Complex Cepstrum Processing of Digitized Transient Calibration Data for Removal of Echoes.
Abstract
The complex cepstrum technique was investigated for possible use in removing echoes casued by early reflections when low-frequency, peaked-response transducers are calibrated with transient signals. The calibration environment permits a high signal-to-noise ratio and a free choice of input waveforms, both of which are advantages in complex cepstrum processing. The proper method of computation with this technique is discussed in detail. Cepstrum filtering methods are discussed. Synthetic measurement data produced by a J9 projector driven with a damped sinusoidal pulse and a pressure-release reflection are shown, and real measurement data from a low-frequency line array driven by a single-cycle sinusoid with complex surface and bottom reflections are also shown. In both the synthetic and the real data, the echoes were successfully removed using the complex cepstrum technique. Data were digitized directly and stored on digital magnetic tape. Oversampling was reduced by sifting to achieve the correct sampling rate required by the complex cepstrum method. The results indicate that echo removal performed by complex cepstrum processing can be accurate enough to have potential usefulness in calibration procedures. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 30, 1977
- Accession Number
- ADA047414
Entities
People
- Lynn B. Poche Jr.
Organizations
- United States Naval Research Laboratory