Improvement and Evaluation of Time-Spread Echo Hiding Technology for Long-Distance Voice Evacuation Systems

  • Akira NishimuraEmail author
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 10431)


Several improvements to the time-spread echo hiding method are proposed for an aerial audio data hiding in which speech signals are broadcast by the outdoor loudspeakers of a voice evacuation and mass notification system. Evaluations of the data hiding system for speech signals were conducted using computer simulations including several disturbances caused by the long-distance (from 70 to 800 m) aerial transmission of sounds. The frequency response of a distant horn-array loudspeaker system, the absorption of sound by the atmosphere, reverberation and a single long-path echo, a constant frequency shift that mimics a small Doppler shift and a mismatch of sampling frequencies between sending and receiving devices, and additive background noise are simulated as disturbances. A background noise recorded outdoors was mixed to simulate a loud outdoor space in a city at signal-to-noise ratios of −5, 0, and 5 dB. The computer simulation results showed that the suppression of high- and low-frequency regions in the logarithmic spectral domain in the decoding process was significantly effective for the decoding performance. A novel hiding method of the alternating sign of echoes was moderately effective under relatively high SNR (0 and 5 dB) conditions.


Bilateral symmetric time-spread echo Frequency response Absorption by the atmosphere Reverberation Long-path echo 



This study was partially supported by TOA Corporation. The author thanks the anonymous reviewers for their helpful comments and suggestions on this manuscript.


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Copyright information

© Springer International Publishing AG 2017

Authors and Affiliations

  1. 1.Department of Informatics, Faculty of InformaticsTokyo University of Information SciencesChibaJapan

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