**3.1.1 Step 1: Band approximation of formants location**

The first step consists of a rough analysis of the signal's wavelet packets tree. In order to locate formants frequencies, the energy of each subband is analyzed. The maxima of this energy signal determine formants location. The scheme of the process is shown in Figure 1.

Firstly, the wavelet packets tree is calculated up to the desire level, the chosen level is calculated taking into account the sampling frequency and the resolution required.

After having obtained the wavelet packets, the energy of each last level node is calculated. The Energy is stored in an array and its envelope is estimated. This envelope smoothes the energy signal and thus, the maxima can be easily calculated.

Oesophageal Speech's Formants Measurement Using Wavelet Transform 87

The main advantage of this method is that it is possible to save a lot of computational load but preserving a high accuracy level at the same time. For example, if an 8 level basic tree is to be taken and its formantic nodes are expanded two levels, it is possible to obtain a 10

Using the advantages of the previously described algorithms, authors have developed a tool

level resolution by consuming an 8 level computational load.

called "PAS Voice". The welcome screen will then be displayed:

Once the application has been started up, the main screen will be displayed:

**3.2 User interface** 

Fig. 2. Welcome Screen

Fig. 3. Main Screen

Fig. 1. Adjustable Resolution Analysis Schema
