Enhancement of noise-suppressed speech by spectral processing implemented in a digital signal processor Hajer Rahali 1 • Zied Hajaiej 1 Received: 22 November 2016 / Revised: 26 April 2017 / Accepted: 4 September 2017 Ó Springer Science+Business Media, LLC 2017 Abstract This paper presents a noisy suppressed speech enhancement method by combining the basic spectral subtraction technique and spectral processing in the fre- quency domain to provide better noise suppression as well as better enhancement in the speech regions. In contrast to several previous approaches we do not try to achieve a complete removal of the noise, but instead our goal is to preserve a pre-defined amount of the original noise in the processed signal. This is accomplished by exploiting the masking properties of the human auditory system. The proposed algorithm is named PM ‘‘Proposed Method’’ which simulates properties of the human auditory system and applies it to the speech recognition system to enhance its robustness. The performance of the speech enhancement algorithm using the proposed masking model was com- pared with three other speech enhancement methods over 4 different noise types and five SNRs. The performances of the proposed approach are objectively and subjectively compared to the conventional approaches to highlight the aforementioned improvement. In this paper we discuss the design and development of a digital signal processor (DSP) implementation to achieve real-time performance of our filter. The target processor is a Texas Instruments TMS320C6713 floating point DSP. Keywords Speech enhancement  Digital signal processing  Psychoacoustic masking  Subjective test  Objective test 1 Introduction The enhancement of noisy speech has gained an increasing interest in recent years. This is mainly due to the driving forces in the area of mobile communications, where speech enhancement algorithms could be integrated in e.g. hands- free telephony devices. Many perceptual speech enhancement algorithms have been reported in the literature. They are based on psy- choacoustic models to take advantage of the masking phenomenon inherent to the human auditory system. For example, in [1] the psychoacoustic model is used to control the parameters of the spectral subtraction [2] in order to find the best trade-off between noise reduction and speech distortion; to make musical noise inaudible, the linear estimator proposed in [3] incorporates the masking prop- erties of the human auditory system. Although this method reduces the noise and improves the signal-to-noise ratio (SNR), it mostly tends to introduce speech distortion and a perceptually annoying residual noise usually called musical noise. The objective of this paper is to develop a novel speech enhancement algorithm exploiting simultaneous masking properties in very noisy conditions. The first contribution of this letter is to highlight the relevance of our phe- nomenon. The second contribution is the presentation of an elementary approach that takes into account this phe- nomenon to perform perceptual speech enhancement. The evaluation is done on the TIMIT database and dif- ferent types of background noises from the NOISEX-92 [4] & Hajer Rahali Hajer.Rahali@enit.rnu.tn Zied Hajaiej Zied.hajaiej@enit.rnu.tn 1 Laboratory of Signal, Image and Information Technologies, National Engineering School of Tunis, BP 37, 1002 Le Belve ´de `re, Tunis, Tunisia 123 Analog Integr Circ Sig Process DOI 10.1007/s10470-017-1042-z