BRP-PACU

BRP-PACU is a dual channel FFT audio analysis tool. It is designed to be used with an omnidirectional calibrated microphone to configure any sound system with an appropriate equalization and delay. It compares the output of the system to the input of the system to obtain the transfer function[1] of the system. These data allow one to perform final equalization using just the input/output of the DSP or any other device used for Equalization.

Theoretical basis

This software program uses a Transfer Function Measurement method to compare the output of a (unprocessed) loud-speaker system and room combination to the input signal which is usually filtered pseudorandom noise.[2] Because the sound has a propagation time from the exit point of the transducer to the measurement device, a delay must be inserted in the reference signal to compensate. This delay is automatically found by the software to aid in practical system measurement.

Supported platforms

Currently the only supported platforms are Linux and Mac OS X because it relies on POSIX Threads. It also is written using floating point processing, making most embedded Linux device support difficult.

Features
  • Four capture buffers, with auto-save (in case of crash) and save-as ability
  • Averages buffers to a separate buffer and flips it for analysis
  • Automatic delay calculation
  • Impulse response capturing
  • Uses JACK to route and manage audio paths
  • Pink Noise generation tool to eliminate need for an external Pink Noise source

Licensing and availability

The software is licensed under the GPL Version 2. It is available from sourceforge as C code.

Future development
  • Ubuntu and Debian packages
  • A Virtual Machine for usage under other Operating Systems such as Microsoft Windows
  • The ability to create and load User Interface options
  • Phase response for transfer function

References
  1. The transfer function is defined by in, e.g., Birkhoff, Garrett; Rota, Gian-Carlo (1978). Ordinary differential equations. New York: John Wiley & Sons. ISBN 0-471-05224-8.
  2. The basic principle of the transfer function analysis is a dual channel measurement where one channel is designated as "known" and the other channel is "unknown". , McCarthy, Bob (2007). Sound Systems: Modern Techniques and Tools for Sound System Design and Alignment. New York: Focal Press. ISBN 978-0-240-52020-9.
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