IJSRD - International Journal for Scientific Research & Development| Vol. 3, Issue 01, 2015 | ISSN (online): 2321-0613 All rights reserved by www.ijsrd.com 344 Mode Selective Simulation for Noise Reduction in Digital Hearing Aid Kaveri Ratanpara 1 Priyank Shah 2 1,2 Department of Biomedical Engineering 1,2 Government Engineering College, Sector-28, Gandhinagar, Gujarat Abstract— Hearing aids are gadgets utilized by hearing hindered persons to balance the hearing loss. They can't totally beat the perceptual bends brought on by a hearing loss however support the user to decode speech. The focus of this paper is to develop simple Digital Hearing Aid (DHA) noise reduction model using MATLAB simulation and programming language that works in real time mode or offline mode. Implementation of the structured DHA system includes the DC blocking filter using MATLAB programming and adaptive noise reduction filter. Key words: DHA, MATLAB, Digital filter I. INTRODUCTION Today, a major part of human population suffering by hearing loss. The main complaint of person with hearing loss is low ability to deduce speech in noisy environment. So, by using the Digital Signal Processing (DSP) enhance the possibility of performing signal-to-noise ratio. The sound is processed by the hearing aid and reaching to ear. Essentially it is made of three parts, Microphone, Processor unit, receiver module. Electrical Impulse is converted by use of Microphone. Not it is converted in suitable form from electrical impulse by Processor unit; receiver converts the impulses in sound using a decoder. The audio frequency range is generally between 20 Hz to 20 kHz which capable to hear. The human ear is only sensible to hear the frequency range between 1 kHz to 4 kHz[1]. So below 1 kHz, ear will not respond and above the 4 kHz, it may damage the hearing capability. This paper shows design of simulink block model for digital hearing aid system with mode selecting technique. This simulink block model is works in both real time mode and offline mode. The simulation result of this system shows the noise removing output signal from the noisy input signal. This is possible by using the signal processing block sets through the simulink library. II. SIMULINK BLOCK MODEL FOR NOISE CANCELLATION IN DHA In this section mode selective simulink that is work in both real time and offline mode is shown (in figure 1). This simulink generally divided in to the 5 blocks: Input signal block, Dc blocking digital filter block, Noise source block, NLMS filter block, Output signal block. The simulink block model includes three switches and working of this is shown in table 1. In this switching mode switch no.1 (S1) is used for selecting real time mode and offline mode for input the signal, while switch no.2 (S2) is used for adding zero vector or random noise signal and switch no.3 (S3) is used for the NLMS algorithm output signal or desired signals. Selection If select 0 If select 1 Switch 1 Real time signal Signal from audio file Switch 2 Zero vector Noise signal Switch 3 NLMS output signal Desired signal Table 1: Switching Modes Fig. 1: Simulink block model for Noise cancellation in DHA A. Input Signal Block: This input signal block is divided in to the two sub blocks. One is from audio device block that is used to reads speech signal from an audio device in real time mode. This block is connected to the frame status function block for the frame conversion to set the sampling mode of the output signal. Source block parameter of from audio device block is shown in table 2. Second sub-block is signal from work space block that is used to take the audio file in offline mode from the MATLAB workspace at successive sample times. Both the sub blocks are connected to the multiport switch 1 function block to select the real time or offline mode.