Sistema para detecção de limiar auditivo fisiológico com base no pontecial evocado em regime permanente

• Ano de defesa: 2009
• Autor(a) principal: Matheus Wanderley Romao
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Minas Gerais; UFMG
• Palavras-chave em Português: Engenharia Elétrica; Engenharia elétrica
• Link de acesso: http://hdl.handle.net/1843/BUOS-8D2MEK

The auditory evoked potentials based on steady state response (ASSR) has shown a promising technique to assess the hearing thresholds in an objective way, especially in patients who cannot respond to conventional tests (such as newborns and people with cognitive disorders). Recently, several studies aim to improve the quality of the responses and, consequently, lead to shorter detection time. However, the devices available do not allow the user to investigate the effect that new waveforms, as well as other signal processing techniques, have on the performance of ASSR. This work aims to develop a system to investigate the ASSR under different paradigms to find a better and faster estimation of the physiological hearing threshold. The prototype is composed of a microprocessor system that uses the ADSP-BF533 (Analog Devices-USA) evaluate board to generate the auditory stimuli and to digitalize the electroencephalographic signals (EEG). It also has an amplifier, responsible for the analog EEG acquirement of brain electrical activity during stimulation and the response detection algorithm. A graphical user interface was designed to assist the user in the definition of the entire stimulation protocol (type of stimulus, stimulus duration, stimulus intensity, among others). The system can generate the most used waveforms - AM (amplitude modulation), FM (Frequency Modulation), MM (mixed modulation) and the Chirp tones. Moreover, the prototype allows the user to implement an arbitrary waveform. To evaluate the performance of the system, simulations and experiments were performed in 5 normal-hearing subjects. They were presented to AM stimuli of 80dBSPL intensity for about 22 minutes. The results showed that the detection algorithms implemented were able to identify the ASSR after approximately two minutes of stimulation. The system was able to identify the ASSR and it is going to be used in a larger population, in future works, to assess the physiological hearing threshold.