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Open AccessArticle

Speech Enhancement for Secure Communication Using Coupled Spectral Subtraction and Wiener Filter

1
Research Center for Informatics, Indonesian Institute of Sciences, Jawa Barat 40135, Indonesia
2
Department of Electrical Engineering, University of Indonesia, Jawa Barat 16424, Indonesia
*
Author to whom correspondence should be addressed.
Electronics 2019, 8(8), 897; https://doi.org/10.3390/electronics8080897
Received: 28 June 2019 / Revised: 5 August 2019 / Accepted: 13 August 2019 / Published: 14 August 2019
(This article belongs to the Section Computer Science & Engineering)
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Abstract

The encryption process for secure voice communication may degrade the speech quality when it is applied to the speech signals before encoding them through a conventional communication system such as GSM or radio trunking. This is because the encryption process usually includes a randomization of the speech signals, and hence, when the speech is decrypted, it may perceptibly be distorted, so satisfactory speech quality for communication is not achieved. To deal with this, we could apply a speech enhancement method to improve the quality of decrypted speech. However, many speech enhancement methods work by assuming noise is present all the time, so the voice activity detector (VAD) is applied to detect the non-speech period to update the noise estimate. Unfortunately, this assumption is not valid for the decrypted speech. Since the encryption process is applied only when speech is detected, distortions from the secure communication system are characteristically different. They exist when speech is present. Therefore, a noise estimator that is able to update noise even when speech is present is needed. However, most noise estimator techniques only adapt to slow changes of noise to avoid over-estimation of noise, making them unsuitable for this task. In this paper, we propose a speech enhancement technique to improve the quality of speech from secure communication. We use a combination of the Wiener filter and spectral subtraction for the noise estimator, so our method is better at tracking fast changes of noise without over-estimating them. Our experimental results on various communication channels indicate that our method is better than other popular noise estimators and speech enhancement methods. View Full-Text
Keywords: secure voice communication; speech enhancement; noise estimation; Wiener filter; spectral subtraction secure voice communication; speech enhancement; noise estimation; Wiener filter; spectral subtraction
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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MDPI and ACS Style

Pardede, H.; Ramli, K.; Suryanto, Y.; Hayati, N.; Presekal, A. Speech Enhancement for Secure Communication Using Coupled Spectral Subtraction and Wiener Filter. Electronics 2019, 8, 897.

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