# Acoustic Impulsive Noise Based on Non-Gaussian Models: An Experimental Evaluation
## 4 Experimental Results and Analysis
### Scenarios Analysis  
Our first scenario is a silent auditorium illustrated in Figure 2. It is an environment with low-level noise, consequently presenting a high-quality audio signal.  
We labeled this environment as the **Indoor Scenario**. It is an auditorium acoustically isolated without external audio noise. This environment represents a place for conferences, presentations, with a low level of noise. The measured signal is shown in Figure 3 when there is no audio source. The signal does not present impulsiveness.  
Figure 1: Experimental measurement setup.  
Figure 2: Indoor Scenario: Auditorium acoustically isolated without external audio noise.  
The second measurement in indoor scenario is accomplished when a speech signal source is present, and the person intentionally made small moves before speaking. The measured signal exhibits a hardly ever impulsive noise (because of the person's moving), as shown in Figure 4. This is evidence of the independence between noise and audio source as well as the low impulsiveness of noise in this scenario (low noise power compare to the signal power).  
We labeled the second environment as the **Hall Scenario**. It is a scenario noisier than the indoor, represented in Figure 5. Its mixed indoor/outdoor configuration is composed of two windows and two doors, allowing audio noise from wind. The measures were performed at night in the absence of noise from equipment as a Heating, ventilation, and Air Conditioning.  
Figure 6 presents the measured signal in the hall scenario, making evidence an infrequent impulsive noise, probably from some external source.  
Figure 4: Signal behavior in the indoor scenario with a person moving and speaking.  
Figure 3: Signal behavior in the indoor scenario without audio source.  
Figure 7 shows the signal when a person's speech is present. As previously discussed in the indoor scenario, the independence between noise and audio source is observed, but now we see impulsiveness of noise due to some external source. However, this scenario has still low noise power compare to the signal power.  
The third environment, named **Outdoor Scenario**, is illustrated in Figure 8. It is the noisiest one, with audio noise coming from the outside environment (building, traffic and crowd noise).  
Figure 5: Hall Scenario: A mixed indoor/outdoor environment at auditorium hall.  
Figure 6: Signal behavior in the hall scenario without audio source.  
Figure 7: Signal behavior in the hall scenario with a person moving and speaking.  
Figures 9 and 10 present the signal in the outdoor environment without audio source and with a person's speech, respectively. A careful observation of the signal behavior suggests that it does not have a constant second-order moment (its variance is time-dependent). This could happen as a consequence of different origins of noise, such as traffic, unknown speakers, crowds, wind, and human-made. We claim there is more impulsiveness if different noises sources are present.  
Figure 8: Outdoor scenario: Outside the auditorium with noise coming from the outside environment.  
Figure 10: Signal behavior in the outdoor scenario with a person moving and speaking.  
Figure 9: Signal behavior in the outdoor scenario without audio source.