audibilityofechoes,binaural

The same sound files as the previous task were created here but we added the direction by adding a HRIR to the direct sound and the reflection. We used two different sorts of HRIR, one from a real person (Itakura) and one from the dummy head (CIPIC).

For each measurement, the direct sound has been convolved with a HRIR for 0 degree, and the reflection has been convolved with two different HRIR's (45 degrees and 90 degrees).

These sounds were created with a delay time of 0.1 and a reflection level of 0.3 (almost -9 dB compared to the direct sound). This level enables us to hear properly the reflection but less loud than the direct sound.

45° - 90°

Once again the speech is the best sound for the listener to notice changes e.g. the direction of reflection.

One could also notice, if hearing closely, that there is a little level difference between the reflection at 90° and the reflection at 45°, but more obvious is the change in timber (coloration). It seems that the 90° reflection has less coloration than the 45° reflection. That proves a higher sensitivity at 45° than at 90°.

In order to discuss the results in comparison with the ATA figure 5.4 below, measurements have been performed with a delay time of 50ms. One can once again clearly see that the sensitivity is higher for 45° of incidence of the reflection, than for 90° of incidence. But if one now wants to compare the effect of the delay time, one could say that the sensitivity increases with the delay time, indeed one could, in a easier way, determine the origin of the incidence of the reflection with a longer delay time.

Speech - Drums - Orchestra

While one could easily perceive the incidence of the reflection for a speech or drums, it is very difficult to do the same with orchestral music. Since this one is made out of several "sources", several "direction of incidence" are involved. That is why it is so difficult to hear the direction of incidence of the reflection. On the other hand it is really clear that a sort of coloration occurs when adding reflection with a direction of incidence, since one can clearly hear a difference in timber.

Real person - Dummy head

Finally one could try to detect differences in the two different types of HRIRs. The main difference between those two created sounds is that the reverberation is higher with the HRIR real person than with the dummy head.