Microphone Array and Beamforming - Forward麦克风阵列波束形成了.pptVIP

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Microphone Array and Beamforming - Forward麦克风阵列波束形成了.ppt

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Microphone Array and Beamforming - Forward麦克风阵列波束形成了

Microphone Array and Beamforming By Pattarapong Rojanasthien ECE 5525 Dr. Kepuska December 8th, 2008 Overview Introduction Background Microphone Arrays Beamforming Signal to Noise Ratio Solution and Approach Results Conclusion Introduction The goals for the project are the following Learn the basic concept of microphone array Become familiar and learn how to use a program that perform Beamforming Show that Beamforming will enhance the signal quality based on SNR Microphone Array Multiple microphones set up in certain formation depend on the application. Line Circle Rectangle Each microphone will capture the sound from the source at the different time due to distance from the source. Therefore, there is a time delay in each signal. Microphone Array Multi-Channel Signal Comparison Time Delay Note that the distance between another microphone (not the reference) to the source, which denote as g, can be compute with trigonometry cos ? = d/g = d = g cos?. The distance from source to Ref Mic: d = 30 in. The distance from source to Mic x: g = 34.73 in. The distance between mic: N = 17.5 in. Sampling Frequency: fs = 22050 samples/sec. Speed of sound: c = 345 m/sec. Find d’ = 34.73 – 30 = 4.73. Find Sample/meter = 22050/345 = 63.913 samples/m. Turn into inches = 63.913 x 0.0254 = 1.62 To find time delay, we need distance d’ x = 4.73 x 1.62 = 7.7 samples, round up to be 8 samples. Example of Microphone Array Beamforming A technique that rearrange the mixture signals from the microphone array, so that the signals from the source that we want are lined up before combine them all up into one signal Since signals from the specified source are on the same phase, they will add each other up. The noise signals may either add each other up or cancel each other out. The general form of the beamforming output based on delay and sum Beamforming Pattern Signal to Noise Ratio The measurement of the signal quality Basically, it is the magnitude of One way to calculate it is to find no