Monday, April 13, 2015

How-to: Measure Impulse Response with Aliki

Aliki is software to measure room impulse response. It's free and open source. On a dynamic system, impulse response is its output(response) when presented with a brief input signal (impulse). For room acoustic, impulse response can be used to measure acoustic characteristics like reverberation time, early decay time, later decay time and speech intelligibility.

How to measure room impulse response? Here is how, with a software called Aliki (free and open source).

Impulse response of semi-anechoic room in VibrasticLab


In Ubuntu, it is easy to install Aliki using apt-get:
sudo apt-get install aliki
It will install Aliki (gui) and its dependencies.

Step-by-step :

  1. Session, load your session or make new folder. If you didn't choose session, current working directory is used to store data (/home).
  2. Generate sweep,  Leave configuration by default, use 48000 of sampling rate, and give it a name (for example sweep48.ald), it will be stored in your session sweep/sweep48.ald
  3. Capture, Set your input microphone (remove unused, use one channel) and give it output name (e.g: sweepResponse). Set the output channel and the sweep file generated in previous steps.
  4. Load >> Convol. Load your saved sweep response, it is saved in capture model. Then choose sweep file to convolve with. Click Apply.
  5. Save session. Save your deconvoled file (in previous step) and cancel to exit from Convol session.
  6. Load your saved impulse response, it is stored in your session impresp directory.  
  7. Export, to .wav file. Choose Export, Use the following configuration: single channel wav file, all channel, 16 bit, all session in one file.
  8. Your exported wav file is saved in your session (if set), or in your current directory (if session not set).
Aliki UI to measure impulse response
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