GB2451795A

GB2451795A - Soundproofing IT hardware and electronic equipment enclosures

Info

Publication number: GB2451795A
Application number: GB0715762A
Authority: GB
Inventors: Jeremy Sinclair Goodman
Original assignee: ACOUSTI PRODUCTS Ltd
Current assignee: ACOUSTI PRODUCTS Ltd
Priority date: 2007-08-13
Filing date: 2007-08-13
Publication date: 2009-02-18
Anticipated expiration: 2027-08-13
Also published as: GB0715762D0; GB2451795B

Abstract

A layered material for soundproofing material for IT hardware or other electronic equipment enclosures comprises (1) an acoustic foam layer 120, (2) an acoustic barrier layer 115 and (3) a self-adhesive layer 105, the foam layer being physically bonded (i.e. mechanically bonded without adhesive) to the barrier layer and the self-adhesive layer being attached to a face of one of the barrier layer and the foam layer, the overall thickness of the layered material being no more than 12.7mm. A second foam layer may be physically bonded to the barrier layer such that the barrier layer is between foam layers. The foam layer(s) may be dense open celled polyurethane foam. The acoustic barrier layer may be made from polyvinylchloride-based mass-loaded plastisol.

Description

MATERIALS FOR SOUNDPROOflNG IT HARDWARE AND ELECTRONIC

EOUIPMENT

The present invention relates to materials for soundproofing information technology hardware and electronic equipment. It finds particular application in kits of parts for soundproofing enclosures such as rackmount cabinets.

Excessive acoustic noise (that is, unwanted airborne Sound) levels are a growing problem in information technology (IT) hardware. Many different sources such as international environmental noise standards, white papers, websites, and novel inventions designed to reduce IT hardware noise are evidence of this trend and problem. IT hardware is deployed into many different indoor environments where it is situated in close proximity to humans. Environments include domestic rooms, offices, schools, hospitals, and dedicated computer rooms. I5

Where IT hardware is close to humans, it is advantageous for it to be quiet or near-silent. Studies show that reduced noise levels from IT hardware result in improved cognitive function and improved concentration ability. Quiet IT hardware therefore increases productivity and efficiency in the workplace, improves the productivity in educational environments, and restores a natural low noise pollution environment in hospitals and homes.

There are multiple sources of noise-generating components inside IT hardware. Computers, servers, networking, communications and other IT equipment, most commonly have built-in fans designed to air-cool warm electronic and mechanical components. It is most common that air moving fans are the single largest noise-generating source of broadband noise (that is noise across the audible frequency spectrum (100Hz to 20kHz)). Other components incorporating mechanical mechanisms, such as hard disc drives (HDD), generate mechanical noise, and noise from vibration of parts. Electrical and electronic circuitry, such as transforming coils and printed circuit boards also generate noise.

To reduce noise from IT hardware, sound-absorbing materials such as acoustical foams have been manufactured for deployment into enclosures that surround or encase IT equipment.

Acoustic materials have been used in a wide range of enclosure sizes, from small cases surrounding a typical desktop personal computer (PC) up to larger volume enclosures, such as those used to house 19-in rack mounted server and communication equipment.

There are several factors in the suitability of soundproofing materials for IT hardware, these being: * acoustic effectiveness at relevant frequencies * low flammability * lifetime, in particular not delaminating over time * dust free, or non-shedding Acoustic materials are known which are intended for use in lining the inside of computer enclosures to help reduce unwanted sound. The materials almost all employ a foamed material facing the noise source and often come in packs containing several sheets, either cut to fit a particular housing or for cutting to size by the user. Some packs use a two-layer material where a foam is laminated to a thinner dense heavy layer, often called an acoustic barrier layer. All packs have a self-adhesive base layer for easy application to the substrate.

Known examples of various types of material include the following: * a single layer of Black Nitrile Rubber closed cell foam * two layers, being acoustic foam and an acoustic barrier * two layers, being white Melamine foam and an acoustic barrier * three layers, with two foam layers and an intervening vinyl acoustic barrier * a single, fibre-based layer Over recent years the physical space (that is, volume) occupied by IT hardware has reduced due to improvements in manufacturing technologies that facilitate smaller components. Lower volume hardware is economically advantageous, as it offers a user a more efficient use of valuable room space. For example, Internet service providers (ISPs) hosting multiple servers in a controlled server room environment can add extra revenue-generating equipment for the same physical space if new or replacement equipment is miniaturised.

Acoustic materials used inside IT hardware require physical space. Thinner materials that exhibit the same or even higher acoustical performance are advantageous, and overcome volume usage problems caused by bulky materials.

Lighter weight per unit area acoustic materials represent savings in shipping costs before and after installation into iT hardware. Some IT hardware is portable, and reduction in weight of acoustic materials installed in such hardware is an advantage. IT hardware is commonly installed in a single location, and dense equipment can reach or exceed floor loading capacities in buildings, therefore restricting the amount of equipment installed in a given room space. Any weight reduction of IT hardware is an advantage, thus lighter acoustic materials installed inside IT hardware enclosures are an advantage.

Should shaped parts of acoustic materials be manufactured, they eliminate the labour time required for cutting to shape, and therefore speed up installation both into single enclosures or multiple installations, such as would occur on a factory production line.

According to a first aspect of embodiments of the present invention, there is provided a layered material for use in soundproofing IT hardware and/or electronic equipment enclosures, the material comprising: i) an acoustic foam layer; ii) an acoustic barrier layer; and iii) a self-adhesive layer the foam layer being physically bonded to the barrier layer, the self-adhesive layer being attached to a face of one of the barrier layer and the foam layer and the thickness of the layered material being not more than 12.7 mm.

Embodiments of the invention in its first aspect can provide a composite soundproofing material of no more than Y2" thickness. Embodiments of the present invention show very acceptable acoustic performance while being significantly thinner than known soundproofing constructions for IT enclosures.

"Physically bonded" in this context is intended to mean a mechanical locking of layers with no adhesive being used. In practice, the barrier layer may for example be applied to a foam layer in semi-liquid form which will sink into the foam layer so that the barrier layer in the finished layered material incorporates material of the foam layer.

Either one or two layers of foam material can be used. Superior acoustic performance is achievable where a second foam layer is physically bonded to the barrier layer so that the barrier layer is sandwiched between foam layers. Such a construction can be made with a thickness of less than 12.7 mm (1/2 inch), indeed as thin as 7 mm, and still show very good soundproofing properties for IT or other electronic equipment enclosures. However, for some applications, this is still too thick and a construction using just one layer of foam material bonded to the barrier layer can be made as thin as 3.8 mm and yet still show good soundproofing properties.

According to a second aspect of embodiments of the present invention, there is provided a kit of parts for soundproofing an IT enclosure, the kit of parts comprising a plurality of sections of layered material according to the invention in its first aspect, which sections are shaped and sized so as to fit together to line the IT enclosure.

A kit of parts for soundproofing an IT enclosure will now be described as an embodiment of the present invention, by way of example only, with reference to the accompanying figures in which: Figure 1 shows a vertical cross section of material from which the kit of parts is constructed, adhesively attached to a substrate; Figure 2 shows a vertical cross section of material which has one fewer layers than the material of Figure 1; Figure 3 shows a graph comparing the acoustic performance of a three layer material with a two layer material, both according to embodiments of the present invention; Figure 4 shows a graph comparing the acoustic performance of a two layer material with a one layer material, only the first material of the two being according to an embodiment of the present invention; Figures 5 and 6 show side and front elevations of an IT enclosure the kit of parts might be used to soundproof; and Figure 7 shows in plan view the kit of parts prior to use in the IT enclosure of Figures 5 and 6.

1. LAYERED MATERIAL Referring to Figure 1, a layered material from which the kit of parts might be constructed is attached to a substrate 100 by an adhesive layer 105. The adhesive layer 105 is attached to a first foam layer 110 of the material and an acoustic barrier layer 115 is sandwiched between that first foam layer 110 and a second foam layer 120. The total depth of the layered material as shown in Figure 1 is 12.7 mm but a version can be made with a depth as little as 6.9 mm.

Referring to Figure 2, in a version of the material which can be made with less depth than that shown in Figure 1 but which still gives very good acoustic performance, only the second foam layer 120 is present, the barrier layer 115 being adhered to the substrate rather than sandwiched.

The total depth of the layered material in this case is 3.8 mm.

Layer thicknesses are further discussed below.

In Figures 1 and 2, the pores 125 of the foam layers 110, 120 are only partially shown for the purpose of clarity.

The nature of the various layers is as follows.

1.1 Adhesive layer 105 The adhesive layer 105 is provided as a double coated polyester film supported tape. A high-tack, moderate dead load acrylic adhesive film is coated on both sides of a high quality polyester film. It is backed (on the substrate side) by a standard silicone treated densified Kraft' paper release liner, that is removable by peeling prior to installation.

The adhesive layer 105 provides a low flammability self-adhesive membrane for easy application to a wide range of surfaces, including those commonly found inside IT hardware IS enclosures, namely: o sheet metal, o powder-coated metal, o painted metal, o plastics, o untreated wood (including MDF and fibreboard), o wood laminates with and without paint and varnishes o glass 1.2 First and second foam layers 110, 120 The first and second foam layers 110, 120 are each a dense open-cell polyurethane foam, typically 64kg/rn3, with a tensile strength of I4OkPa, elongation of 218% and tear resistance of 400N/m. The visual cell count is 20(+f-3) pores per cm. The foam composition contains a proprietary flame retardant consisting of one of more components, giving a low flammability characteristic as per UL94 of}{F-1 at 3.18mm minimum thickness.

These materials are of course examples only. It would be possible to use substitute materials with similar properties, or a polyurethane foam with somewhat different properties, for example a higher visual cell Count. It is also not essential that both foam layers 110, 120 are the same. It may be found appropriate for instance to use foam layers 110, 120 with different densities and thicknesses.

1.3 Acoustic barrier layer 115 The acoustic barrier layer 115 is a polymeric material and, in particular, a continuous layer made from polyvinylchloride-based (PVC-based) mass-loaded plastisol; that is, a suspension of PVC and plasticizer. The proportions and types of compounding ingredients can be varied to give different densities as well as different thicknesses. It is an important constituent of the layered composite material as the raw material cost is relatively high and the material itself is dense relative to the other layers, affecting overall weight in use and transport and so on of the layered composite material.

In embodiments of the invention, a foam layer 120 will face the noise source rather than the barrier layer 115, so where there is only one foam layer 120 it is the barrier layer 115 which will be adhered to the substrate 100.

1.4 Layer thicknesses The thicknesses of the various layers used can be varied and this will of course have an impact on various aspects of acoustic performance, utility and cost.

In a three layer version, the thicknesses can be varied as follows while still providing an acceptable level of sound proofing without taking up too much space in a computer or IT hardware cabinet: * overall thickness -from 6.9mm (0.27 in), up to a maximum of 12.7mm (0.5 in) * first and second foam layers 110, 120-from 3.2 mm up to a maximum of 9.6 mm * acoustic barrier layer 115 -from 1.0 mm up to a maximum of 2.0 mm as applied, reducing to a thickness as little as 0.4 mm or 0.5 mm up to perhaps 1 mm in the finished material * adhesive layer 105 -including the release liner, this is typically 5.6 to 7.6 thousandths of an inch, equivalent to 0.14 to 0.19 mm The barrier layer 115 is applied in a semi-liquid form in a method further discussed below. It sinks into the foam and thus although it may have an approximate 1mm to 2mm thickness during manufacture, when bonded to the foam it has close to zero thickness. The overall thicknesses of the layered composite materials given herein are the finished product thicknesses (unless the context indicates otherwise), and not the sum of the component thicknesses which would be higher.

There is of course no inherent physical upper limit to the thickness of the layers except for the limitations of methods of manufacture, although in practice there are economic reasons for keeping the layers relatively thin, for instance no more than 7mm, as well as the question of space in the IT hardware enclosures.

In a two layer version, comprising principally an acoustic barrier layer 115 and a foam layer 120, the thicknesses of the individual layers will be as for the three layer version and the overall thickness might typically be in the range from 3.75 mm up to 4.25 mm 1.5 Additional layers There is no reason layers in addition to those described above cannot be used, provided they do not detract from the performance of the layered material in use, for example increasing flammability or giving the material unwanted electrical characteristics. An additional layer might be for example a thin foam facing' layer on the exposed face of the second foam layer 120. This additional layer on the foam is typically added to provide some increased measure of flame retardancy, and/or abrasion resistance, and/or protection against the ingress of dust, water and/or oils. Thin facing materials for this purpose may include, but are not limited to, polyurethane and PVC.

2. ACOUSTIC PERFORMANCE Referring to Figures 3 and 4, comparisons of acoustic performance can be made using the known test method ASTM C384-98 "Standard Test Method for Impedance and Absorption of Acoustical Materials by the Impedance Tube Method".

Figure 3 shows two curves 300, 305, these being: dashed curve 300 -three layer material 6.9 mm overall thickness, the two foam layers each being approximately 3.2 mm thick. This material includes a thin but dense barrier layer 115, being applied at 1 mm thickness but reducing to 0.5 mm in the finished material. The barrier layer 115 has a weight per unit area of 3.66 kg/rn2 and a density of 3,660 kg/rn3.

solid curve 305 -two layer material 7 mm overall thickness, this material includes a foam layer 120 of 5.5 mm thickness and a thicker but less dense barrier layer 115 of 1.5 mm thickness in the finished material. The barrier layer 115 in this case has a weight per unit area of 3.72 kg/rn2 and a density of 2,488 kg/rn3.

It might be noted that the thickness of each layer is likeiy to vary in practice by up to plus or minus 10% and the thicknesses given are the average thicknesses.

S These examples show a range in density appropriate to the barrier layer 115 of approximately 2,400 kglm3 to 3,700 kg/m3.

Both curves are showing acoustic performance over the mid to low frequency spectrum, that is up to 2 kHz. At frequencies above this, across the audible spectrum to 20 kHz, acoustic performance of both types of material is fully acceptable, and indeed the acoustic performance of many foam materials having an overall thickness of 3.2 mm and above. However, it can be seen that in the mid to low frequency range the three layer material gives a significantly enhanced performance in spite of its thinner acoustic barrier layer 115. That is, it shows a sound absorption coefficient of at least substantially 0.06 over the frequency range 400 to 2000 Hz.

This use of thinner barrier layers 115 allows the manufacturer to keep costs down and reduce the weight of the layered materials per unit area.

In general, it seems from test data that thickening and/or making more dense the central barrier layer 115 gives increased performance in the lower frequency range around and below 1,000Hz.

Further, the use of a three layer material gives significantly improved performance in this frequency range over a two layer version. Because of its enhanced performance, the three layer construction offers improved acoustic performance, lighter weight and thinner materials, with lower raw material costs.

Figure 4 shows two curves 400, 405, these being: dot-dashed curve 400 -two layer material 3.8 mm overall thickness with just one foam layer 110 approximately 3.2 mm thick and the thin but dense barrier layer 115 mentioned above, being applied at about 1 mm thickness but reducing in this case to 0.6 mm in the finished material. Again the barrier layer 115 has a weight per unit area of 3.66 kg/rn2 and a density of 3,660 kg/rn3.

solid curve 405 -single layer material A single layer of foam of 4 mm overall thickness with a self-adhesive layer 105 but no barrier layer.

In the above there is an apparent inconsistency in that the barrier layers 115 for the materials of curves 300 and 400, shown dashed and dot dashed respectively in Figures 3 and 4, have the same weight and density but different thicknesses in the finished material. This is a consequence of the manufacturing method in which the barrier layer 115 is applied wet to the foam layers 110, 120 and sinks in to a certain extent. The thicknesses of the barrier layers 115 quoted in relation to Figures 3 and 4 are the thicknesses of that part of the barrier layers 115 which lies between or proud of the foam layers 110, 120 and thus contributes to the overall thickness of the material. In a two layer material, the barrier layer 115 is only applied to one foam layer 120 instead of two and thus sinks in to a lesser extent.

The curves 400, 405 of Figure 4 show a clearly improved acoustic performance of the material having an acoustic barrier layer 115 even at these low overall thicknesses. For example, the curve 400 for the material having an acoustic barrier layer 115 shows a sound absorption coefficient of at least 0.04 over the frequency range 400 to 600 Hz.

3. METHOD OF MAKING Both two layer and three layer materials are physically bonded (rather than laminated using compositing adhesives) using a single in-line manufacturing process.

The manufacturing process is two-fold: (i) foam is physically bonded to the upper side (and underside in the three layer version) of the acoustic barrier layer 115 to give the foam layers 110, 120, and (ii) self adhesive tape 105 is applied physically to the composite The vinyl barrier is applied as a viscous liquid, and is coated by a knife-over-roll process onto the lower foam layer 110 to a measured thickness, usually in the range from 1 mm to 4 mm. The upper foam layer 120 is then added in-line to the upper surface of the barrier layer 115, and the three layers physically bonded by pressure applied by a weighted roller.

The composite material is then oven heated to the fusion temperature of the plastisol, where the PVC absorbs the plasticiser and fuses into a plasticized PVC Continuous layer, bonding the two foam layers 110, 120 together and to the intermediate barrier layer 115. The fusion process is not reversible, making the finished bond permanent.

Double-sided self-adhesive tape is applied by pressure roller to the finished composite to provide the adhesive layer 105.

Shaped parts can then be die-cut. This is achieved by vertical or near-vertical die pressing of the materials using a shaped blade to produce filly cut and partially cut parts to defined desired dimensions.

4. KIT OF PARTS Referring to Figures 5 to 7, embodiments of the present invention include a kit of thin acoustic material parts (less than 12.7 mm or 0.5 in) with improved acoustic performance intended to be applied to the inside surfaces of an enclosure for example IT hardware and electronic equipment. Such an enclosure might be for example any one of: -a desktop, tower or pedestal case (or chassis) for application as a home or office personal computer (PC) -a desktop, tower or pedestal case (or chassis) for application as a server -PCs and servers including the following common case (or chassis) form factors: SFF (Small Form Factor), ATX, and BTX -a rackmount equipment case (or chassis), including rackmount server and communication equipment cases -a rackmount cabinet (sometimes called a l9inch rack' enclosure) It might be noted that 19 inch rack enclosures in particular are in wide usage for many types of equipment that might benefit from embodiments of the present invention, such as broadcast and audio visual equipment.

Figure 5 shows a side elevation of a rackmount equipment cabinet 500 and Figure 6 shows a front elevation thereof. The side elevation of Figure 5 also shows installed 19" rackmount equipment 505.

Layered composite material according to embodiments of the present invention can be supplied as a kit of parts, either being cut to predefined shapes for installation, which is considerably easier for the installer and reduces installation time, or being supplied as sheets for cutting by the installer.

Figure 7 shows a kit of parts 700, 705, 710 for installing in the rackmount equipment case 500.

This kit of parts is produced by a known die-cutting process which can produce even quite intricate shapes and a range of dimensions from 20x20 mm up to 1.3 x 4.0 metres. It also deals with different thicknesses such as the kit of parts shown in Figure 7. These include pieces of different thicknesses for lining different areas of the equipment case 500 such as a first piece 700 of medium thickness at 10.3 mm, a second piece 705 of greater thickness at 12.0 mm and a third piece 710 of least thickness at 6.9 mm. These pieces can each be perforated-cut along various fold lines to aid installation.

5. ADDITIONAL ADVANTAGES Advantages available with embodiments of the present invention not already mentioned above are: -non-shedding formulation, using foamed acoustic materials that incorporate flame retardants in the foam matrix composition rather than post-treated foams or fibre-based materials (lower dust and loose fibre generation) -when supplied in sheet form (not as shaped parts) the materials are flexible and easy to cut and shape by hand with standard utilities such as a craft knife or scissors.

-low flammability (3.8 mm up to 6.9 mm = UL94-V0, and from 7.0 up to 12.7 mm UL94-V2)

Claims

CLAiMS 1. A layered material for use in soundproofing IT and/or electronic equipment enclosures, the material comprising: i) an acoustic foam layer; ii) an acoustic barrier layer; and iii) a self-adhesive layer the foam layer being physically bonded to the barrier layer, the self-adhesive layer being attached to a face of one of the barrier layer and the foam layer and the thickness of the layered material being not more than 12.7 mm.
2. A layered material according to Claim 1, having an overall thickness of not more than 4.25 mm.
3. A layered material according to Claim I further comprising a second foam layer physically bonded to the barrier layer such that the barrier layer is between foam layers.
4. A layered material according to Claim 3 having an overall thickness of no more than 7 mm.
5. A layered material according to any one of the preceding claims wherein at least one foam layer comprises a polyurethane foam.
6. A layered material according to Claim 5 wherein the polyurethane foam has a visual cell count in the range seventeen to twenty three pores per centimetre inclusive.
7. A layered material according to any one of the preceding claims wherein the acoustic barrier layer comprises a polymeric material.
8. A layered material according to Claim 7 wherein the barrier layer comprises a mass-loaded plasticized PVC continuous layer.
9. A layered material according to any one of the preceding claims wherein the acoustic barrier layer has a density in the range from 2,400 kg/m3 to 3,700 kg/m3.
10. A layered material according to any one of the preceding claims wherein the average thickness of the or each foam layer lies in the range from 3.2 mm up to 9.6 mm inclusive.
11. A layered material according to any one of the preceding claims wherein the thickness contributed by the acoustic barrier layer lies in the range from 0.4 mm up to 1 mm inclusive.
12. A layered material according to any of Claims 4 to 11, having a sound absorption coefficient of at least substantially 0.06 over the frequency range 400 to 2000 Hz.
13. A layered material according to any one of the preceding claims, having an overall thickness of not more than 4.25 mm and a sound absorption coefficient of at least 0.04 over the frequency range 400 to 600 Hz.
14. A kit of parts for soundproofing an IT and/or electronic equipment enclosures, the kit of parts comprising a plurality of sections of layered material according to any one of the preceding claims.
15. A kit of parts according to Claim 14 where the sections are shaped and sized so as to fit together to line the IT and/or electronic equipment enclosures.