NS Overview

The lib_ns library provides an API to implement Noise Suppression within an application.

The noise suppressor estimates the probability of speech presence and dynamically adapts its coefficients to estimate the noise levels to subtract from the input. The filter will automatically reset its noise estimations every 10 frames.

The NS takes as input a frame of data from an audio channel. This could be the microphone input or the output of another module in the application.

Noise Suppression is performed on a frame-by-frame basis. Each frame consists of 15ms of data, which is 240 samples at 16kHz input sampling frequency. Input data is expected to be in a fixed-point 32-bit 1.31 format.

Before processing any frames, the application must configure and initialise the NS instance by calling ns_init(). Then for each frame, ns_process_frame() will update the NS instance’s internal state and produce the output frame by applying the NS algorithm to the input frame.

If multiple channels need to be processed by the application, or multiple outputs are required, an independent instance of the NS must be run for each channel.