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BFLIB Middleware

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Highlights

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  • Robust beamforming algorithm descended from Functional and Adaptive Beamforming techniques

  • Very high dynamic range

  • High response rate

  • Seamless integration with acoustic camera systems

  • Includes functions for array simulation and delay and sum array spectrum and waveform with weights specified by the calling routine

  • Developed by leader in aeroacoustic beamforming

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Introduction

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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.

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Specifications

 

  • Acoustic medium:   -40° C and 85° C, giving a sound speed between 306 and 379 m/s  (assumes propagation in uniform, unbounded air)

  • Array shape options:  

    • Hard or open planar up to 2.5m diameter

    • Open spherical up to 0.7m diameter (Linear arrays and non-planar arrays other than complete spheres are excluded)

    • User specifies the array design within one of the two categories - plane or sphere.

    • RMS distance of the microphones from the center point (the average location) must be at least 0.05 m. 

    • Number of Microphones: 16-168

    • Microphone directivity: omnidirectional

  • Frequency range: up to 20 kHz 

  • Typical performance with OptiNav Beamforming in favorable situations (stationary, incoherent sources, decay time at least 0.3 s)

    • Dynamic range: 20-40 dB.

    • Resolution: better than the Rayleigh limit by a factor of 2-2.5.

    • Strong rejection of incoherent microphone self noise including boundary layer noise.

  • Sample rate supported: up to 96 kS/s

  • Block sizes (half of FFT transform length): 128, 256, 512, 1024, 2048, 4096

  • Processing band: frequency domain processing of broadband signals with three bandwidth options:

    • Narrowband: bandwidth = (sample rate)/(transform length)

    • 1/12 octave band

    • 1/3 octave band 

  • Beamforming grid: specified by giving an array of arbitrary 3D points.  

  • Beamforming algorithms: 

    • Conventional frequency domain beamforming

    • OptiNav Beamforming: Capon method with proprietary robustness modifications.

    • 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.

  • System requirements: Windows 7 or Windows 10 supporting at least 4 threads

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