Abstract:
Baffle assemblies capable of reducing noise transmission while admitting airflow are provided, for use in air passages such as an inlet or exit of a duct, housing, enclosure or partition. The baffle assemblies comprise S-shaped baffle sections comprising two curved baffle units arranged so as to provide an S-shaped passage. In some embodiments the curved baffle units include a curved portion and at least one flange portion. In some embodiments the curved baffle units have a shape capable of manufacture by a continuous extrusion process.

Description:
FIELD OF THE DISCLOSURE 
       [0001]    This disclosure relates to baffles capable of reducing noise transmission while admitting airflow, for use in air passages such as an inlet or exit of a duct, housing, enclosure or partition. 
       SUMMARY OF THE DISCLOSURE 
       [0002]    Briefly, the present disclosure provides a baffle assembly, such as for use in an inlet or exit of a duct, housing, enclosure or partition, comprising an S-shaped baffle section comprising two curved baffle units arranged so as to provide an S-shaped passage. Typically the baffle assembly comprises at least two S-shaped baffle sections each comprising two curved baffle units arranged so as to provide an S-shaped passage. In some embodiments, at least two S-shaped baffle sections are arranged front-to-back in an “SS” configuration, in some, at least two S-shaped baffle sections are arranged front-to-front in “SZ” configuration, and in some, at least two S-shaped baffle sections are arranged back-to-back in “ZS” configuration. In some embodiments, the curved baffle units bear an acoustically absorbing material, e.g., an acoustically absorbing non-woven material or an acoustically absorbing foam material. Typically the curved baffle units bear an acoustically absorbing material on their concave face, and in some embodiments the curved baffle units bear an acoustically absorbing material on their concave face only. In some embodiments the curved baffle units include a curved portion and at least one flange portion. In various embodiments, the curved portion may have a cross-section that is semi-circular, nearly semi-circular, parabolic, nearly parabolic, hyperbolic, or nearly hyperbolic. In some embodiments, the curved baffle units have a shape capable of manufacture by a continuous extrusion process. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0003]      FIG. 1  is a schematic cross-section of exemplary Baffle Assembly A according to the present disclosure, as described in the Examples herein. 
           [0004]      FIG. 2  is a schematic cross-section of exemplary Baffle Assembly B according to the present disclosure, as described in the Examples herein. 
           [0005]      FIGS. 3 a , 3 b  and 3 c    are schematic cross-sections of comparative baffle assemblies, as described in the Examples herein. 
           [0006]      FIGS. 4-7  are graphs representing insertion loss values measured at ⅓ octave intervals across the frequency range 100-20 kHz, for exemplary baffle assemblies according to the present disclosure and comparative baffle assemblies, as described in the Examples herein. 
       
    
    
     DESCRIPTION 
       [0007]    The present disclosure provides a sound absorbing apparatus for use in air inlet and outlets found in equipment such as generators sets, air compressors, HVAC ducting or housing/enclosures where air is moved in and out of inlets and exits and where reduction of noise level is required. The apparatus is a modular design consisting of the basic element, a “S” curved baffles supporting sound absorption material, that is stackable to accommodate any size of air inlet and outlets. The devise is scalable both in size and noise attenuation and accommodates many types of acoustic absorbing material to tune for precise sound attenuation. In some embodiments (such as depicted in  FIGS. 1 and 2 ), the “S” curved baffles ( 50 ) are arranged front-to-back in “SS” configurations (see, e.g., the “SSS” configuration of  FIG. 2 .). In some embodiments, the “S” curved baffles ( 10 ) are arranged front-to-front or back-to-back in “SZ” or “ZS” configurations (see, e.g., the “SZS” configuration of  FIG. 1 .). In some embodiments, “SS” and “SZ” configurations are combined. 
         [0008]    Typically each S-shaped baffle section comprises two curved baffle units. The curved baffle units include at least one curved portion. In some embodiments (such as depicted in  FIGS. 1 and 2 ) the curved baffle units ( 20 ) include a curved portion ( 30 ) and at least one flange portion ( 40 ). In some embodiments (such as depicted in  FIGS. 1 and 2 ) a single flange portion ( 40 ) bisects the curved portion ( 30 ). In some embodiments the curved portions are semi-circular in cross-section. In some embodiments the curved portions are nearly semi-circular in cross-section, departing from true circularity by no more than 10% over at least 80% of their curved portion. In some embodiments the curved portions are parabolic in cross-section. In some embodiments the curved portions are nearly parabolic in cross-section, departing from a true parabola by no more than 10% over at least 80% of their curved portion. In some embodiments the curved portions are hyperbolic in cross-section. In some embodiments the curved portions are nearly hyperbolic in cross-section, departing from a true hyperbola by no more than 10% over at least 80% of their curved portion. Baffles may be constructed of any suitable material, including metal, composite, polymer or ceramic materials or natural materials such as wood. In some embodiments baffles are made by a continuous extrusion process. In some embodiments baffles are made by a vacuum forming process. Baffles may be bare or may be covered with any suitable sound-absorbing or acoustic insulating material. 
         [0009]    Objects and advantages of this disclosure are further illustrated by the following examples, but the particular materials and amounts thereof recited in these examples, as well as other conditions and details, should not be construed to unduly limit this disclosure. 
       EXAMPLES 
       [0010]    The following abbreviations are used to describe the examples:
   dB: decibel   ft: foot   Hz: Hertz   mm: meter   mil: 10 −3  inches   mm: millimeter   μm: micrometer   
 
         [0018]    SPL: sound pressure level 
         [0019]    Acoustic Materials. 
         [0020]    H-100PSM: A 1 mil (25.4 μm) aluminized polyester film faced 1-inch (25.4 mm) acoustical foam, obtained under the trade designation “TUFCOTE H-100PSM” from Aearo Technologies, LLC, Indianapolis, Ind. 
         [0021]    TC2303: A 1.06-inch (26.9 mm) nonwoven acoustic insulating material, obtained under the trade designation “THINSULATE ACOUSTIC INSULATION TC2303” from 3M Company. 
         [0022]    MA-4700: A 1-inch (25.4 mm) nonwoven hydrophobic microfiber acoustical insulation mat, obtained under the trade designation “THINSULATE MARINE INSULATION MA4700” from 3M Company. 
         [0023]    The following baffle assemblies were constructed as follows: 
         [0024]    Baffle Assembly A A length of extruded semi-circular, 5 inch (127 mm) radius, 150 mil (3.81 mm), acrylonitrile butadiene styrene (ABS) extruded plastic, was cut into six, 24 inch (609.6 mm) elongate baffles. Bifurcating the concave face of each baffle was a flange, extending outward approximately 1-inch (25.4 mm) Baffles 1-6 were then cemented, by means of an adhesive acrylic foam tape, within a 24.5 by 32.0 by 15.5 inch (622.3 by 812.8 by 393.7 mm) plywood frame according to the following orientation: Baffles 1 and 2 were positioned centrally within the frame, with the collinearly opposed concave faces offset by 2.5 inches (63.5 mm) Baffles 3 and 4 were cemented, convex face to convex face opposite their respective flange, to Baffles 1 and 2, respectively. Baffles 5 and 6 were positioned with the concave face collinearly opposed, and offset by 2.5 inches (63.5 mm), to the concave face of Baffles 3 and 4, respectively. A plan view of the resulting baffle orientation is shown in  FIG. 1 . 
         [0025]    Baffle Assembly B 
         [0026]    A baffle assembly was constructed according to the procedure generally described in Baffle Assembly A, according to the following orientation: Baffles 1 and 2 were cemented centrally within the frame, with the collinearly opposed concave faces offset by 2.5 inches (63.5 mm) Baffles 3 and 4 were positioned diagonally opposite and then cemented, convex face to convex face and offset by 2.5 inches (63.5 mm), to Baffles 1 and 2, respectively. Baffles 5 and 6 were positioned with the concave face collinearly opposed, and offset by 2.5 inches (63.5 mm), to the concave face of Baffles 3 and 4, respectively. A plan view of the resulting baffle orientation is shown in  FIG. 2 . 
         [0027]    Comparative Baffle Assemblies C 1 , C2 and C3 
         [0028]    Plan views of Baffle Assemblies C1- C3 are illustrated in  FIGS. 3 a -3 c   , respectively. 
         [0029]    Baffle Assembly C1 
         [0030]    A baffle assembly was constructed according to the procedure generally described in Baffle Assembly A, wherein the six concave baffles were replaced with seven 24.5 by 10.0 inch by 150 mil (609.6 by 254.0 by 3.81 mm) plywood panels. The panels were cemented equidistantly within, and orientated parallel to, the sides of the frame. 
       Baffle Assembly C2 
       [0031]    A baffle assembly was constructed according to the general procedure described in C1, wherein the plywood panels were orientated at an angle of 20 degrees relative to those in C1. 
       Baffle Assembly C3 
       [0032]    A baffle assembly was constructed according to the general procedure described in C1, wherein the plywood panels were orientated at an angle of 30 degrees relative to those in C1. 
       Examples and Comparatives 
       [0033]    The baffle assemblies were subsequently covered with the acoustic materials described above by means of an adhesive acrylic foam tape, With respect to Baffle Assemblies A and B, the acoustic material was cemented to the concave face of the baffles, while for Comparative Baffle Assemblies C1-C3 the acoustic material cemented to both sides of the plywood panels. 
         [0000]    
       
         
               
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Sample 
                 Baffle Assembly 
                 Acoustic Material 
               
               
                   
                   
               
             
             
               
                   
                 Example 1 
                 A 
                 None 
               
               
                   
                 Example 2 
                 B 
                 None 
               
               
                   
                 Example 3 
                 A 
                 H-100PSM 
               
               
                   
                 Example 4 
                 B 
                 H-100PSM 
               
               
                   
                 Example 5 
                 A 
                 TC2303 
               
               
                   
                 Example 6 
                 B 
                 TC2303 
               
               
                   
                 Example 7 
                 A 
                 MA-4700 
               
               
                   
                 Example 8 
                 B 
                 MA-4700 
               
               
                   
                 Comparative A 
                 C1 
                 None 
               
               
                   
                 Comparative B 
                 C2 
                 None 
               
               
                   
                 Comparative C 
                 C3 
                 None 
               
               
                   
                 Comparative D 
                 C1 
                 H-100PSM 
               
               
                   
                 Comparative E 
                 C2 
                 H-100PSM 
               
               
                   
                 Comparative F 
                 C3 
                 H-100PSM 
               
               
                   
                 Comparative G 
                 C1 
                 TC2303 
               
               
                   
                 Comparative H 
                 C2 
                 TC2303 
               
               
                   
                 Comparative I 
                 C3 
                 TC2303 
               
               
                   
                 Comparative J 
                 C1 
                 MA-4700 
               
               
                   
                 Comparative K 
                 C2 
                 MA-4700 
               
               
                   
                 Comparative L 
                 C3 
                 MA-4700 
               
               
                   
                   
               
             
          
         
       
     
       Test Methods 
     Sound Attenuation 
       [0034]    The baffle assembly was installed in a wall cavity between a reverberation room and an anechoic room. The reverberation room was sound pressurized by a speakers providing balanced spectrum of “white noise” at approximately 104 dB SPL from 100-20 kHz. Sound attenuation (Insertion Loss) provided by the baffle assemblies were measured across a frequency range of 100 Hz to 20 kHz, at 1.5 meters from the baffle face, relative to the open wall cavity, according to the test procedure generally described in SAE J1400. Average Insertion Loss values are listed in Table 2. Insertion Loss values across the frequency range 100-20 kHz, measured at ⅓ octave intervals, are illustrated in  FIGS. 4-7 : 
         [0035]      FIG. 4 : No acoustic material 
         [0036]      FIG. 5 : Baffles covered with H-100SM 
         [0037]      FIG. 6 : Baffles covered with TC2303 
         [0038]      FIG. 7 : Baffles covered with MA-4700 
         [0000]    
       
         
               
               
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
               
                   
                   
                   
                 Average Insertion 
               
               
                   
                   
                   
                 Loss @ 1.5m 
               
               
                 Sample 
                 Baffle Assembly 
                 Baffle Covering 
                 SPL (dB) 
               
               
                   
               
             
             
               
                 Control 
                 None 
                 None 
                 15.5 
               
               
                 Example 1 
                 A 
                 None 
                 21.1 
               
               
                 Example 2 
                 B 
                 None 
                 21.1 
               
               
                 Example 3 
                 A 
                 H-100PSM 
                 35.0 
               
               
                 Example 4 
                 B 
                 H-100PSM 
                 35.0 
               
               
                 Example 5 
                 A 
                 TC2303 
                 43.2 
               
               
                 Example 6 
                 B 
                 TC2303 
                 42.5 
               
               
                 Example 7 
                 A 
                 MA-4700 
                 40.2 
               
               
                 Example 8 
                 B 
                 MA-4700 
                 39.9 
               
               
                 Comparative A 
                 C1 
                 None 
                 17.7 
               
               
                 Comparative B 
                 C2 
                 None 
                 16.2 
               
               
                 Comparative C 
                 C3 
                 None 
                 16.7 
               
               
                 Comparative D 
                 C1 
                 H-100PSM 
                 21.8 
               
               
                 Comparative E 
                 C2 
                 H-100PSM 
                 22.3 
               
               
                 Comparative F 
                 C3 
                 H-100PSM 
                 23.2 
               
               
                 Comparative G 
                 C1 
                 TC2303 
                 20.9 
               
               
                 Comparative H 
                 C2 
                 TC2303 
                 21.5 
               
               
                 Comparative I 
                 C3 
                 TC2303 
                 23.0 
               
               
                 Comparative J 
                 C1 
                 MA-4700 
                 19.9 
               
               
                 Comparative K 
                 C2 
                 MA-4700 
                 20.6 
               
               
                 Comparative L 
                 C3 
                 MA-4700 
                 22.6 
               
               
                   
               
             
          
         
       
     
         [0039]    Various modifications and alterations of this disclosure will become apparent to those skilled in the art without departing from the scope and principles of this disclosure, and it should be understood that this disclosure is not to be unduly limited to the illustrative embodiments set forth hereinabove.