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Acoustic Software

This page provides an overview of our available 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

Library for Acoustic Signal Processing

Welcome to LASP: Library for Acoustic Signal Processing. LASP is a C++ library with a Python interface which is supposed to acquire and process (multi) sensor data in real time on a PC and output results.

Current features that are implemented:

  • Communication with data acquisition (DAQ) devices, of which:
  • Internal sound cards via the RtAudio backend. Many thanks to Gary P. Scavone et al.
  • Measurement Computing DT9838A signal analyzer.
  • Configuration of DAQ devices: AC coupling, IEPE, sensitivity physical quantities.
  • Recording of signals from these DAQ devices, and storing in a HDF5 file.
  • Filter designers to create A/C sound pressure weighting
  • Biquad filter designers for low pass, high pass, peaking and notch filters
  • A Peak Programme Meter (PPM) to monitor signal levels from DAQ and to watch for signal clipping.
  • A signal generator to create sine waves, sweeps and noise (white / pink).
  • Equalizers to equalize the output prior to sending.
  • Averaged power spectra and power spectral density determination using Welch' method. Taper functions of Hann, Hamming, Bartlett and Blackman are provided.
  • (One third) octave filter bank filters designed to comply with IEC 61260 (1995).
  • Slow and fast time updates of (A/C/Z) weighted sound pressure levels
  • Full Sound Level Meter implementation
  • Real time Sound Level meter, Power / Transfer function estimator
  • Spectra data smoothing algorithms
  • Sensor calibration for microphones

Future features (wish-list)

  • Conventional and delay-and-sum beam-forming algorithms
  • Impedance tube measurement processing

For now, the source code is well-documented on lasp.ascee.nl but it requires some additional documentation (the math behind it). This is maintained in a sister repository lasp-doc.

Troubleshooting

UlDAQ device not found on Linux

Run the following commands in the LASP main directory:

  • sudo cp third_party/uldaq/rules/50-uldaq.rules /etc/udev/rules.d/
  • sudo udevadm control --reload-rules

Then, unplug and replug the device and it should work.

Installation

For installation instructions, please visit INSTALLATON.md. If you have any question(s), please feel free to contact us: email.