As mentioned previously, I will be conducting listening tests with the public, in an attempt to answer the question of whether individualised HRTFs improve localisation over generic ones, in a binaural environment.
The tests are a continuation of work undertaken at the University of York regarding a comparison of localisation performance in 1st, 3rd and 5th order Ambisonics, available here, and so will involve similar test conditions. The participant is played pink noise bursts over a virtual speaker array (via headphones) and uses a 3DConnexion ‘Space Mouse’ to pan a moveable, ‘active’ source with a stationary, ‘reference’ source to match the two. When the user is satisfied that they are both in the same position their position is logged and the process is repeated for new reference source.
(3DConnexion Space Mouse, which enables the user to pan left/right as well as up/down, giving complete freedom to move a point around the surface of a sphere)
The virtual speaker arrays will be randomised so participants won’t know whether they are using their own HRTFs or other generic ones, such as those from the KEMAR database. Furthermore, we will be randomising between 1st, 3rd and 5th order Ambisonics, to test the comparison of HRTFs more rigorously
The test will be conducted in the same space that the participants’ HRTFs were captured, in this case the speaker array at the University. By taking these measurements in a non-anechoic environment, we are not only capturing the head’s transfer function but also the room’s, as sound is reflected off of the various, albeit absorbent, surfaces. If done correctly, the user, whilst positioned in the rig and wearing headphones, should be unable to tell whether sounds are played out of the real loudspeakers or their headphones (with their own HRTFs loaded).
Additionally, the test will be performed under head-tracking conditions, meaning that the virtual speaker array will have to pan in real-time as the user turns their head.
After the tests are concluded the results should be able to give a clear indication of which type of HRTFs should be used for a particular order Ambisonics.