An electret microphone was used to record the startling tone burst as a reference. All skin conductivity data was sampled and saved at 16 samples per second with 0.01 micro-Siemens resolution. An example of data collected from the multiple startle experiment. The shoe provides a convenient location for sensor placement. Here, a skin conductivity sensor is placed in the arch of the shoe and a pressure sensitive resistor is placed on the heel.
Sensors look unobtrusive when worn.
The similarity between skin conductivity readings measured from the palm of the hand and the arch of the foot offers the possibility of placing sensors in the wearer's shoe instead of on the hand. The startle experiment was designed to test the correlation of the hand and foot responses under extreme audio stimuli. The correlation coefficient was used to measure similarity between the signals taken from the three locations. The results of these correlations are reported in Table 2. In the natural sciences, the correlation coefficient is used in the Pearson correlation to test significance of traits, based on the number of data points.