Patent ID: 6505057
Filing Date: 2003-01-07
Classification: G10L

Abstract:
An integrated vehicle voice enhancement system and hands-free cellular telephone system comprising:a near-end acoustic zone; a far-end acoustic zone; a near-end microphone that sense sound in the near-end zone and generates a near-end voice signal; a far-end microphone that sense sound in the far-end zone and generates a far-end voice signal; a near-end loudspeaker that inputs a near-end input signal and outputs sound into the near-end zone; a far-end loudspeaker that inputs a far-end input signal and outputs sound into the far-end zone; a near-end adaptive acoustic echo canceler that receives the near-end input signal and generates a near-end echo cancellation signal; a near-end echo cancellation summer that inputs the near-end voice signal and the near-end echo cancellation signal and outputs an echo-cancelled, near-end voice signal; a far-end adaptive acoustic echo canceler that receives the far-end input signal and generates a far-end echo cancellation signal; a far-end echo cancellation summer that inputs the far-end voice signal and the far-end echo cancellation signal and outputs an echo-cancelled, far-end voice signal; a microphone steering switch that inputs the echo-cancelled, near-end voice signal and the echo-cancelled, far-end voice signal and outputs a telephone input signal; and a cellular telephone that inputs the telephone input signal; wherein at least one noise reduction filter is used to improve the clarity of the telephone input signal inputting the cellular telephone; wherein the noise reduction filter is a recursive implementation of a discrete cosine transform modified to stabilize its performance in a digital signal processor, each of the plurality of fixed filters is a finite impulse response filter, and the finite impulse response filters are represented by the following expression: zm&af;(k)=&Sum;n=om-1&it;[GmM&it;Î³N&it;cos&it;â€ƒ&it;(Ï€&it;â€ƒ&it;(2&it;n+1)&it;â€ƒ&it;m2&it;M)]Ã—(k-n)where M is the number of fixed filters, x(k-n) is a time-shifted version of the raw input signal, n=0,1 . . . M-1, zm(k) is the filtered input signal for the mth filter, m=0,1, . . . M-1, &ggr; is a stability factor, and Gm=1 for m=0, and Gm=2 for mâ‰ 0.