## 3 Listening Test 1
### Stimuli, Subjects and Test Methods
Around this particular frequency, vacuum cleaner noise decreases, and this decrease is different for different vacuum cleaners. Three different parametric low-pass filters with three different Q values were used, so the slope of each line in the FFT was different. Therefore, it was possible to obtain vacuum cleaner noise with different high-frequency components and thus different sharpness values. Since changing the high-frequency content affects the overall loudness of the sound, the overall level is slightly shifted for each filter case. As a result, the same loudness values are obtained. One example is shown in Figure 15. Here, three stimuli have the same loudness but different sharpness values. To generate the stimuli in this listening experiment, one original stimulus was taken as the basis. This original sound was selected such that the signal had no tonal components, a loudness of 20 sone (ISO 532-1) and a sharpness of 3.13 acum (Aures). Both loudness and sharpness values lie in the middle of the observed loudness and sharpness ranges. Intentionally, a stimulus without a tonal component was selected to eliminate any possible bias originating from the tonal component in this listening experiment. Three different test methodologies were compared for factorial design experiments 1, 2 and 3 (Figure 16). For these three experiments, the slider scale, magnitude estimation and random access methods were used. The slider scale experiment (Figure 16, part a) used a quasi-continuous rating slider with verbal anchors (from 0 to 100 with a step size of 1) with equidistant neighboring categories (not at all, slightly, moderately, very or extremely), as in listening test 1. Participants used this slider to rate the annoyance of the given stimuli. The appearance of the stimuli was randomized for each participant, and participants were not allowed to navigate back and to change their evaluations for previous stimuli. In the magnitude estimation experiments (Figure 16, part b), an anchor stimulus and a defined annoyance value for that particular anchor stimulus were used. Participants were then asked to rate the annoyance of a particular stimulus relative to the anchor stimulus. The reference value for annoyance was set to 100 for the anchor stimulus. Participants could listen to the two given sounds as many times as necessary and they gave their ratings by entering a number in the free space below the play button. The order of the stimuli was also random, as in the slider scale experiment. This random order was different for each participant, and participants could not go back and change their ratings. Lastly, the random access method (Figure 16, part c) used a user interface where all of the stimuli were presented to the participant simultaneously. At any time, the participant could click the play buttons in any order to listen the stimuli, could compare them in pairs and could change their previously established response. They could drag and drop the playback icons to the field, which contained the same verbal anchors as in slider scale experiment. The position of the playback icon (i.e., stimulus) on the y-axis was taken as the rating of a participant. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multicolumn{4}{c}{**The 5 \(\times\) 3 and 3 \(\times\) 3 Factorial Designs on Loudness and Sharpness**} \\ \hline Stimulus \# & Experiment Design & Loudness (some) & Sharpness (acum) \\
1 & \(5\times 3\) & 13.1 & 2.4 \\
2 & \(5\times 3\) & 13.3 & 2.97 \\
3 & \(5\times 3\) & 13.4 & 3.47 \\ \hline
4 & \(3\times 3\) \& \(5\times 3\) & 16.4 & 2.42  
The main difference between the random access method and the slider scale method is that, in the random access method, participants can always replay all stimuli, can change their decisions and have a better sense of control over their evaluations. However, the number of stimuli in such experiments is rather limited.