Study of Harmonics-to-Noise Ratio and Critical-Band Energy Spectrum of Speech as Acoustic Indicators of Laryngeal and Vo
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Research Article Study of Harmonics-to-Noise Ratio and Critical-Band Energy Spectrum of Speech as Acoustic Indicators of Laryngeal and Voice Pathology Kumara Shama,1 Anantha krishna,1 and Niranjan U. Cholayya2 1 Department 2 Department
of Electronics and Communication Engineering, Manipal Institute of Technology, 576104 Manipal, India of Biomedical Engineering, Manipal Institute of Technology, 576104 Manipal, India
Received 5 April 2005; Revised 5 January 2006; Accepted 13 January 2006 Recommended by Douglas O’Shaughnessy Acoustic analysis of speech signals is a noninvasive technique that has been proved to be an effective tool for the objective support of vocal and voice disease screening. In the present study acoustic analysis of sustained vowels is considered. A simple k-means nearest neighbor classifier is designed to test the efficacy of a harmonics-to-noise ratio (HNR) measure and the critical-band energy spectrum of the voiced speech signal as tools for the detection of laryngeal pathologies. It groups the given voice signal sample into pathologic and normal. The voiced speech signal is decomposed into harmonic and noise components using an iterative signal extrapolation algorithm. The HNRs at four different frequency bands are estimated and used as features. Voiced speech is also filtered with 21 critical-bandpass filters that mimic the human auditory neurons. Normalized energies of these filter outputs are used as another set of features. The results obtained have shown that the HNR and the critical-band energy spectrum can be used to correlate laryngeal pathology and voice alteration, using previously classified voice samples. This method could be an additional acoustic indicator that supplements the clinical diagnostic features for voice evaluation. Copyright © 2007 Hindawi Publishing Corporation. All rights reserved.
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INTRODUCTION
Diseases that affect the larynx cause changes in the patient’s vocal quality. Early signs of deterioration of the voice due to vocal malfunctioning are normally associated with breathiness and hoarseness of the produced voice. The first tool used to detect laryngeal pathology is subjective analysis of the speech. Trained physicians perform a subjective evaluation of the patient’s voice, which is followed by laryngeoscopy that may cause discomfort to the patient. A complementary technique could be acoustic analysis of the speech signal, which is shown to be a potentially useful tool to detect voice disease. This noninvasive technique is a fast low-cost indicator of possible voice problems. Any change in the anatomical structure because of pathology in turn results in physiological function that alters the vocal output [1–7]. The analysis methods found in the literature are mainly based on the periodicity of vocal fold vibration and the turbulence in the glottal flow resulting from malfunctioning of the vocal folds [8–17]. The periodicity perturbations are associated with the measurement of jitter and shimmer. Jitter is the variation between the successive
fundamental periods
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