Quality Analog Scramblers Using Frequency-Response Masking Filter Banks

A very low complexity frequency-domain analog speech scrambler having high-quality speech reconstruction is proposed. The scrambler uses frequency-response masking filter banks which have low computational complexity and narrow transition widths. The proposed system does not require bandwidth expansion, and is robust for transmission channels with distortion characteristics. Preliminary investigations showed that speech scrambled using this method is nearly unintelligible to the casual eavesdropper.

[1]  Alan L. Mackay,et al.  The Code Breakers , 1984 .

[2]  Nikil Jayant,et al.  Analog scramblers for speech privacy , 1982, Comput. Secur..

[3]  Y. Lim,et al.  FIR filter design over a discrete powers-of-two coefficient space , 1983 .

[4]  Yong Ching Lim,et al.  Efficient Implementation of the Fast Filter Bank For Critically Decimated Systems , 2006, APCCAS 2006 - 2006 IEEE Asia Pacific Conference on Circuits and Systems.

[5]  R. V. Cox,et al.  Analog scramblers for speech based on sequential permutations in time and frequency , 1983, The Bell System Technical Journal.

[6]  Jun Wei Lee,et al.  Efficiency in Audio Processing: Filter Banks and Transcoding , 2007 .

[7]  Nuggehally Sampath Jayant,et al.  A Comparison of Four Methods for Analog Speech Privacy , 1981, IEEE Trans. Commun..

[8]  Allen Gersho,et al.  Advances in speech coding , 1991 .

[9]  Yong Ching Lim,et al.  A multiplierless filter bank with deep stopband suppression and narrow transition width , 2005, 2005 IEEE International Symposium on Circuits and Systems.

[10]  Randy G. Goldberg,et al.  A Practical Handbook of Speech Coders , 2000 .

[11]  Ahmet M. Kondoz,et al.  Digital Speech: Coding for Low Bit Rate Communication Systems , 1995 .

[12]  Aaron D. Wyner.  An analog scrambling scheme which does not expand bandwidth, Part I: Discrete time , 1979, IEEE Trans. Inf. Theory.

[13]  Thomas P. Barnwell,et al.  Speech Coding: A Computer Laboratory Textbook , 1995 .

[14]  Yong Ching Lim,et al.  Frequency-response masking approach for the synthesis of sharp linear phase digital filters , 1986 .

[15]  Behrouz Farhang-Boroujeny,et al.  Adaptive filtering in subbands: Design issues and experimental results for acoustic echo cancellation , 1997, Signal Process..

[16]  Ronald W. Schafer,et al.  Digital Processing of Speech Signals , 1978 .

[17]  Yong Ching Lim,et al.  Fast filter bank (FFB) , 1992 .

[18]  Nuggehally S. Jayant.  Signal Compression - Coding of Speech, Audio, Image and Video , 1997 .

[19]  Schuyler Quackenbush,et al.  Objective measures of speech quality , 1995 .

[20]  R. Crochiere,et al.  Speech Coding , 1979, IEEE Transactions on Communications.

[21]  Mark J. T. Smith,et al.  Low delay FIR filter banks: design and evaluation , 1994, IEEE Trans. Signal Process..

[22]  AARON D. WYNER.  An analog scrambling scheme which does not expand bandwidth, Part II: Continuous time , 1979, IEEE Trans. Inf. Theory.

[23]  Say Wei Foo,et al.  Application Of Fast Filter Bank For Transcription Of Polyphonic Signals , 2003, J. Circuits Syst. Comput..

[24]  Kuldip K. Paliwal,et al.  Speech Coding and Synthesis , 1995 .

[25]  F. Mintzer,et al.  On half-band, third-band, and Nth-band FIR filters and their design , 1982 .

[26]  J. W. Lee,et al.  Efficient implementation of real filter banks using frequency response masking techniques , 2002, Asia-Pacific Conference on Circuits and Systems.