# Wearable Voice Dosimetry System
## 3 Materials and Methods
### System Validation
#### 3.4.2 Validation of the Parameters of Interest in the Human Voice  
To validate the results obtained by the device regarding the parameters of the voice we are studying (\(F_{0}\), relative intensity, and phonation time), the device was placed on three subjects (two men and one woman) and recordings were made with the device and, simultaneously, with the audio recording and sound level measurement equipment at the Voice Laboratory of the Clinica Universidad de Navarra. 1. [wide=0.5 cm]
2. Validation of \(F_{0}\) estimation:  
For the validation of the \(F_{0}\) measurement, the device was placed on each of the subjects. Those subjects generated a tone scale, each within their comfortable range and without predetermining the frequency of each of the tone steps. Each of the tones, produced as a vowel, was kept constant for 1 to 3 s with a brief silence in between. The \(F_{0}\) measurement was performed using the proposed system and a microphone connected to a PC through the A/D SoundScope/16 card and analysed with SoundScope 1.2 software. For each total step, the result obtained from SoundScope measurements is a frequency value that corresponds to the mean \(F_{0}\) measured by the program during that step. Subsequently, both recordings were analysed using the correlation statistic to determine the absolute error of the measurements performed by the device with SoundScope measurements as the reference. Figure 7 shows the 2508 data collected by the device in the 38 tonal steps. The first 29 steps correspond to subject 1 and were taken in 2 measurements of 21 and 8 tonal steps, respectively. The next four tonal steps correspond to subject 2 and the last five to subject 3. The SoundScope measurements have the form of steps with a constant value of \(F_{0}\) during the tonal step. This is because SoundScope only produces one frequency  
The relative intensity measurements from the device were compared with the intensity measurements recorded by the sound level meters: ISO-TECH SLM-1352A, (RS Integrated Supply, Birchwood, Warrington WA2 6 UT, UK) and LingWAVES SPL (WEVOSYS medical technology GmbH, Bamberg 96052, Germany) meter. Again, the three subjects produced tones of increasing intensity within their range of comfort. Each of the tones was kept at constant intensity for 1 to 3 s with a brief silence in between. Subsequently, the statistical comparison of the obtained data was performed. For the validation of the relative intensity, measurements of constant intensity of subject 1 were taken. During the recording, the sound level meter produced 77 values, while the device produced 5190 values. In the case of subject 2, these were 8 and 646 measurements, respectively. The measurements for subject 3 were discarded because she did not perform the vocal exercise correctly, i.e., vowels were not kept at constant intensity. The results are shown in Figure 10. A very high linear correlation is observed for both subjects. These results show the robustness of the device as the measurements with subject 1 were made over several days, including taking off and putting on the device, with the possible small variation in pendant tension. 3. Phonation time validation:  
The phonation time measured by the device was compared with that recorded using the YETI PRO microphone and the Sound Forge 10.0 software. During the experiment, each of the three subjects performed a monologue for 2-3 min. The microphone recording was analysed using Audacity 2.3.1 software. Since the device stores data in microSD memory every 120 s, the first 100 s of the monologue were used for comparison. All pauses in the audio recording were eliminated. The duration of the remaining recording is the phonation time. With this, an audio signal is obtained that concatenates all the voice fragments recorded by the microphone. The number of subsegments in the device recording that show a non-zero \(F_{0}\) during the first 100 s of the recording is multiplied by the segment duration (31.25 ms) to obtain the total time that has been considered phonation speech.