Implementation of narrow-band noise algorithms according to ANSI S3.6-1996

Abstract

In order to generate narrow-band noise according to ANSI S3.6-1996 in an efficient way, it is necessary to employ multirate signal processing techniques. Thanks to the successive conversion of the sampling rate in the stages of the system, an efficient implementation of the required algorithms is obtained. These signals are entirely bandpass signals. The adopted solution is to design equivalent lowpass filters followed by a frequency modulation of the filtered signal with the purpose of moving it to the desired frequency. To obtain a better performance in the resulting filter, multistage structures have been used to achieve the required changes in the sampling rate to implement the lowpass filter by means of a multirate signal processing technique. A LabVIEW application have been implemented for designing these types of filters. This program generates the filter coefficients and offers the possibility of carrying out a simulation and saving these coefficients into a C header file. These filters have been successfully tested, on a new DSP based audiometer that uses TI TMS320C6701, by means of Code Composer Studio and a series of routines that implement each one of the stages that compose the filter.