Correction to: Personal and Ubiquitous Computing

https://doi.org/10.1007/s00779-020-01402-6

The actual Fig. 13 has been missing and in place of Fig. 13, Fig. 14 has been shown.

Fig. 13
figure 1

Illustration of signature of ultrasonic and sound sensor from four sensor grids for a lecture scenario

Fig. 14
figure 2

Illustration of experimental results of lecture scenario

The correct figures are shown on the next page.

The original article has been revised.