Microphone transfer function adaptation using a Bi - Quad filter and DCL
Adaptacija prenosne funkcije mikrofona z Bi - Quad filtrom in DCL

english

2008

volume 38, issue 2

Strokovno društvo za mikroelektroniko, elektronske sestavne dele in materiale

A suitable adaptation of the microphone in the audio path of a mobile device is a very sensitive tasks. The conformation of the frequency response characteristic to the GSM standards is inevitable. Achieving the highest correlation between the specified GSM frequency response specification with the microphone and speaker characteristic is a delicate matter. In this paper we will present tests performed for microphone transfer function adaptation on a mobile phone using a Bi-Quad filter. Therefore a cascading with a IIR filter of the 11. order was applied. The main goal of our test was to evaluate the influence of a recursive filter in the audio input path to the recognition rate of the embedded recognizer. The focus of our tests was to simulate the cascaded components with only one substitute having similar (almost equivalent) frequency response characteristics. By doing so we assumed that the microphone used was a high quality microphone with a linear frequency response. Further enhancement of the audio quality was performed by a more sophisticated dynamic compression and limitation algorithm (DCL). For the evaluation tests the Motiv and Aurora 3 databases were applied to the audio input. The tests have shown that with appropriate adaptation of the cascaded components an improvement of the recognition rate is realizable. The recognition rate of the mobile phone embedded recognizer was enhanced for over 6% indicating that the proposed approach sensibly contributes to speech signal enhancement.

18.12.2015