BFLIB Middleware
Highlights
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Robust beamforming algorithm descended from Functional and Adaptive Beamforming techniques
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Very high dynamic range
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High response rate
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Seamless integration with acoustic camera systems
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Includes functions for array simulation and delay and sum array spectrum and waveform with weights specified by the calling routine
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Developed by leader in aeroacoustic beamforming
Introduction
The OptiNav BFLIB software solution is a middleware software component optimized for aeroacoustic applications. The BFLIB is easy to integrate with acoustic cameras and can accurately identify acoustic sources. BFLIB represents decades of development and refinement.
Specifications
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Acoustic medium: -40° C and 85° C, giving a sound speed between 306 and 379 m/s (assumes propagation in uniform, unbounded air)
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Array shape options:
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Hard or open planar up to 2.5m diameter
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Open spherical up to 0.7m diameter (Linear arrays and non-planar arrays other than complete spheres are excluded)
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User specifies the array design within one of the two categories - plane or sphere.
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RMS distance of the microphones from the center point (the average location) must be at least 0.05 m.
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Number of Microphones: 16-168
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Microphone directivity: omnidirectional
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Frequency range: up to 20 kHz
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Typical performance with OptiNav Beamforming in favorable situations (stationary, incoherent sources, decay time at least 0.3 s)
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Dynamic range: 20-40 dB.
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Resolution: better than the Rayleigh limit by a factor of 2-2.5.
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Strong rejection of incoherent microphone self noise including boundary layer noise.
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Sample rate supported: up to 96 kS/s
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Block sizes (half of FFT transform length): 128, 256, 512, 1024, 2048, 4096
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Processing band: frequency domain processing of broadband signals with three bandwidth options:
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Narrowband: bandwidth = (sample rate)/(transform length)
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1/12 octave band
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1/3 octave band
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Beamforming grid: specified by giving an array of arbitrary 3D points.
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Beamforming algorithms:
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Conventional frequency domain beamforming
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OptiNav Beamforming: Capon method with proprietary robustness modifications.
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Both methods determine the Cross Spectral Matrix using Welch’s method with a Hanning window and 50% block overlap and an exponential filter for temporal integration.
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System requirements: Windows 7 or Windows 10 supporting at least 4 threads