Two-channel Audio Research Articles

The EarSAVAS Dataset

Subject-aware vocal activity sensing on wearables, which specifically recognizes and monitors the wearer's distinct vocal activities, is essential in advancing personal health monitoring and enabling context-aware applications. While recent advancements in earables present new opportunities, the absence of relevant datasets and effective methods remains a significant challenge. In this paper, we introduce EarSAVAS, the first publicly available dataset constructed specifically for subject-aware human vocal activity sensing on earables. EarSAVAS encompasses eight distinct vocal activities from both the earphone wearer and bystanders, including synchronous two-channel audio and motion data collected from 42 participants totaling 44.5 hours. Further, we propose EarVAS, a lightweight multi-modal deep learning architecture that enables efficient subject-aware vocal activity recognition on earables. To validate the reliability of EarSAVAS and the efficiency of EarVAS, we implemented two advanced benchmark models. Evaluation results on EarSAVAS reveal EarVAS's effectiveness with an accuracy of 90.84% and a Macro-AUC of 89.03%. Comprehensive ablation experiments were conducted on benchmark models and demonstrated the effectiveness of feedback microphone audio and highlighted the potential value of sensor fusion in subject-aware vocal activity sensing on earables. We hope that the proposed EarSAVAS and benchmark models can inspire other researchers to further explore efficient subject-aware human vocal activity sensing on earables.

Carrying Multichannel Audio in a Stereo Production and Distribution Infrastructure

As the demand for multichannel audio increases, handling 5.1 sound channels within today's two-channel audio infrastructure has become a significant issue. To address this need, a new coding system called Dolby E capable of carrying up to eight channels of audio through a traditional stereo infrastructure, has been developed. While this system is based on perceptual coding principles and audio data compression, it has also been designed to meet constraints imposed by operational practices of program production, such as video frame boundary editing and multigeneration use. This paper provides a technical overview of the system, describing the architecture and design of the encoder and decoder. It also details the work currently under way on standardizing how stereo broadcast equipment should handle and pass such signals, and the ways this technology is being made available to manufacturers of broadcast system components.

A real-time implementation of a stereophonic acoustic echo canceler

Teleconferencing systems employ acoustic echo cancelers to reduce echoes that result from the coupling between loudspeaker and microphone. To enhance the sound realism, two-channel audio is necessary. However, stereophonic acoustic echo cancellation (SAEC) is more difficult to solve because of the necessity to uniquely identify two acoustic paths, which becomes problematic since the two excitation signals are highly correlated. In this paper, a wideband stereophonic acoustic echo canceler is presented. The fundamental difficulty of stereophonic acoustic echo cancellation is described and an echo canceler based on a fast recursive least squares (FRLS) algorithm in a subband structure, with equidistant frequency bands, is proposed. The structure has been used in a real-time implementation, with which experiments have been performed. In this paper, simulation results of this implementation on real life recordings, with 8 kHz bandwidth, are studied. The results clearly verify that the theoretic fundamental problem of SAEC also applies in real-life situations. They also show that more sophisticated adaptive algorithms are needed in the lower frequency regions than in the higher regions.

Stereophonic acoustic echo cancellation and two-channel adaptive filtering: an overview

Stereophonic acoustic echo cancellation (SAEC), has been studied since the early 1990s. Because of spatial realism, two-channel audio is now becoming more interesting in a number of hands-free applications such as teleconferencing, multi-participant desktop conferencing, and televideo gaming. From a theoretical point of view, SAEC differs considerably from traditional mono echo cancellation since the normal equation to be solved by the adaptive algorithm is singular. Of course, this also affects the practical considerations that have to be made when designing a SAEC system, e.g. choice of adaptive algorithm. This paper reviews the basic theory behind SAEC, solutions to the singularity problem, and a number of classical two-channel adaptive algorithms suited to the problem. Copyright © 2000 John Wiley & Sons, Ltd.

Subjective evaluation of state-of-the-art two-channel audio codecs

The results of double-blind subjective tests are reported, which were conducted to examine the audio quality of several state-of-the-art two-channel audio codecs against a CD-quality reference. Implementations of the MPEG Layer 2, MPEG Layer 3, MPEG AAC, Dolby AC-3, and Lucent PAC codecs were evaluated at the Communications Research Centre in Ottawa, Canada, in accordance with the subjective testing procedures outlined in ITU-R Recommendation BS. 1116. The bit rates varied between 64 and 192 kbit/s per stereo pair. The study is unique in that this is the first time that these codecs have been compared in a single test. Clear results were obtained for comparing the subjective performance of the codecs at each bit rate. All codecs were software based and constituted the most current implementations at the time of testing. An additional hardware-based MPEG Layer 2 codec was included in the tests as a benchmark.

A better understanding and an improved solution to the specific problems of stereophonic acoustic echo cancellation

Teleconferencing systems employ acoustic echo cancelers to reduce echoes that result from coupling between the loudspeaker and microphone. To enhance the sound realism, two-channel audio is necessary. However, in this case (stereophonic sound) the acoustic echo cancellation problem is more difficult to solve because of the necessity to uniquely identify two acoustic paths. We explain these problems in detail and give an interesting solution which is much better than previously known solutions. The basic idea is to introduce a small nonlinearity into each channel that has the effect of reducing the interchannel coherence while not being noticeable for speech due to self masking.