*3.2. Data Processing*

On the one hand, environment recognition comprehends the use of the microphone with the application of the Fast Fourier Transform (FFT) [61] to extract the relevant features. After the application of the FFT, several features were extracted, including 26 MFCC coefficients and standard deviation, average, maximum value, minimum value, variance and median of the raw signal.

On the other hand, the recognition of the standing activities makes use of the environment recognized and accelerometer, magnetometer and/or gyroscope sensors' data with the application of a low pass filter [62], extracting the same features presented in Reference [4].

## *3.3. Data Fusion*

This module encompasses several databases obtained from the combination of different sensors, and features, which are depicted in Figure 1. The different combinations of sensors are:


**Figure 1.** Different combinations of features for the recognition of environment and standing activities.
