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Howling often causes in a lecutre room, where a speaker uses a microphone and a loudspeaker.
Under the assumption that the speaker fixed on the cell or an upper side on a wall, we develope a howling canceller based on distance measurement. |  |
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Howling frequency depends on the distance between the microphone and the loudspeaker.
The relation between howling frequencies and the distance are shown the figure. When objects do not exist between the loudspeaker and the microphone, howling frequency strongly depends on the distance. |  |
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Distance measurement is achieved by using an ultra sonic sound.
The obtained distance is used to estimate howling frequencies. We implemented the proposed howling canceller onto a DSP. |  Experimental Result |