composite felt, thereby overcoming one of the drawbacks of existing composite felts, i.e., high cost. As a result, the overall cost of the end products incorporating these composite felts is also substantially reduced. This increases the accessibility and affordability of these end products for consumers or manufacturers. Further, the disclosed method and composition ensures efficient handling of pre-consumer textile waste from the textile industry, which currently lacks organized methods for management.
To this end, pre-consumer textile waste is transformed into eco-friendly composite felt that is suitable for automotive soft trims such as insulation, carpeting, and sun visors.
[038] Though, pre-consumer textile waste is utilized to produce the composite felt, the use of current tools and procedures to transform the waste into composite felt with diverse weights, ensures that all quality standards that are required for various automotive components are met. Thus, by leveraging innovative mixing techniques to incorporate textile waste, low-melt fibers, and recycled polyester fibers in appropriate ratios, various salient features of the composite felt meet automotive requirements and standards. Other ancillary benefits of the disclosed composite felt include reduced usage of fossil fuel-based material, direct material cost savings, and environmental sustainability. To achieve environmental sustainability, the need for chemical, thermal, and mechanical mixing processes is eliminated. This reduces environmental impact.
[039] As will be appreciated by those skilled in the art, the design described in the various embodiments discussed above are not routine, or conventional, or well-understood in the art. The techniques discussed above provide the integration of flow valves and the replacement of the pressure switch with a more advanced pressor sensor.
[040] In light of the above-mentioned advantages and the technical advancements provided by the disclosed method and system, the claimed steps as discussed above are not routine, conventional, or well understood in the art, as the claimed steps enable the following solutions to the existing problems in conventional technologies. Further, the claimed steps bring an improvement in the functioning of the device itself as the claimed steps provide a technical solution to a technical problem.
[041] The specification has described method of manufacturing composite felt and its composition thereof. The illustrated steps are set out to explain the exemplary embodiments shown, and it should be anticipated that ongoing technological development will change the manner in which particular functions are performed. These examples are presented herein for purpose of illustration, and not limitation. Further, the boundaries of the functional building blocks have been arbitrarily defined herein for the convenience of the description. Alternative boundaries can be defined so long as the specified functions and relationships thereof are appropriately performed. Alternatives (including equivalents, extensions, variations, deviations, etc., of those described herein) will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. Such alternatives fall within the scope and spirit of the disclosed embodiments.
[042] It is intended that the disclosure and examples be considered as exemplary only, with a true scope of disclosed embodiments being indicated by the following claims.
, Claims:1. A method (200) of manufacturing composite felts, the method (200) comprising:
extracting (202) poly-cotton waste from textile waste;
garneting (204) the poly-cotton waste (106) based on a pre-selected set of garneting parameters to produce garneted poly-cotton waste;
mixing (206) the garneted poly-cotton waste with recycled fibre material to produce mixed poly-cotton waste at a predefined temperature range,
wherein the composition percentage of the garneted poly-cotton waste is 65 % of the total composition of the mixed poly-cotton waste and the composition percentage of the recycled fibre material is 35% of the total composition of the mixed poly-cotton waste;
carding (208) the mixed poly-cotton waste based on a pre-selected set of carding parameters to produce a fibre web; and
needle punching (210) the fibre web based on a pre-selected set of punching parameters to produce a composite felt.

2. The method (200) as claimed in claim 1, wherein the composition percentage of cotton waste is 55% of the total composition of the poly-cotton waste and the composition percentage of polyester waste is 45% of the total composition of the poly-cotton waste.

3. The method (200) as claimed in claim 1, wherein the recycled fibre material is selected from polyester fibre, low melt fibre, or a combination thereof.

4. The method (200) as claimed in claim 1, wherein the predefined temperature range varies between 30°C to 40°C.

5. The method (200) as claimed in claim 1, wherein the composite felt comprises at least one salient feature.

6. The method (200) as claimed in claim 5, wherein the at least one salient feature comprises:
density of the composite felt being within a range of 200 Grams per Square Meter (GSM) to 800GSM.

7. The method (200) as claimed in claim 5, wherein the at least one salient feature comprises:
a sound absorption coefficient of the composite felt being within a range of 0.05 to 0.48 at a selected frequency range of 500 Hertz (Hz) to 5000 Hz.

8. The method (200) as claimed in claim 5, wherein the at least one salient feature comprises:
sound transmission loss being within a range of 27 decibels to 37 decibels at a selected frequency range of 500 Hz to 2000 Hz.

9. The method (200) as claimed in claim 1, wherein the pre-selected set of garneting parameters comprises:
a feed rate of the poly-cotton waste being selected from a range of 1.5 meters per minute to 3 meters per minute;
a garneting roller speed being selected from a range of 150 Rounds Per Minute (RPM) to 250 RPM;
a web thickness of the poly-cotton waste being selected from a range of 2 millimetres to 5 millimetres;
a tension control being selected from a range of 150 newton per meter to 200 newtons per meter;
an angle of carding element being selected from a range of 5 degrees to 15 degrees;
a doffer speed being selected from a range of 15 RPM to 25 RPM; and
a licker-in speed being selected from a range of 500 RPM to 600 RPM.

10. The method (200) as claimed in claim 1, wherein the pre-selected set of carding parameters comprises:
a feed rate of the mixed poly-cotton waste being selected from a range of 1.5 meters per minute to 3 metres per minute;
a carding roller speed being selected from a range of 150 RPM to 250 RPM;
a lick-in speed being selected from a range of 500 RPM to 600 RPM;
a web thickness of the mixed poly-cotton waste being selected from a range of 2 millimetres to 5 millimetres;
a tension control being selected from a range of 120 newton per meter to 150 newtons per meter;
an airflow being selected from a range of 700 cubic metres per hour to 900 cubic meters per hour; and
a suction control being selected from a range of 4 kilopascals to 8 kilopascals.

11. The method (200) as claimed in claim 1, wherein the pre-selected set of punching parameters comprises:
a needle density being selected from a range of 300 needles per square inch to 350 needles per square inch;
a needle gauge being selected from a range of 5 needles per inch to 10 needles per inch;
a needle punching depth being selected from a range of 3 millimetres to 5 millimetres;
a feed rate of the fibre web being selected from a range of 10 metres per minute to 15 metres per minute;
a web thickness of the fibre web being selected from a range of 2 millimetres to 5 millimetres;
a machine speed being selected from a range of 400 strokes per minute to 600 strokes per minute; and
a pressure setting being selected from a range of 150 kilo pascals to 250 kilo pascals.

12. A composite felt comprising:
65% poly-cotton waste by weight of the composite felt; and
35% recycled fibre material by weight of the composite felt,
wherein the composite felt comprises at least one salient feature comprising:
density of the composite felt being within a range of 200 Grams per Square Meter (GSM) to 800 GSM,
a sound absorption coefficient of the composite felt being within a range of 0.05 to 0.48 at a selected frequency range of 500 Hz to 5000 Hz, and
sound transmission loss being within a range of 27 decibels to 37 decibels at a frequency range of 500 Hz to 2000 Hz.

13. A vehicle component comprising:
a composite felt, wherein the composite felt comprises:
65% poly-cotton waste by weight of the composite felt; and
35% recycled fibre material by weight of the composite felt,
wherein the composite felt comprises at least one salient feature comprising:
density of the composite felt being within a range of 200 Grams per Square Meter (GSM) to 800 (GSM),
a sound absorption coefficient of the composite felt being within a range of 0.05 to 0.48 at a selected frequency range of 500 Hz to 5000 Hz, and
sound transmission loss being within a range of 27 decibels to 37 decibels at a selected frequency range of 500 Hz to 2000 Hz.