Adaptive Noise Cancellation Filter Research Articles

The Effect of Hard Limiters on Signal Detection in Harmonic Noise Using Adaptive Noise Cancellation

Adaptive digital f ilters have been shown to be useful in reducing the power of harmonic noise in distribution line communication systems. Many DLC systems currently in use employ hard limiters to reduce this type of noise prior to detection of the signal. This research shows that the adaptive noise cancellation filter can be used effectively in tandem with hard limiters. The optimal, limit of the limiter is determined in the cases of the presence and absence of the adaptive noise canceller.

A unified approach to speaker verification with noisy speech inputs

Several speaker verification techniques based on different features of the human voice and with verification accuracy better than 99% have been proposed in the literature. Most of these systems work well only when the reference and test speech utterances are recorded under the same relatively noise-free conditions. The goal of this study was to develop a speaker verification system based on an orthogonal linear prediction model, that adopts a unified approach by utilizing only one set of reference parameters irrespective of whether the test speech data is of high quality or noise corrupted. Initial investigations reveal that significant improvement in accuracy is achieved if the verification algorithm utilizes only those parameters that are least sensitive to additive broadband noise. However, for reference and test utterances spoken over the telephone, satisfactory verification is realized only when all the orthogonal parameters are utilized in distance computation. It is finally shown that a significant improvement in accuracy is realizable if the test utterances (whether corrupted by additive noise or by passage through noisy telephone channels) are preprocessed by a modified adaptive noise cancellation filter.

Adaptive noise cancellation with a SAW storage correlator

A Sezawa wave storage correlator was used to implement an adaptive filter for noise cancellation. The filter reduced the level of a 150 MHz CW jamming signal by 26 dB and a broadband Sezawa wave convolver was used to compress an underlying chirp signal. The tap weights are determined in 40 to 100 μs, depending on the jamming signal power and feedback gain.