WO2001061117A2

WO2001061117A2 - Sound reduction system and method

Info

Publication number: WO2001061117A2
Application number: PCT/IB2001/000192
Authority: WO
Inventors: James Wing Ho Wong
Original assignee: Acoustics Research Limite
Priority date: 2000-02-15
Filing date: 2001-02-14
Publication date: 2001-08-23
Also published as: GB2359569B; GB2359569A; GB0003519D0; WO2001061117A3; AU3399701A; GB0103745D0

Abstract

The invention involves sound reduction system and method especially for high density office, factory or apartment blocks, subject to exterior traffic and like noise. The absorbing members including cladding (F), sill extension panels (7) and/or sill fitted elongate sound absorbing member (E) are arranged around an openable window located in alcove above a non-opening window of the building.

Description

SOUND REDUCTION

The invention relates to a method of reducing sound to occupants of a room in a building. In the case of a multi-storey building in a busy urban area and in a hot environment the occupants of the room would like to open the windows for a breath of fresh air instead of relying on mechanical means. When they do so there is a tendency to be cooler, but unfortunately, they are subject to external noises. These can be the usual hustle and bustle of pedestrian activity or vehicular traffic. It is a gamble as to whether it is better to be hot and quiet or cool and subject to noise. It is an object of this invention to provide a means to address this problem, especially for multi-occupancy buildings which have little or no air conditioning.

According to the invention in one aspect there is provided a building having at least one level, the or each level of the building having at least one room exposed to the exterior of the building or noise source at lower level from the opening, each exterior wall including a closable vertical opening, noise reduction means being located adjacent thereto and shaped to reduce the level of incoming noise.

The noise reduction means is preferably shaped to present a barrier which may be in the form of an inclined surface. The free end of the means is shaped to reduce the sound intensity accumulating in the areas adjacent the opening.

In order that the invention may be well understood it will now be described with reference to the accompanying diagrammatic drawings, in which: Figure 1 is a vertical section of one embodiment of the invention,

Figure 2 is a vertical section of a second embodiment of the invention,

Figure 3 is a vertical section of a third embodiment of the invention,

Figures 4 and 5 are a plan view and a side view of a noise absorbing panel,

Figure 6 is a side view of a noise absorbing element fitted near an inset window, and

Figure 7 is a top view m section of noise absorbing cladding

The same reference numerals are used where convenient in describing the different embodiments

A multi-storey building has a number of floors F each made up of apartments comprising different rooms R At least some of the rooms have an outer wall 1 with a bay window 2 which projects forward of the outer wall A supplementary openable vertical window 3 is present in a recess or alcove 4 m the outer wall, above each bay window, the roof of the bay window defining a horizontal ledge 5 below and forward of the bay window The front face of the ledge 5 is covered by a noise absorbing element E This may be a metallic noise screen containing an acoustic absorbent membrane or filling material As shown in Figure 1 the element is secured to the free end of the ledge and projects slightly above and below and forward thereof The element may be secured in place using a mechanical means such as an interlocking channel parts or chemical means, e.g. an adhesive.

The element is about 700mm from the supplementary window 3. The leading edge of the element E absorbs sound transmitted from below and attenuates that from reaching the slab 6 above so preventing that slab from becoming a significant virtual noise source. When the window 3 is opened the level of sound in the room R is much reduced but cool air can enter and heat can escape from the room.

In the embodiment of Figure 2, the noise absorbing element E includes a panel 7 secured to the exterior wall 1 and projecting about 1200mm from the supplementary window.

The upper surface of the ledge is set at an angle to the vertical according to local requirements. If the angle is 75°, one can achieve a sound pressure level reduction of typical road traffic noise of about 1 1 decibels.

In the embodiment of Figure 3, the noise absorbing element F forms a 500 mm side barrier 8 formed part of the alcove window to the exterior wall. This arrangement reduces local reflections in the alcove and by including sound absorptive materials on the internal surfaces of the alcove, one can improve the sound pressure level reduction by a further 3 decibels.

In the embodiment of Figure 3, the sound absorbing means is a panel having perforations extending from the front face and the rear face. The perforations are shaped to absorb the sound. Extra sound absorbing material may be placed behind the panel.

As shown in Figures 4 and 5, the panel 7 could be trapezium shaped in plan view, i.e. with side edge 41 longer than side edge 42. However, the panel could have one of several shapes, for example, rectangular, or with the front edge curved or sinusoidal to form a succession of several waves. None of these alternative shapes are shown.

The actual shape is chosen by the designer or architect to give appropriate sound reducing characteristics but also to give a desired overall appearance of the building; it being appreciated that where the building is a high density apartment block or the like, there will be many windows with panels 7 in a regular pattern. Thus, the chosen panel shape will have a significant effect on the appearance of the building. The shape of the panels could vary from one window to another to give a desired overall appearance. For example, the front edges of the panels could be aligned along a shallow curve or the line of a series of waves or shallow triangular 'teeth' between the two sides of the building.

Each panel 7 may be curved or tilt downward slightly towards its front edge or to one or both sides to permit rainwater to flow away.

The panel 7 can be made of any suitable sound absorbing material, for example, wood, compressed wood fibre or cast fibrous material (e.g. cement mixed with wood or glass fibre filament bundles) and it could be fabricated from spaced upper and lower sheets of wood or compressed fibre board with a fibrous filling between. One or both of the upper and lower sheets could have regularly spaced perforations. The panel could be waterproofed, for example, as shown in Figure 5 by being wrapped in polyester film material. The outer edge 43 of the panel is fitted with a domed edge capping 44.

In Figures 4 and 5 the panel is fabricated from upper and lower sheets 45 of wood, fibre-board, plastics or metal, each sheet extending slightly backwards and forward from the extent of the sound absorbing infill 46. The forward extending portions 47 have inwardly extending flanges 48 to form a clip mounting for the domed edge capping 44.

The rearward extending portions 49 are engaged between, and fixed by, bolts 50 within the sides 51 of a channel section member 52. The channel section member 52 is fixed to the edge of the sill 5 by nuts 53 screwed onto threaded studs 54 which are cast into the sill 5.

As shown in Figure 6, the noise absorbing element E could comprise a tubular member 61 having a hexagonal cross-section. The member 61 could be made of sound absorbing material and it could be hollow or be filled with further sound absorbing material such as wood or glass fibre. The member 61 itself could be perforated or it could be made of perforated metal mesh.

The member 61 could be fixed direct to the sill 5 as shown in Figure 1 or it could be fixed to the front edge of a panel as shown in Figures 2, 3 and 6. As shown in Figure 3, the noise reduction measures comprise the noise absorbing element E and/ or the panel 7 and/ or the sound absorbing cladding F on the walls of the alcove. Depending on the amount of ambient noise and other requirements, the cladding F, panel 7 or element E could be used singly or in all different combinations. Figure 6 shows all three measures in use. The cladding F is mounted all round the alcove containing the window so that the sound is absorbed.

The sound absorbing cladding F could be as shown in Figure 7, i.e. it comprises spaced metal, plastic, wood or fibre-board sheets 71 with a sound absorbing filling 72 therebetween. Ideally, the cladding is spaced slightly from the exterior walls of the window alcove, for example, by being fixed to the relevant wall and/or roof of the alcove, by brackets 73, the brackets being fixed by expanding masonry bolts or anchor bolts 74.

The sound absorbing cladding F, panel 7 and noise absorbing element E could comprise members having holes therethrough which are specially shaped to improve the absorption of transmission therethrough of sound waves, i.e. so as to reduce reflection and secondary source generation. Thus, each hole could comprise a relative wide portion leading from one side of the member to a narrow opening which then widens out to the other side of the member, i.e. so that the hole is shaped somewhat like a handbell in cross-section. Further information on this disclosed in our International patent application No. dated

February 2001 to man Acoustics Limited or James Wong and Stephen Leung and claiming priority from UK patent application 0002641.9, the content of this UK application and the said International patent application being incorporated herein by reference.

Claims

1. A building having at least one level, the or each level of the building having at least one room exposed to the exterior of the building or noise source at lower level from the opening, each exterior wall including a closable vertical opening, noise reduction means being located adjacent thereto and shaped to reduce the level of incoming noise.

2. A building according to Claim 1, wherein the noise reduction means is shaped to present a barrier which may be in the form of an inclined surface.

3. A building according to Claim 1 or 2, wherein a free end of the noise reduction means is shaped to reduce the sound intensity accumulating in the areas adjacent the opening.

4. A building according to Claim 1 , 2 or 3, wherein the building is a high density apartment or office block with a substantially plurality of windows, each of the plurality of windows or at least openable ones thereof, having said noise reduction means located adjacent thereto.

5. A building according to Claim 1, 2, 3 or 4, including at least one room having a first window and, above that, a second window which is openable and mounted in an alcove, said noise reduction means being located in and around said alcove.

6. A method for reducing the transmission of sound from the outside to the interior of a building in a region adjacent a window of the building, the method comprising positioning sound absorbing members in said region around said window.

7. A method according to Claim 6, wherein said members including sound absorbing cladding fixed to the wall of the building around said window.

8. A method according to Claim 6 or 7, wherein said members include an elongate sound absorbing member fitted along the edge of a sill beneath said window.

9. A method according to any one of Claims 6 to 8, wherein the members include a sound absorbing panel fitted to the edge of the sill beneath said window and extending forward beyond said sill to shield traffic or other exterior noise from beneath the window.