## 5 Quality Evaluation Study  
This quality study, considering simulcasted DAB+ and FM radio programs, was performed on a representative group of 45 individuals. It should be mentioned that currently six services are available both in digital and analog terrestrial radio. However,  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**No.** & **Profile** & **Codec** & \
\begin{tabular}{c} **Bitrate (kbps)** \\ **Previous** \\ \end{tabular} &
\begin{tabular}{c} **Bitrate (kbps)** \\ **Current** \\ \end{tabular} \\ \hline
1 & Talk 1 & AAC-LC & 112 & 112 \\
2 & Arts & AAC-LC & 128 & 128 \\
3 & Talk 2 & AAC-LC & 112 & 112 \\
4 & Pop Music & AAC-LC & 112 & 128 \\
5 & Informative EN & AAC-LC & 64 & 64 \\
6 & Informative PL & HE-AAC v1 & 64 & 64 \\
7 & Classical Music & AAC-LC & 128 & 128 \\
8 & Children & HE-AAC v1 & 72 & 72 \\
9 & Regional PL & AAC-LC & 104 & 112 \\
10 & Regional EN & HE-AAC v1 & - & 72 \\
11 & Data & - & 16 & 16 \\
12 & Journaline & - & 16 & 16 \\ \hline \hline \end{tabular}
\end{table}
Table 6: Evaluated DAB+ multiplex ensemble.  
the reception quality of the Informative PL program, recently introduced to FM radio, was not always stable. That is why it was omitted from the study.  
The subjective judgement of five simulcasted radio programs, available at stable reception conditions, was realized according to [50; 51; 52]. Is should be clearly stated that the quality assessment was performed in an indoor environment with a high-quality radio receiver and headphones.  
First, listeners were asked to rate the overall quality of each real-time DAB+ transmitted radio program over a period of approximately 10-20 s, separated by a 5 s interval, in a five-step MOS ACR (Absolute Category Rating) scale with no reference signal available from one (bad quality) to five (excellent quality). Next, this examination was performed for real-time FM broadcasted programs. Similarly as in case of DAB+, each radio program was presented over a period of approximately 10-20 s, separated by a 5-s interval. As previously, listeners were also asked to provide a score representing the overall quality in a five-step MOS scale, with no reference signal. In both cases, that is, FM and DAB+ signal quality evaluation, participants were not informed about the name nor profile and neither bitrate (in case of DAB+) of the currently assessed broadcast. Radio programs were presented in a randomized manner and labelled as Program 1-5. The results considering the quality of simulcasted DAB+ and FM radio programs are shown in Figure 1.  
According to obtained results, all scores favor the digital system. The observed difference ranges from 0.02 (Arts--broadcasted in DAB+ at 128 kbps) and 0.05 (Pop Music--broadcasted in DAB+ at 128 kbps) to 0.77 (Regional PL--broadcasted in DAB+ at 112 kbps). Moreover, a comparison has been performed by considering the results published in 2017 [25], including the same group of radio programs as well as the same number of individuals, namely 45, participating in the listening study. The results are shown in Figure 2.  
As shown, the scores are quite similar, with differences ranging from 0.04 (Pop Music--bitrate changed from 112 to 128 kbps) to 0.52 (Talk 2--unchanged bitrate of 112 kbps).  
It is worth mentioning that no participants had hearing disorders. Furthermore, in order to acquaint each person with the listening equipment and the purpose of the test, every individual took a training phase before starting the essential study. Of course, no one was informed about the actual bitrate of the currently assessed radio program. In the case of both DAB+ and FM, broadcasts were only labeled as Programs 1 to 5 in a randomized manner.  
Figure 1: Subjective quality evaluation of simulcasted radio programs.