US20100258377A1

US20100258377A1 - Acoustic cooling muffler for computing systems

Info

Publication number: US20100258377A1
Application number: US12/422,843
Authority: US
Inventors: Kevin M. Cash; Steven E. Howell; Robert M. Lindsay; Tomothy A. Meserth; Gerard F. Muenkel
Original assignee: International Business Machines Corp
Current assignee: International Business Machines Corp
Priority date: 2009-04-13
Filing date: 2009-04-13
Publication date: 2010-10-14

Abstract

An acoustic cooling apparatus for a computing system, includes a cooling muffler comprising sidewalls and an endwall, the sidewalls being substantially parallel to each other, each sidewall being substantially perpendicular to the endwall at one end, the walls forming an enclosure having an open end opposing the endwall. Each sidewall includes an exhaust opening. At least a portion of the interior of each wall of the enclosure being covered by sound absorbing material for attenuating air cooling sound.

Description

BACKGROUND

1. Field of the Invention
The present invention relates generally to acoustic systems, and in particular, to acoustics systems for computing machines.
2. Background Information
Computing systems with rack drawers for computing devices are designed primarily for data center environments. As such, computing systems require a significant amount of airflow in order to maintain an acceptable internal operating temperature. However, air moving devices, such as fans and blowers, generate a level of noise that is unacceptable in an office environment compared with data centers.

BRIEF SUMMARY

An acoustic cooling apparatus for a computing system. One embodiment of the acoustic cooling apparatus comprises a cooling muffler comprising sidewalls and an endwall, the sidewalls being substantially parallel to each other, each sidewall being substantially perpendicular to the endwall at one end, the walls forming an enclosure having an open end opposing the endwall. Each sidewall includes an exhaust opening. At least a portion of the interior of each wall of the enclosure is covered by sound absorbing material for attenuating air cooling sound.
Substantially the entire interior of each wall of the enclosure may be covered by sound absorbing material selected based on the frequency of air cooling sound being attenuated. The sound absorbing material may be selected in thickness, porosity and material type for attenuating cooling sound entering said open end, allowing the cooling sound energy to penetrate the sound absorbing material, compressing the sound absorbing material at a microscopic level. The sound absorbing material may be selected to allow the cooling sound energy to penetrate into the sound absorbing material, causing recoil of the sound absorbing material and pulling back on the sound absorbing material being compressed by the sound energy, thereby canceling some of the sound energy by converting it to heat.
The acoustic cooling apparatus may comprise four rectangular sidewalls and a square endwall, the sidewalls being substantially parallel to each other, each sidewall being substantially perpendicular to the endwall at one end and connected to a side of the endwall square, the walls forming an enclosure having a square open end opposing the endwall.
Other aspects and advantages of the present invention will become apparent from the following detailed description, which, when taken in conjunction with the drawings, illustrate by way of example the principles of the invention.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

For a fuller understanding of the nature and advantages of the invention, as well as a preferred mode of use, reference should be made to the following detailed description read in conjunction with the accompanying drawings, in which:

FIG. 1 illustrates an acoustic device connected to an air moving noise generating device;

FIG. 2 illustrates a perspective view of the acoustic device;

FIG. 3 illustrates another perspective view of the acoustic device;

FIG. 4 illustrates a representation of air flow and sound attenuation within the acoustic device.

DETAILED DESCRIPTION

The following description is made for the purpose of illustrating the general principles of the invention and is not meant to limit the inventive concepts claimed herein. Further, particular features described herein can be used in combination with other described features in each of the various possible combinations and permutations. Unless otherwise specifically defined herein, all terms are to be given their broadest possible interpretation including meanings implied from the specification as well as meanings understood by those skilled in the art and/or as defined in dictionaries, treatises, etc.
The description may disclose several preferred embodiments of an acoustic cooling apparatus as well as operation and/or component parts thereof. While the following description will be described in terms of acoustic devices in computing systems, it should be kept in mind that the teachings herein may have broad application to all types of systems, devices and applications.
One embodiment involves an acoustic apparatus that blocks the direct line of sight to noise generating devices while presenting a low impedance plenum with sufficient air flow. Referring to FIG. 1, one implementation comprises an acoustic cooling muffler door 1 which diverts air exhaust in four different directions to accommodate inadvertent blockage of one side or top vent area. In FIG. 1, the muffler door 1 is shown attached to a device (rack) 1 a which includes an air moving device that generates noise. The muffler door 1 substantially blocks the direct line of sight to the noise generating device.
FIG. 2 illustrates a perspective view of the muffler door 1, showing the interior area of the muffler door 1. The interior surface opposite the noise generating air moving device 1 a is covered with sound absorbing material such as planar acoustic foam layer 4 (e.g., 1.5 inch thick) that is appropriate to the frequency of the noise being attenuated. The cooling muffler door 1 comprises rectangular sidewalls 3 b and a rectangular (preferably square) endwall 6, the sidewalls 3 b substantially parallel to each other and substantially perpendicular to the endwall 6, forming an enclosure with an rectangular opening 6 a facing the endwall 6.
The interior side surfaces (i.e., interior of sidewalls 3 b and endwall 6) of the door/plenum 1 are lined with the acoustic foam 4 to prevent reflected noise from exiting exhaust openings 3 a on four sidewalls 3 b of the muffler door 1. The exhaust openings 3 c are positioned on the top, bottom, left and right surfaces of the acoustic door 1 on the sidewalls 3 b. When the door 1 is connected to a device 1 a at the opening 6 a, air from a cooling fan in the device 1 a enters the opening 6 a and exits through the sidewall exhaust openings (vents) 3 a.
The muffler door 1 has a depth 3 that creates a plenum chamber 2 sufficient as to not cause an impedance of airflow from the device 1 a. A notch 3 c in the bottom wall of the door 1 coincides with a pair of bridge lances located at the bottom rear of the device 1 a. The notch 3 c allows the door 1 to easily open and close around managed cables (attached to bridge lances using tie-wraps, cable ties, Velcro straps, etc.), providing power and communication to devices installed in the device 1 a.
FIG. 3 is another perspective view of an exterior of the muffler door 1, illustrating the endwall (or backwall) 6 and sidewalls 3 b of the door 1. The endwall 6 may be placed against a wall or other obstruction, thereby minimizing the floor space required in the office environment. Dividing security bars 7 in each side exhuast/vent 3 a are spaced so that modules such as I/O devices may not be removed through the openings 3 a.
Positioning the exhaust openings 3 a on the top, bottom, left and right surfaces of the acoustic door 1 on the sidewalls 3 b, allows air to freely exit the plenum chamber 2 (FIG. 2) to the outside environment, without a direct line of sight from the fans/blowers in the device 1 a to the outside environment to, as shown by the example side view in FIG. 4. Line of sight (LOS) is an indication of clear noise path and typically, the more LOS to the outside environment is obstructed, the greater reduction in exiting noise. Any one set of air exhaust openings 3 a may be obstructed without causing harm to the system.
FIG. 4 represents interior noise reflective surfaces (inside faces of the walls 3 b, 6) of the muffler door 1 covered with the acoustic absorbing foam 4. Position of exhaust openings 3 a at all sides/top/bottom exhaust, reduces the overall depth requirement of the muffler door 1, reducing its footprint. No ducting shell to turn all air exhaust at angles is needed, reducing depth requirements while achieving proper airflow. In the example implementation herein, using rectangular vents and acoustic foam sections, no angular or curved turning vanes are required, simplifying construction.
The parallel surfaces of the interior of the sidewalls 3 b of the manifold door 1 deflect/bounce noise sound waves back and forth to each other causing sound energy loss, converting the energy into heat, while the remaining amount of sound bounces back from the endwall 6, as shown in FIG. 4. The sidewalls 3 b are substantially parallel to each other, and substantially perpendicular to the endwall 6.
Stiffness/density of the walls 3 b, 6 of the door (enclosure) 1 are selected such that the resonant frequencies of the enclosure 1 are dampened and/or are moved outside the fan noise energy frequency range, preventing excitation of the fan noise frequencies. The walls can be made from metal, plastics, and other materials.
The acoustic foam 4 is selected in thickness, porosity and material type in damping fan noise. The fan energy lies in a finite frequency band. The foam porosity/air gap size is selected accordingly. Preferably, the foam 4 is selected such that the fan sound energy penetrates the foam 4, compressing the foam 4 at a microscopic level, such that as the energy penetrates deeper into the foam 4 the initial foam begins to recoil, pulling back on the foam 4 that is currently being compressed by the noise energy, thereby canceling some of the sound energy by converting it to heat. For example the foam 4 may be about one inch thick for the inside face of the sidewalls 3 b and about 1.5 inches thick on the inside face of the endwall 6. The foam may be cell polyurethane type M.
Depth 3 of the acoustical door 1 allows for more occurrence of the sound energy to impact the foam 4, wherein each time some noise energy is converted to heat, some noise is reflected back to an inside face of the parallel surface 3 b. From a thermal standpoint, the depth 3 is selected such that the fan exhaust air turbulence is reduced before it is directed out the side exhaust openings 3 a.
The manifold door 1 prevents increasing static pressure downstream of the air moving devices 1 a. In one example, the open area to airflow ratio is greater than or equal to 0.005 ft²/CFM in addition to a minimum depth of 0.5 ft, reducing airflow turbulence and velocity without increasing static pressure.
A combination of sides/top/bottom exhaust outlets 3 a accommodates inadvertent blockage of one side (e.g., if the side of the unit is placed against a wall). The door 1 can accommodate the airflow (and attenuate the noise) of various rack optimized computing units that fits in a rack (e.g., a 19′ wide rack). The acoustic muffler door may be hinged, making a latching door that easily allows access to rear cable connections modules in the device 1 a. In one example, the door 1 attenuates the acoustic levels of an installed system to general office acoustic sound levels of 6.5 Bels (or less), without impeding airflow in a way that causes overheating.
While certain exemplary embodiments have been described and shown in the accompanying drawings, it is to be understood that such embodiments are merely illustrative of and not restrictive on the broad invention, and that this invention not be limited to the specific constructions and arrangements shown and described, since various other modifications may occur to those ordinarily skilled in the art.

Claims

1. An acoustic cooling apparatus for a computing system, comprising:

a cooling muffler comprising sidewalls, a bottom wall and an endwall, the sidewalls being substantially parallel to each other, each sidewall being substantially perpendicular to the endwall at one end, the walls forming an enclosure having an open end opposing the endwall, the cooling muffler configured for attachment to a device having a rear air exhaust and to redirect airflow peripherally away from the rear of the device, the bottom wall including a notch and a plurality of bridge lances;

each sidewall including an exhaust opening; and

at least a portion of the interior of each wall of the enclosure being covered by sound absorbing material for attenuating air cooling sound.

2. The acoustic cooling apparatus of claim 1 wherein substantially the entire interior of each wall of the enclosure is covered by sound absorbing material selected based on the frequency of air cooling sound being attenuated.

3. The acoustic cooling apparatus of claim 1 wherein the sound absorbing material is selected in thickness, porosity and material type for attenuating cooling sound entering said open end, allowing the cooling sound energy to penetrate the sound absorbing material, compressing the sound absorbing material at a microscopic level.

4. The acoustic cooling apparatus of claim 3 wherein the sound absorbing material is selected to allow the cooling sound energy to penetrate into the sound absorbing material, causing recoil of the sound absorbing material and pulling back on the sound absorbing material being compressed by the sound energy, thereby canceling some of the sound energy by converting it to heat.

5. The acoustic cooling apparatus of claim 1 wherein each sidewall opening includes multiple dividing bars.

6. The acoustic cooling apparatus of claim 1 comprising four rectangular sidewalls and a square endwall, the sidewalls being substantially parallel to each other, each sidewall being substantially perpendicular to the endwall at one end and connected to side of the endwall square, the walls forming an enclosure having a square open end opposing the endwall.

7. A method of attenuating cooling sounds from a computing system, comprising:

providing an acoustic cooling apparatus comprising: a cooling muffler comprising sidewalls, a bottom wall and an endwall, the sidewalls being substantially parallel to each other, each sidewall being substantially perpendicular to the endwall at one end, the walls forming an enclosure having an open end opposing the endwall, each sidewall including an exhaust opening, at least a portion of the interior of each wall of the enclosure being covered by sound absorbing material for attenuating air cooling sound, the bottom wall including a notch and a plurality of bridge lances, the cooling muffler configured for attachment to a device having a rear air exhaust and to redirect airflow peripherally away from the rear of the device; and

connecting the open end of the acoustic cooling apparatus to a cooling device such that cooling air enters the open end and exits the exhaust openings, whereby the acoustic cooling apparatus substantially prevents line of sight between the sound generated by the cooling device and the outside environment.

8. The method of claim 7 wherein substantially the entire interior of each wall of the enclosure is covered by sound absorbing material selected based on the frequency of air cooling sound being attenuated.

9. The method of claim 7 wherein the sound absorbing material is selected in thickness, porosity and material type for attenuating cooling sound entering said open end, allowing the cooling sound energy to penetrate the sound absorbing material, compressing the sound absorbing material at a microscopic level.

10. The method of claim 9 wherein the sound absorbing material is selected to allow the cooling sound energy to penetrate into the sound absorbing material, causing recoil of the sound absorbing material and pulling back on the sound absorbing material being compressed by the sound energy, thereby canceling some of the sound energy by converting it to heat.

11. The method of claim 7 wherein each sidewall opening includes multiple dividing bars.

12. The method of claim 7 wherein the acoustic device comprises four rectangular sidewalls and a square endwall, the sidewalls being substantially parallel to each other, each sidewall being substantially perpendicular to the endwall at one end and connected to side of the endwall square, the walls forming an enclosure having a square open end opposing the endwall.

13. The acoustic cooling apparatus of claim 1, wherein the muffler device comprises a rear hinged door configured to latch onto the rear of the device having rear exhaust fans.

14. The acoustic cooling apparatus of claim 1, wherein the muffler device turns all air exhaust at angles needed without a ducting shell.

15. The acoustic cooling apparatus of claim 1, wherein depth of the muffler device reduces air turbulence before redirection out of the exhaust openings.

16. The method of claim 7, further comprising:

placing the muffler device directly against a wall, wherein floor space required for the cooling apparatus in an office environment is minimized.