China
Africa
Explore chapters and articles related to this topic
Physical analysis of multichannel sound field recording and reconstruction
Published in Bosun Xie, Spatial Sound, 2023
The analyses in Sections 9.1 and 9.3 indicate that Ambisonics is a physical scheme of the spatial sampling and reconstruction of a sound field. A microphone array is an effective method for the spatial sampling of a sound field, where the spatial information of sound field is recorded through the special configuration of multiple microphones. Under certain conditions, the spatial harmonic components of the sound field or independent signals of Ambisonics can be obtained by applying appropriate frequency and spatial filtering processing to microphone array outputs. Moreover, signals with other different directivities can be derived from the weighted combinations of microphone array outputs by appropriately choosing frequency-dependent weights. As stated in Sections 9.1 and 9.2, Ambisonic signal recording can be regarded as a beamforming method; therefore, Ambisonic driving signals can be obtained directly by applying beamforming processing to microphone array outputs. Beamforming aims to enhance the recorded outputs at the target direction and restrain the outputs in other directions. Signals recorded by a microphone array are also applicable to other multichannel sound reproduction and even binaural reproduction (Section 11.6.1). Therefore, a microphone array is a flexible method for sound field recording, as discussed in this section.
*
Published in Gillian M. Davis, Noise Reduction in Speech Applications, 2018
Some actual acoustic measurements are reported in the paper by Hoffman et al.21 They employ a four-microphone logarithmic array, 24.5 cm long, broadside on to the speech source. The outputs are processed by a generalized sidelobe canceller of their design. Their measurements show that, with a single interfering source, a SNR enhancement as much as 15 dB can be achieved. They found, however, that this performance level decreases as the talker direction and noise source direction get closer together. Their work illustrates that in order to get the best performance out of a given microphone array (as long as this is consistent with the manufacturer’s instructions), the user should try to arrange things so that talker, noise source, and array are as far from collinear as possible; in other words, the talker and noise should be roughly 90° apart relative to the array. Greater noise reduction is expected from arrays with more microphones (see “Delay-and-Sum Beamforming,” above).
Sensor Networking Software and Architectures
Published in John R. Vacca, Handbook of Sensor Networking, 2015
Microphone array can be thought as a concentrated arrangement of acoustic sensor that is designed to operate together in order to obtain some specific functionality that cannot be achieved using individual transducer only. In this sense, there are a variety of functions that can be performed by microphone arrays; these include the control of directivity pattern or beamforming, sound source localization, and blind source separation (BSS). Other applications such as speech enhancement and noise cancellation are achieved by combining the previously mentioned techniques.
Developing a framework for promoting physical activity in a Boccia game scenario
Published in Computer Methods in Biomechanics and Biomedical Engineering: Imaging & Visualization, 2019
Vinícius Silva, João Ramos, Pedro Leite, Filomena Soares, Paulo Novais, Pedro Arezes, Filipe Sousa, Carina Figueira, António Santos
The Microsoft V2 is composed by a 3D depth sensor, infrared emitters and receivers, a 1080p RGB camera and a microphone array. The depth sensor employs the time of light technique in order to track the user joints in real-time. The colour camera captures the RGB colour stream. Using the infrared information, the depth sensor is able to provide the corresponding depth image of the current scene. The microphone array allows to localise the sound sources in the space and to perform background noise cancellation. Through the Application Programming Interface (API) provided by Microsoft one is able to track up to six users’ body movements, extract facial features and recognise some gestures. This also provides access to the raw sensor data streams and to the skeletal tracking (Microsoft 2017).