Figure 4.

BMU activation trajectories of the SOM (A,C) and BMU activation sequences (B,D) for randomly selected sound samples from classes “bell5” (Row 1), “bottle1” (Row 2) and “buzzer” (Row 3) of a trained 12 × 12 SOM on the RWCP dataset. For BMU activation trajectories, the lines connect activated BMUs from frame to frame. The activated BMUs are highlighted from light to dark over time. For BMU activation sequences, the neurons of the SOM are enumerated along the y-axis and color matched with neurons in the BMU activation trajectories. The low intra-class variability and high inter-class variability for the BMU activation trajectories and sequences are observed.