## 3 Results  
### Describing the Discrimination Ability of the Program  
According to the signal detection theory [24], measures of performance in the discrimination test are called sensitivity measures: High sensitivity refers to good ability to discriminate while low sensitivity corresponds to poor ability. In this work, the purpose of the Yes-No experiment is to evaluate the program's sensitivity to the spectral irregularities below 200 Hz.  
The Yes-No experiment concerns two kinds of stimulus and two possible responses, leading to four possible types of events, as shown in Table 2. These four events are conventionally termed as Hit, Miss, False alarm, and Correct rejection in the detection theory [24]. Correctly recognizing an equalized test signal is termed a Hit while failing to recognize it is called a Miss. Mistakenly identifying an unprocessed test signal as equalized is termed a False alarm while correctly responding \"unprocessed\" is a Correct rejection. High sensitivity is indicated by a concentration of trials counted in the upper left and lower right of the table, that is, more Hits and more Correct rejections.  
For each program, the number of trials of each type was tabulated in Table 2. It could be found that, in this experimental design, the sum of each row was a constant, which is 132 (11 subjects \(\times\) 6 trials \(\times\) 2 observations). Hence, of the four numbers of trials of each type in the table, only two provided independent information about the program's performance. By dividing each number by the sum of the row, two independent variables were obtained to summarize the table: EQ Score (EQ stands for Equalized) and Flat Score. The EQ Score was the proportion of Equalized trials to which the subject responded \"A and B are different. (indicating that the test signal is equalized)\", and the Flat Score was the proportion of Unprocessed trials to which the subject responded \"A and B are the same.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Test Signal** & **Response** & **A and B are Different.** & **A and B are the Same.** \\  & **(Equalized)** & **(Unprocessed)** \\ \hline Equalized & Hit (EQ Score) & Miss \\ Unprocessed & False alarm & Correct rejection (Flat Score) \\ \hline \hline \end{tabular} Note. EQ Score is the ratio between the number of Hit trials and the total number of trials where the test signal is equalized. Flat Score represents the ratio between the number of Correct rejection trials and the total number of trials where the test signal is unprocessed.  
\end{table}
Table 2: Four types of events in the Yes-No experiment.  
(indicating that the test signal is unprocessed)\". By definition, a higher EQ Score and a higher Flat Score are related to a better discrimination ability of the program.  
The EQ Score and Flat Score were calculated for each program to describe the discrimination ability of the program. In addition, the times when the program mentioned was difficult or easy to complete the test in the post-test questionnaire were measured for each program, and then normalized to its upper limit, i.e., 22 (11 subjects \(\times\) 2 observations), in order to describe the listeners' subjectively perceived difficulty of the program when conducting the test.