Table of Contents

Hardware

Software Installation

The measurement software is called zProbe. It is a custom software written in the Python language. It is installed on the CAML laptop in C:\Users\caml\Documents\zProbe\. To execute ZProbe, you have to run […]ZProbe\src\main.py.

This software uses PyQt4 for the GUI and SciPy for the calculations. On windows, the Python(x,y) (www.pythonxy.com/) package contains these dependencies and more. It is the recommended way to install python.

The audio i/o operations are done using the PyRtAudio package. This is a python external written in C++. It is located in C:\Users\caml\Documents\rtaudio-4.0.8\contrib\python\pyrtaudio. In order to compile and install this library, the Microsoft Visual C++ Express Edition must be installed and configured properly. This has been done on the CAML laptop. You can build and install this external by executing: python setup.py install

The driver of the audio card must be installed properly.

Hardware connections

  1. The 6 microphones should be connected in order, the first one being located near the measurement plane. The PCB Piezotronics preamp has lights that indicate if each of the microphone is connected. They can be used to determine which channel each cable is connected to.
  2. The outputs of the PCB preamp are connected to the RME Fireface 800 using BNC-to-quarter-inch cables.
  3. The RME Fireface is connected to the computer with a Firewire cable.
  4. The first output channel of the RME card is connected to the amplifier using a quarter-inch-to-quarter-inch cable.
  5. The amplifier speaker out is connected to the horn driver.

Operation

Before starting a new measurement session, you must create a new data directory with the menu item Measurements/New Directory.

Then, you perform the calibration with Measurements/New Calibration. A new dialog appears which let you measure the three calibration objects. There is a plot that lets you inspect the impulse responses. The calibration data is saved in the currently selected directory and is used for all subsequent measurements saved to this directory.

Then, you can measure your objects with Measurements/New Measurement.

Notes

The volume knob of the amplifier should be set to a fairly low value. If it is too loud, there will be distortion. If it is too low, the S/N ratio will be adversely affected.

Software

The software can still be improved in various ways. The python sources can be edited directly. There is no need to compile or install anything … just rerun the python source after editing.