Pulse compression techniques and array focusing are common ways to achieve better signal-to-noise (SNR) levels for reception while maintaining the resolution of a short pulse. These techniques can inadvertently create a near surface blind region due to longer transmit events and are limited by available instantaneous transmit power. Furthermore, the increased complexity at high voltage levels makes implementations more costly. An alternative to these methods is binary modulation of a predetermined signature excitation waveform. Using both computer simulation and physical experiments, this technique is shown to decouple the pulse duration versus resolution compromise even if available power is fixed. The method’s effectiveness allows for the reduction of the outgoing excitation pulse amplitude driving a conventional transducer probe that is normally of the order of hundreds of volts to voltages on the order of 1 volt peak-to-peak. These results are achieved while maintaining the scan resolution and improving SNR by amounts in excess of 30 dB. Near surface anomalies are resolved despite arbitrarily long excitations as transmission and signal recovery occur simultaneously. The recovered system response from the binary modulation technique is able to discriminate against off-path reflection sources that would otherwise appear as in-line irregularities. Reducing off-angle anomalies inherently improves imaging performance in a heterogeneous environment as energy from the off-angle heterogeneities does not effectively contribute to noise in the demodulated scan result. Demodulation into in-phase and quadrature components also provides two linearly independent acoustic parameters yielding the material makeup of anomalies. Verification is performed with conventional, nondestructive testing, ultrasonic transducers.
 Misaridis, T. and Jensen, J., 2005, "Use of modulated excitation signals in medical ultrasound. Part I: basic concepts and expected benefits", IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 52(2), pp. 177-191.
 Pollakowski, M. and Ermert, H., 1994, "Chirp signal matching and signal power optimization in pulse-echo mode ultrasonic nondestructive testing", IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 41(5), pp. 655-659.
 Hartley, R., 1928, "Transmission of Information 1", Bell System Technical Journal, 7(3), pp. 535-563.
 Shannon, C., 1949, "Communication in the Presence of Noise", Proceedings of the IRE, 37(1), pp. 10-21.
 Viterbi, A., 2001, CDMA, Addison-Wesley, Reading, Mass. [u.a.].
 Costa, N. and Haykin, S., 2010, Multiple-Input Multiple-Output Channel Models, John Wiley & Sons, Hoboken.
 Kay, S., 1998, Fundamentals of statistical signal processing, PTR Prentice-Hall, Englewood Cliffs, N.J.
 Derode, A., Larose, E., Tanter, M., de Rosny, J., Tourin, A., Campillo, M., and Fink, M., 2003, "Recovering the Green’s function from field-field correlations in an open scattering medium (L)", The Journal of the Acoustical Society of America, 113(6), p. 2973.
 Welch, L., 1974, "Lower bounds on the maximum cross correlation of signals (Corresp.)", IEEE Transactions on Information Theory, 20(3), pp. 397-399.
 Kasami, T., 1966, Weight Distribution Formula for Some Class of Cyclic Codes, Coordinated Science Laboratory, University of Illinois at Urbana-Champaign.
 Dinan, E. and Jabbari, B., 1998, "Spreading codes for direct sequence CDMA and wideband CDMA cellular networks", IEEE Communications Magazine, 36(9), pp. 48-54.
 Claerbout, J., 1968, "SYNTHESIS OF A LAYERED MEDIUM FROM ITS ACOUSTIC TRANSMISSION RESPONSE", GEOPHYSICS, 33(2), pp. 264-269.
 Guillermin, R., Lasaygues, P., Sessarego, J., and Wirgin, A., 2001, "Inversion of synthetic and experimental acoustical scattering data for the comparison of two reconstruction methods employing the Born approximation", Ultrasonics, 39(2), pp. 121-131.
 Wapenaar, K., 2004, "Retrieving the Elastodynamic Green's Function of an Arbitrary Inhomogeneous Medium by Cross Correlation", Physical Review Letters, 93(25).
 Snieder, R., Miyazawa, M., Slob, E., Vasconcelos, I., and Wapenaar, K., 2009, "A Comparison of Strategies for Seismic Interferometry", Surveys in Geophysics, 30(4-5), pp. 503-523.
 “GNU Octave” GNU Octave: A Scientific Programming Language. [Online]. Available: http://www.gnu.org/software/octave/. [Accessed: 01-Mar-2017].
 “k-Wave,” k-Wave: A MATLAB toolbox for the time domain simulation of acoustic wave fields. [Online]. Available: http://www.k-wave.org/. [Accessed: 01-Mar-2017].
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