Abstract:
An apparatus comprises a housing comprising an air inlet, an air outlet and a divider that divides the housing into first and second air passages. The housing comprises a resonance chamber for each air passage. Each resonance chamber comprises a port, and air waves enter each such resonance chamber through such port and resonate.

Description:
BACKGROUND 
   Computers generate noise. A source of noise, for example, is a fan. Noise generated by a computer is generally bothersome to a user of the computer. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a detailed description of exemplary embodiments of the invention, reference will now be made to the accompanying drawings in which: 
       FIG. 1  shows a portion of an apparatus employing a resonance chamber to reduce noise in accordance with various embodiments; 
       FIG. 2  shows another view of the apparatus for reducing noise in accordance with various embodiments; and 
       FIG. 3  shows an illustrative use of the apparatus of  FIGS. 1 and 2  to reduce noise in accordance with various embodiments. 
   

   NOTATION AND NOMENCLATURE 
   Certain terms are used throughout the following description and claims to refer to particular system components. As one skilled in the art will appreciate, computer companies may refer to a component by different names. This document does not intend to distinguish between components that differ in name but not function. In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . . .” Also, the term “couple” or “couples” is intended to mean either an indirect, direct, optical or wireless electrical connection. Thus, if a first device couples to a second device, that connection may be through a direct electrical or mechanical connection or through an indirect electrical or mechanical connection via other devices and connections. 
   DETAILED DESCRIPTION 
     FIG. 1  illustrates a portion  10  of a noise reduction device. The portion  10  shown in  FIG. 1  comprises a housing  11 . The housing  11  comprises a divider  12  that divides the housing  11  into two air passages  14  and  16 . Air flows through air passages  14  and  16  as indicated by arrows  30 ,  32 ,  34  and  36 . The divider  12  creates two air inlets  13  and  15  and two air outlets  17  and  19 . 
     FIG. 2  illustrates a complete noise reduction device  9  as comprising two portions  10  mated together. In at least some embodiments, each portion  10  is a mirror image of the other portion. When mated together, the portions  10  permit air to flow through the air passages created by the dividers  12 . The two portions  10  may be mated together by welding, adhesive or other suitable mechanisms. Each portion  10  may be formed as a unitary piece of material or combined together from separately manufactured pieces. 
   In the embodiments of  FIGS. 1 and 2 , the dividers  12  create two air passages  14  and  16 . In other embodiments, a divider may create more than two air passages (e.g., three air passages). In one embodiment, more than two dividers  12  may be provided in each portion  10  of the noise reduction device  9  to create three or more air passages. 
   In accordance with various embodiments, the housing  11  comprises at least one resonance chamber for each air passage  14 ,  16 . In the embodiments of  FIGS. 1 and 2 , the housing  11  comprises two resonance chambers for each air passage  14 ,  16 —resonance chambers  20  and  22  for air passage  14  and resonance chambers  24  and  26  for air passage  14 . Although two resonance chambers are provided for each air passage  14 ,  16  in the embodiment of  FIGS. 1 and 2 , any number (1 or more) of resonance chambers can be provided for each air passage. Accordingly, any number of air passages can be provided in housing  11  and any number of resonance chambers can be provided for each air passage. In some embodiments, at least one air passage may comprise a different number of resonance chambers than another air passage in housing  11 . 
   Each resonance chamber  20 ,  22 ,  24 , and  26  comprises a port (ports  21 ,  23 ,  25 , and  27 , respectively) into which acoustic waves enter. Once inside the resonance chamber, the air resonates when the frequencies of the acoustical waves from the noise sources are coincident with the natural frequencies of the resonance chambers. The resonances of the air inside the resonance chambers absorb the energy of the airwaves. As a result, the noise level associated with the airflow through the noise reduction device  9  is reduced as compared to what would be the case without the noise reduction device  9 . 
   The divider  12  comprises at least one resonance chamber, and in the illustrative embodiment of  FIGS. 1 and 2 , divider  12  comprises two resonance chambers  22 ,  24 —chamber  22  being provided for reducing the noise associated with air flowing through air passage  14  and chamber  24  being provided for reducing the noise associated air flowing through air passage  16 . 
   In accordance with various embodiments, the material of the housing defining the resonance chambers  20 ,  22 ,  24 , and  26  comprises metal (e.g., aluminum, magnesium, steel, etc.), carbon, or a sufficiently rigid plastic (e.g., glass-filled plastic). “Sufficiently rigid” means the resonance chamber is such that resonance of the airwaves inside the resonance chamber can occur with enough of a Q value (a larger Q value means the air resonance peak on a frequency response curve will be higher). 
   Each inlet  13 ,  15  of the air passages  14 ,  16  has a length L and a width W. In accordance with various embodiments, the ratio of L to W is substantially between 1 and 2. 
   The resonance frequency achieved by each resonance chamber is generally a function of the size of the ports  21 ,  23 ,  25 , and  27  of the resonance chambers (i.e., cross-sectional area of each port and the length of the port), as well as the interior volume of each resonance chamber. As such, the dimensions can be set so as to achieve the resonance frequency desired for a given application. In some embodiments, the size and thus the resonance frequency of one resonance chamber in the noise reduction device  9  may vary from the size and resonance frequency of another resonance chamber. If desired, all of the noise reduction device&#39;s resonance chambers may be tuned to a different frequency. 
     FIG. 3  illustrates an embodiment in which a heat exchanger  40  (a heat sink is also within the scope of the term heat exchanger) is used with the noise reduction device  9 . The heat exchanger  40  comprises a heat exchanging member  41  coupled to a heat pipe  42 . Heat from a heat producing component (e.g., processor in a computer) is channeled through the heat pipe to the heat exchanging member  41 . At least a portion of the heat exchanging member  41  is contained within the housing  11  of the noise reduction device  9 . As shown, portions  41   a  and  41   b  are provided in each air passage  14  and  16  of the noise reduction device  9 . The portions  41   a  and  41   b  comprise one or more fins. A hole  43   a  and  43   b  is provided through each set of fins  41   a  and  41   b , respectively. In various embodiments, the holes  43   a  and  43   b  are of the same size and align with resonance chamber ports  21 ,  23 ,  25 , and  27  of the various resonance chambers  20 ,  22 ,  24 , and  26  as shown. The holes  43   a  and  43   b  function as acoustic guide paths for the acoustical waves between each fin to the resonator ports  21 ,  23 ,  25 , and  27 . These holes  43   a  and  43   b  through the fins  41   a  and  41   b  can be circular in cross section, or can be another shape. 
   A fan  50  is also shown coupled to the combination of the noise reduction device  9  and heat exchanger  40 . Air from the fan  50  passes through the air passages of the noise reduction device  9 , is warmed by the heat of the heat exchanger  40 , and exits the noise reduction device&#39;s outlets  17 ,  19 . At the same time that the process of heat exchanging is occurring to help cool the heat-producing component coupled to the heat pipe  42 , noise produced by the fan  50  is reduced by the resonance of airwaves that occurs in one or more of the resonance chambers  20 ,  22 ,  24 , and  26  of the noise reduction device  9 . 
   In some embodiments, the noise reduction device  9  is usable with a computer, or other type of electronic system. The noise reduction device may be integrated into a portable or desktop computer. 
   The above discussion is meant to be illustrative of the principles and various embodiments of the present invention. Numerous variations and modifications will become apparent to those skilled in the art once the above disclosure is fully appreciated. It is intended that the following claims be interpreted to embrace all such variations and modifications.