Noise Suppression Testing and Standards Leadership

Testing & Standards
To deliver clear voice communications in all environments, a noise suppression solution has to provide strong, consistent performance across all types of conditions. And a high quality solution must also minimize voice distortion or artifacts when suppressing noise and echoes.

Audience has taken a leading role in helping the industry identify testing standards for noise suppression solutions to validate performance in real world environments. Working closely with leading wireless service providers and handset manufacturers, Audience has helped to develop and modify recommendations for testing standards to manage objective and subjective assessments for noise suppression quality for the International Telecommunication Union (ITU). The ITU is the United Nations specialized agency in the field of telecommunications, information and communication technologies and its “Standardization Sector” (ITU-T) is responsible for studying technical and operating questions and setting recommendations to standardize telecommunication on a worldwide basis.

Recommendation ITU-T P.835 – Subjective Testing Standard
The ITU-T P.835 recommendation (approved in November 2003) provided a methodology to evaluate the subjective quality of speech in noise and to evaluate noise suppression algorithms, using separate rating scales to evaluate the subjective quality of the speech signal alone, the background noise alone, and overall quality – along three dimensions: signal distortion, noise distortion, and overall quality. But this focused on stationary noise only.

Audience worked closely with leading mobile operators and handset makers to ratify a new standard for a comprehensive test methodology to address subjective testing of non-stationary noise suppression. On October 2007, the ITU-T standardization committee approved Amendment I, Appendix III to enhance the P.835 standard and provide test methodologies to emulate real world conditions of multiple, fast-changing, non-stationary noise sources. This amendment was an important step in helping the mobile industry effectively evaluate the performance of noise suppression solutions in the busy environment mobile users encounter every day – and to ensure a high quality voice experience for customers. Click here to download the ITU-T P.835 Standard: Amendment 1, Appendix III.

Recommendation ITU-T G.160 – Objective Testing Standard
The ITU-T G.160 standard specified three objective metrics designed to appraise the performance of noise suppression algorithm: Total Noise-Level Reduction (TNLR), Signal-to-Noise Ratio Improvement (SNRI), and Delta Signal-to-Noise (DSN). Within these objective metrics, SNRI is the most indicative measure of noise suppression effectiveness. SNRI is measured during speech activity and factors in the relationship of the background noise level to the level of speech. It computes the Signal-to-Noise Ratio improvement achieved by the Noise Suppression algorithm – accounting for speech attenuation or amplification in addition to noise suppression. Some noise suppression algorithms attenuate the speech and the background noise at the same time, lowering the overall SNRI after applying noise suppression.

Audience was requested by the ITU committee to lead an effort to create an amendment to Appendix II of the G.160 standard to ensure that objective measurement methods and calculations were accurate in evaluating performance based on new technology for noise reduction systems. Amendment 1 of G.160 Appendix II was approved by the ITU in November 2009. Click here to download the ITU-T G.160 Standard: Amendment 1, Appendix II.

Audience conducts rigorous testing to ensure the quality of its noise suppression solutions under a wide variety of noise conditions, using the ITU-T test protocols, and continues to set performance benchmarks. And we’re continuing to work with industry groups to support the deployment of these test methodology standards to ensure the highest quality voice communications.