| 摘要 |
Methods and apparatus are described for improving the cross correlation of three or more signals (e.g. acoustic logging signals) derived in an investigation of a borehole. The technique involves the testing of signs of samples employed in forming a cross-product during a cross- correlation. Sign conditions representative of a good match are so recognized and the resulting cross- product modified (by weighting) if needed for constructive contribution to the cross-correlation. Sign conditions indicative of a lack of correspondence between samples can also be detected so that cross- products from such samples can be prevented from adding to correlation peaks when an even number of negative samples are present. |
