Noise measurement
First Claim
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1. A device for facilitating sound intensity measurements near a sound-reflecting surface, comprising:
- a pad of sound absorbent material having an overall shape which converges from a large basal area to a vertex thereby to provide a gradual change in acoustic impedance from said vertex of said pad to said sound-reflecting surface, at least the perimeter of said large basal area being intended to engage said sound-reflecting surface, andmeans for housing a microphone within a hole in said pad such that in use said microphone'"'"'s sound-sensing portion can be positioned substantially at said vertex.
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Abstract
A sound absorbent pad, which comprises an interconnected cellular foam or a fibrous material, has a central hole which houses a microphone whose sound-sensing diaphragm is held flush with the center of the outer surface of the pad. The pad is a shallow dome or other shape which converges from a large base to a vertex and incorporates a plastic or metal plate, which being frusto-conical or another suitable shape. The pad with its plate acts to control noise which would otherwise be reflected from noise reflecting surface onto the microphone, thereby facilitating measurement of freefield noise levels.
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Citations
15 Claims
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1. A device for facilitating sound intensity measurements near a sound-reflecting surface, comprising:
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a pad of sound absorbent material having an overall shape which converges from a large basal area to a vertex thereby to provide a gradual change in acoustic impedance from said vertex of said pad to said sound-reflecting surface, at least the perimeter of said large basal area being intended to engage said sound-reflecting surface, and means for housing a microphone within a hole in said pad such that in use said microphone'"'"'s sound-sensing portion can be positioned substantially at said vertex. - View Dependent Claims (2, 3, 4, 5, 6, 13, 14, 15)
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7. A device for facilitating sound intensity measurements near a sound-reflecting surface, comprising:
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a pad of sound absorbent material having an overall shape which converges from a large basal area to a vertex thereby to provide a gradual change in acoustic impedance from said vertex of said pad to said sound-reflecting surface, at least the perimeter of said large basal area being intended to engage said sound-reflecting surface, and means for housing a microphone within a hole in said pad such that in use said microphone'"'"'s sound-sensing portion can be positioned substantially at said vertex, the pad incorporating a plate having a shape which converges from a relatively large basal area to a narrower vertex area, said plate having a basal area and a base-to vertex dimension which are substantially smaller than the corresponding dimensions of said pad, said plate being positioned within said pad so that said vertex area is positioned underneath said sound-sensing portion of said microphone, thereby providing a sound-reflecting surface within said pad which is closer to said sound-sensing portion of said microphone than is said sound-reflecting surface beneath said device when said device is positioned thereon, whereby said plate acts to reduce the intensity of low frequency interference pattern at said microphone caused by reflection of low frequency and sound from said sound-reflecting surface beneath said device. - View Dependent Claims (8, 9, 10, 11, 12)
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Specification