The roofs of sheds, conservatories and other outbuildings or extensions, and also attics and roof space rooms often consist of a single waterproof membrane, without effective sound insulation between the outer surface of the roof and the used space therebelow. Rainfall, particularly heavy or wind driven rainfall produces a considerable volume of noise due to the impact of water drops on the outer surface of the roof, and the larger and more numerous the drops, the louder and more intrusive the noise is.

The outer surface of the roof may be provided by metal sheeting, glass panels, polycarbonate panels, or wood panels. The first three in particular tend to effectively transmit sound and in some circumstances resonate. As a result frequent heavy rainfall with associated intrusive noise can lead householders to effectively abandon the use of extension space such as conservatories except during periods of settled rain-free weather.

GB-A-2374095 describes an arrangement for reducing rainfall noise on roof panels or windows comprising a mesh extended over and spaced from the roof panels. The mesh breaks up the raindrops before they impact upon the roof surface.

DE-A-19635463 discloses an installation for protecting skylights and roof windows from rain, particularly to minimize the noise of rainfall, which comprises a transparent rubber sheet which can be deployed by means of guide rails over the outer face of the window. The sheet is spaced from the window pane and has at least its outer face profiled in order to break up raindrops and thereby minimize the noise of impact. No details are given of

the geometry of the profiling and the arrangement is complicated, unsightly, and because of the space between the sheet and the pane, likely to attract condensation.

It is accordingly an object of the invention to provide a means for suppressing the noise of rainfall which is suitable for application to existing structures or for incorporation in new structures in order to lessen the disturbance and noise caused by in particular heavy rain and which does not rely upon fully sound insulating material without the need for provision of structures for deployment or spacing and eliminating the drawbacks of such structures.

In accordance with the invention, means for suppressing the noise of rainfall comprises means providing an exposed outer surface for a roof or the like characterised in that said surface is formed with projections which serve to break up raindrops to spread their impact upon the surface and that the means comprises a sheet directly adhered to a roof panel or window pane.

The projections may comprise parallel ribs formed on the exposed outer surface or an array of discrete peaks in the form of e. g. domes, cones or pyramids. Alternating ribs or peaks may be respectively higher than the ribs or peaks in between the higher ribs or peaks.

The said surface may be provided on a sheet of flexible material which may be part of a roofing membrane or material, or may be a cladding or overlay for mounting on the outer surface of a preexisting or new roofing membrane or material.

The sheet of flexible material may be transparent or translucent or opaque, depending upon the required light transmitting characteristics of the roof upon which it is mounted or forms part. Conservatory roof panels will

usually be fully transparent but for other uses, the sheet may pass diffused light, or be fully opaque.

The sheet of flexible material may incorporate or be coated with a colour change material, such as photochromic material, that is one which changes colour on exposure to incident radiation of a particular waveband or "colour". The photochromic material may be incorporated by being mixed with the material forming the sheet, or be a layer sandwiched between two laminated layers forming the sheet, or be a coating provided on the inner or outer surface of the sheet.

The photochromic material is preferably selected to darken or gain intensity when exposed to ultra-violet radiation, as in strong sunlight, and may comprise an ink, pigment or dye having the required photochromic response. The colour change may be selected to be from clear or translucent to for example orange-yellow, blue, or neutral density (grey).

Alternate possible materials pigments, which change colour or darken include thermochromic materials, which are triggered by an increase in temperature, and electrochromic materials which are triggered by application of a voltage to change their chemical state and hence colour.

The material is also preferably UV and weather resistant, and should conform to relevant standards and building regulations.

The invention will now be further described with reference to embodiments thereof given by way of example, and as shown in the accompanying drawings, wherein:- Fig. 1 is a cross-sectional view of a first embodiment of rainfall noise suppressing means as applied to a conservatory roof window panel.

Fig. 2 is a cross-sectional view of a second embodiment of rainfall noise suppressing means according to the invention;

Fig. 3 is a perspective view of the outer surface of the embodiment of Fig. 1 ; Fig. 4 is a perspective view of the outer surface of the embodiment of Fig. 2; Fig. 5 is a diagram illustrating a possible (non limiting) theory as to how the noise reduction is achieved, and Fig. 6 is a sectional view of a further embodiment of the invention.

A first embodiment of rainfall noise suppressing means according to the invention, as applied to a transparent window pane of a conservatory roof, is shown in a fragmentary cross-sectional view in Fig. 1. A transparent polycarbonate glazing panel or pane 10 has its peripheral edge retained in a glazing bar 11, and a sheet 12 of a transparent plastics material which covers the upper (outer) surface of the glazing panel 10, and may be attached to the surface of the glazing panel 10 by a suitable adhesive or by an array of suction caps in the form of shallow recesses in the underside of the sheet 12. The exposed outer surface 14 of the sheet 11 is formed with a myriad of protrusions 16, in the form of domes, of two alternating sizes 16a and 1 6b. The larger domes 16a are higher and of greater diameter than the smaller domes 16b which alternate in diagonal alignment with the domes 16a. The larger domes 16a are about 5mm in height and diameter, whilst the smaller domes 16b are about 3mm in height and diameter.

The geometry of the protrusions 16 may be varied, for example, they could be conical, square or polygonal pyramids or the like, and may be arrayed randomly rather than in rows.

Fig. 2 shows in a fragmentary cross-section a translucent or transparent polycarbonate glazing panel or panel 20 for a conservatory or other roof, having a second embodiment of sheet 22 of a transparent or

translucent plastics material which covers the upper (outer) surface of the glazing panel 20. The exposed surface (21) of the sheet 22 is in contrast to the sheet 12 of Fig. 1, formed with an array of parallel ridges or fins 24, disposed as alternating high ridges 24a and low ridges 24b. The crests of the high ridges 24a are typically about 5mm apart, with the lower ridges 24b spaced midway between them. The high ridges 24a may be about 5mm high from trough to ridge, whilst the lower ridges 24b are about 3mm high from trough to crest.

These dimensions are not intended to be limiting, and are included solely as an indication of the scale and order of size of the protrusions or ribs provided on the sheets 11 or 20.

Figs. 3 and 4 are respective perspective views showing the exposed surfaces of the sheets 11 and 20 respectively.

Fig. 5 is included as an illustration of a theory as to why the surface configuration of the sheets 11,20 and other similar configurations are effective in reducing the noise of rainfall. As shown on the left of the figure, a raindrop 50 falling on a planar surface impacts the surface substantially simultaneously, with its surface tension boundary intact until the moment of impact, and the drop collapses as at 51 generating sound waves in the material impacted upon.

With the surface configuration provided by the sheets 11, 20 a raindrop 52 will contact a protrusion 53 at one point before the drop 52 falls to the surface, disrupting the surface tension boundary of the drop, and allowing the water to flow out of the drop before its full mass completes the descent, as at the right in Fig. 5. This has the effect of spreading the arrival of the drop onto the surface over time (a fraction of a second as opposed to

virtually instantaneously) reducing the volume of noise produced, as the noise is spread over a longer period of time.

Fig. 6 is a modified embodiment of the invention including an upper or outer layer 61, having a surface contoured in accordance with the invention to achieve substantial noise reduction, and a lower supporting layer 62.

Sandwiched between the layer 61 and 62 is a layer 63 of a photochromic material which is adapted to change colour or darken on exposure to UV radiation. Alternatives include thermochromic materials which change colour with temperature change and electrochromic materials which change colour on application of a voltage. The layer 63 is protected from weathering by the outer layer 61, and helps to reduce the intensity of strong sunlight due to reducing transmission of light. The layer 63 may comprise a gel or other medium incorporating a photochromic, thermochromic or electrochromic pigment, ink or dye which is adopted to for example turn to an orange- yellow, blue or neutral density (grey) shade from translucence as a result of absorbing UV radiation.

Alternatively the photochromic, thermochromic or electrochromic material would be dispersed in the upper or lower layer 61 or 62, or coated on the outer or inner surface of the composite sheet.

The separation of the protrusions is in the same order of size as the diameter of raindrops from a heavy shower; thunderstorm drops are somewhat larger. Light rain and drizzle produces smaller drops or droplets, but these generate little noise during precipitation. Noise level increases with drop size and terminal velocity, particularly when accelerated by wind or downdraught. The separation of the protrusions ensures that part of all of these larger raindrops will strike a protrusion before impacting the surface

thereby dissipating the kinetic energy of the arrival and associated noise emission over a longer period of arrival than the usual instantaneous impact.

The material of the sheets 12 and 22 is preferably a flexible polyurethane which is UV-resistant to relevant standards, so as to maintain the required transparency or translucence to match that of the glass or polycarbonate panes to which it is laminated. The sheets 12,22 can for example be fabricated by casting on a roller which has its surface suitably contoured e. g. by engraving to provide the requisite domes or ridges or other protrusions.

In a new installation, the glazing panels or other roof panels may be supplied ready laminated with material such as sheets 12 or 22, providing a unit comprising a rigid main body, and an overlying layer laminated or otherwise formed thereto providing the surface with protrusions.

The noise, suppression means according to the invention enables the noise level in extensions such as conservatories during heavy rainfall to be reduced significantly with respect to the noise level experienced without provision of a noise reducing means as described hereinbefore. In consequence, it is possible to make more use of spaces such as conservatories as additional living space as normal conversation and entertainment can be carried out without rain noise rendering conversation or the like inaudible, and the psychological effects of discomfort experienced when hearing heavy rainfall.

The utility of conservatories, and therefore their value to the owner is considerably increased by use of the invention.

It is of course to be understood that the invention is not intended to be restricted to the details of the above embodiments which are described by way of example only.