The IRs have been edited and analysed for a long time after the measurements in an attempt to understand and eliminate the additional peaks. However, these peaks were affecting the frequency spectrum significantly, making the experiment inaccurate when comparing them to the theoretical IRs. As a result the experimental procedure had to be repeated.
The anechoic chamber was booked for 2 consecutive days on Monday the 19th and Tuesday the 20th of August. Even though this was only two weeks away from the deadline of the project, it was the only time available. To save time, the required MATLAB scripts were created in advance using the IRs from the previous measurements. This would speed up significantly their analysis stage.
The experimental procedure was repeated. After setting everything up just like last time, the measurements took place for a single side of a the trunk and then analysed. The same unwanted peak was still present in the IRs. This suggested that there was an unwanted reflection within the system. After examining multiple potential surfaces, using trigonometry, and by repeating measurements. It appeared that the reflection was most likely caused by the net on the floor of the chamber. The measurements were repeated after placing foam on the floor. The unwanted peak was significantly eliminated. The measurements were repeated once again from the beginning.
Figure: Place foam on the floor of the Anechoic Chamber to eliminate the unwanted reflections in small angles.
George Sarantinos 