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50 Years of Acoustic Signal Processing for Detection: Coping with the Digital Revolution
April-June 2005 (vol. 27 no. 2)
pp. 65-78
The authors describe their experiences, over five decades, in the digital signal processing revolution. Collaborating with BBN scientists from other disciplines, they have been challenged to find the best technical solutions to a given problem. The area addressed is acoustic signal processing for detecting the source of acoustic energy. Examples are monitoring airport noise and detecting sound from submarines in the oceans.

1. L.L. Beranek, Noise and Vibration Control, chapters 3, 4, and 5; McGraw-Hill, 1971, pp. 45-137.
2. D. Noiseux, "Variable Time Delay Drum," BBN Report 1119, Dec. 1963.
3. H. Fox and E. Starr, "Description of BBN 339A Bilateral Log Converter," BBN Report 680, Oct. 1959.
4. For a description and history of SOSUS, see biblio_sosus.html
5. K.D. Kryter, "The Meaning and Measurement of Perceived Noise Level," Noise Control, vol. 6, no. 5, 1960, pp. 12-17.
6. K.D. Kryter and K. Pearsons, "Some Effects of Spectral Content, Duration and Rise Time on Perceived Noise," BBN Report 965, Dec. 1962.
7. E. Starr, "Measuring Noise Pollution," IEEE Spectrum, vol. 9, no. 6, 1972, pp. 18-25.
8. Work by Fletcher and Munson in the early 1930s had defined equal loudness contours vs. frequency for humans. These curves formed the basis of the other weightings for sound level meters, as shown in Figure 1. H. Fletcher and W.A. Munson, "Loudness, Its Definition, Measurement and Calculation," J. Acoustical Soc. of America, vol. 5, October 1933, pp. 82-108.
9. G. Bell, C. Mudge, and J. McNamara, Computer Engineering, a DEC View of Hardware System Design, Digital Press, 1978.
10. D. Steele, R. Wagner, and E. Starr, "Design of the Instrumentation Center for Matapan Hydro-acoustic Noise Measurements," BBN Report 2162, Mar. 1971.
11. R.B. Blackman and J.W. Tukey, The Measurement of Power Spectrum from the Point of View of Communications Engineering, Dover, 1959.
12. Information processing as used in this article generally includes computer-based algorithms for detection of signals, their characterization and classification, grouping of detections which have all come from the same target, and tracking the targets.
13. Some information processing capabilities were intended to run only on the PDP-10. BBN designed one such information processing program to identify and track targets among the copious signal processing data. The Octopus tracker was the first practical use of Kalman filtering on measurements of uncertain origin (from the target of interest, other targets, or clutter). The Octopus project had actually begun before the ARC program, but the project found a strong home in the ARC. Octopus used a Bayesian approach to associate uncertain, asynchronous, heterogeneous measurements (bearings and time delay differences) with targets, displaying position estimates, and error ellipses on a geographic display. This Probabilistic Data Association Filter became the key algorithm and is described in a textbook co-authored by BBNer Tom Fortmann and consultant Yaakov Bar-Shalom: Y. Bar-Shalom and T.E. Fortmann, Tracking and Data Association, Academic Press, 1988.
14. J. Nitsche and J. Waters;, "The Detection of ASW Aircraft by Their Underwater Acoustic Signatures— A Theoretical and Experimental Investigation (U)," Proc. 29th Navy Symp. Underwater Acoustics, Vol. 2, USN Office of Naval Research, Nov. 1972, pp. 111-128. Confidential.
15. J.J. Barger, J.R. Nitsche, and D. Sachs, "Sound Transmission through the Sea Surface," J. Acoust. Soc.of America, Nov. 1976, Supplement No. 1, Fall 1976, pp. S35 (A).
16. J.R. Nitsche, J. O'Connor, and J. Bigler, "A Comparative Estimate of the Underwater Detectability of the P-3 and S-3 Aircraft (U)," Proc 32nd Navy Symp. Underwater Acoustics, vol. 2, USN Office of Naval Research, Nov. 1978, pp. 407-418. Confidential.
17. The BQQ-5 was the designation of the sonar system installed on US Attack Submarines at that time. The TB-29 towed-line array used was part of the BQQ-5 system.
18. D. Steele et al., "AUSEX Brassboard Processing System," BBN Report 4497, Nov. 1980.
19. H. Briscoe and E. Starr, "Post-Test Analysis Detection Results," BBN Report 4496, Nov. 1980.
20. In 1986 the Walker brothers (US Navy personnel) were convicted as spies for giving US Navy classified information to the Soviets. Many in the ASW community speculated that from this information the Soviets learned of the acoustic vulnerability of their submarines, and were then motivated to invest in quieting their newer submarines, such as the Akula class. See T. Parrish, The Submarine: A History, Viking, 2004, p. 488.
21. The underwater part of the ARAIDNE project was canceled during this time due to technical difficulties. The BBN ARAIDNE shore signal and information processing design was adapted to be an advance development model for the exploratory phase of the Fixed Distributed System, the designation of the replacement to the SOSUS system.

Index Terms:
Undersea detection, signal processing, acoustic processing, airport noise measurement, acoustic measurement, Acoustic Research Center, AUSEX, Fixed Distributed System
Richard F. Estrada, Edward A. Starr, "50 Years of Acoustic Signal Processing for Detection: Coping with the Digital Revolution," IEEE Annals of the History of Computing, vol. 27, no. 2, pp. 65-78, April-June 2005, doi:10.1109/MAHC.2005.16
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