| dc.description.abstract | This project was done in two parts. The first part was to investigate the behaviour
of a small jet placed in five different positions between the antinode and the node
in an acoustic field. This jet was measured with a hotwire at the jet exit and
two microphones inside the jet. The velocity amplitudes from the hotwire and the
pressure amplitudes from the microphones were plotted against each other for all
five positions. This showed that the size of the pressure amplitudes inside the jet
was linear to the velocity amplitudes at the exit, and that the gradient was the
same for all positions. The strongest amplitudes were at the antinode and the
weakest at the node. The different amplitudes for the five positions were compared
to the theory of an acoustic field inside a box, and compared well, indicating that
the measurements were done correctly.
The second part was a larger jet that was acoustically forced with the node placed
at the centre of the jet. Eight microphones were mounted flush around the jet
with 45between them, right beneath the jet exit. The pressure inside the jet was
measured with these eight microphones for two different resonance frequencies.
This was done to see how the steepness of the gradient affected the measurements.
The results from the highest resonance frequency compared well with theory, but
the results from the lower did not. All the signals from the lowest resonance
frequency had a phase shift. This was investigated, and it concluded with that the
amplitudes from the speakers were different. | |
