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Acoustic Software



LRFTubes

Low Reduced Frequency Tubes

LRFTubes a Python computer program for computing one-dimensional acoustic waves in ducts and other lumped elements. LRFTubes is used by ASCEE for modeling:

  • Acoustic ducts and ventilation systems, to obtain first indications below the cut-on frequency of higher order acoustic modes, and optimize Helmholtz and quarter wave resonators and the like.
  • Modeling of the insertion loss of in-ear hearing protection systems
  • Modeling and designing the performance of micro-speakers for in-ear headphones (earphones)

These modeling efforts are done to reduce the amount of design trial and error procedures, effectively resulting in shorter design improvement cycles.

LRFTubes contains a large amount of pre-defined models, such as for (micro)speakers, ducts with several cross section types (circular, rectangular, narrow slits), transitions, cones, the IEC 711 ear coupler, etc, which quickly enables us to model your system. Moreover, we can use the code programmatically for optimization purposes.

LRFTubes is propietary code.


LASP

Library for Acoustic Signal Processing

LASP is a Python-C library for acoustic signal processing.

The main goal of this library will be the processing of data from an array of microphones real time, on a Raspberry PI. At the point in time of this writing, we are yet unsure whether the Raspberry PI will have enough computational power to this end, but may be by the time it is finished, we have a new faster generation :).

Current features that are implemented:

  • Compile-time determination of the floating-point accuracy (32/64 bit)
  • Fast convolution FIR filter implementation
  • IIR Filter implementation using BiQuad (second order) sections
  • Fractional octave filter banks
  • Sample rate decimation
  • Octave filterbank FIR and IIR filters designed to comply with IEC 61260 (1995) class 0.
  • Third octave filter bank FIR and IIR filters designed to comply with IEC 61260 (1995) class 0.
  • Averaged power spectra and power spectral density determination using Welch' method. Taper functions of Hann, Hamming, Bartlett and Blackman are provided.
  • A thread-safe job queue including routines to create worker threads.
  • Several linear algebra routines (wrappers around BLAS and LAPACK).
  • A nice debug tracer implementation
  • Slow and fast time updates of (A/C/Z) weighted sound pressure levels
  • A compile time choice to use either the FFTW Fast Fourier Transform backend, or the FFTPack backend.

Future features (wish-list)

  • Conventional- and delay-and-sum beam-forming algorithms
  • A peak level meter, conforming to IEC-60628-18

For now, the source code is well-documented but it requires some additional documentation (the math behind it). This will be published in a sister repository in a later stage.

If you have any question(s), please feel free to contact us: info@ascee.nl.