Implementação de banco de filtros utilizando Modulated Lapped Transform para aplicação em prótese auditiva

Abstract

The present paper proposes the implementation and simulation of a filter bank using the Modulated Lapped Transfom (MLT) for application in hearing aids. Initially, a literature review about filter bank and block transformations was carried out, showing that block transforms have audible artifacts, necessitating the overlapping of the blocks. In this context, an implementation of a overlapped block transform known as MLT was carried out in a simulated environment. In view of this, a loss of auditory sensitivity was proposed according to an audiometry test. In this way, the filter bank simulations were developed in order to analyze the signal decomposition, the perfect reconstruction and the amplification in the required frequency bands. Signal decomposition was defined in 64 frequency bands by means of three methods of signal amplification. The first method is based on the critical bands of the human ear, the second method is based on the frequency bands used in the audiometry test and the third method by means of octave decomposition. The number of filters used for signal decomposition in the proposed problem presented satisfactory results. The reconstruction of the signal was evaluated and verified in the simulations for the filter bank without amplification. The gains were defined proportionally to the loss, and the verification was done graphically and audibly. Finally, the study allowed to verify that the hearing aid needs amplification in isolated frequency bands and that the filter bank presented in this work proved to be efficient for these needs.