8.6 Too many localization results / no localization results

Problem

• Localization with the LocalizeMUSIC node is not performed well.

• Despite the absence of sounds, sound sources are continuously localized from a specific direction.

• You wish to set an appropriate value for the THRESH property of the SourceTracker node.

Solution

1. Execute the network file for which the DEBUG property of the LocalizeMUSIC node is set to true.

2. Watch the power values of a MUSIC spectrum when there are no sounds and when there are sounds such as clapping.

3. Set the power value to an intermediate between these two.

The power should be set slightly higher than the steady power in the presence of silence. For example, if the steady power is around $25.5 – 25.8$, set THRESH at $26$ . In step 1, visualizing the time-direction MUSIC spectrum like a spectrogram facilitates the choice of threshold.

Discussion

Since the values output by the LocalizeMUSIC node are dependent on the gains of the microphones and the surrounding environments, appropriate values should be set by trial and error, as above. The following trade-off relationship arises in the setting of THRESH: When THRESH is set at a small value, localization can be performed for small power sources, allowing localization of unexpected noises (e.g. footsteps). When THRESH is set at a high value, loud sounds are not localized, whereas greater power is needed to localize uttered sounds.