lecture25 - Electronic reinforcement of sound 1 Sound...

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Electronic reinforcement of sound 1. Sound sources in a room Sound source can be characterized by power and directivity Directivity factor Q – ratio of sound intensity in front of the source to the averaged sound intensity Intensity drop as : 2 4 ) ( ) ( r wQ r A w r I π = = Intensity level : 2 4 log 10 ) ( r wQ L r L w + = For spherical source Q=1, for hemispherical Q=2, for source in a corner (which radiates into one- quarter of a sphere) Q=4
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2. Sound sources in a room The distribution of sound level in a room can be considered as a sound field Three regions in a sound field: Near field - distance from the source is small compared to dimensions of the source. Intensity varies with location and depends on the type of the source. Free field – intensity drops as 1/r 2 (r is distance from the source). Intensity level drops 6dB when distance r doubles Reverberant field – region where reflected sound becomes important r Near field Free field Reverberant field
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lecture25 - Electronic reinforcement of sound 1 Sound...

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