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Paper data
SSB-Carrier Mismatch Detection from Speech Characteristics: Extension beyond the Range of Uniqueness

Heute Ulrich, LNS/TF/Univ. of Kiel
Guelzow Thomas, LNS/TF/ Univ. of Kiel,D-24143 Kiel, Germany
Kolb Hans-Joachim, MEDAV GmbH,D-91080 Uttenreuth,Germany

Page numbers in the proceedings:
Volume I pp 495-498

Echo Cancellation and Speech Enhancement

Paper abstract
In certain radio-surveillance applications, speech signals with uncertain carrier frequencies may be detected. Beyond other disturbances, carrier mis- matches distort the demodulated SSB signals by frequency shifts Df. Recently, a detection and correction of such errors was presented [1], exploit- ing the harmonic structure of voiced speech with a fundamental (or "pitch") frequency fp. Noise-robust, modified pitch-detection methods [2,3] were shown to be applicable, together with an iteratively corrected "coherent- superposition" algorithm [4,5]. Thereby, carrier errors are corrected reliably [1] - though only within an a-priori uniqueness range |Df| < fp/2. In the paper, the extension beyond this limitation is presented. It emerges from a closer, statistical analysis of the measurement errors: The measurement statistics within this range are interpreted as a conditional probability densi- ty function (pdf) pDf (x|y) conditioned on the actual pitch frequency, its combination with the (measurable) pitch-frequency pdf pfp(y) yields the joint pdf pDf,fp (x,y), and its integration gives the marginal pdf pDf (x). These considerations lead to an even narrower reliability range |Df| < fp/3, first. The interpretation of the uniqueness range as one period of an fp-periodic repetition of the measurement statistics, however, leads to the solution: After the same steps as sketched above, the marginal pdf pDf (x) shows a strong peak at the true value Df without a (theoretical) restriction. The resulting algor- ithm was successfully tested with simulated and real data.

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