## 2 Stimuli--Signal Characteristics of Vacuum Cleaners
### Signal Characteristics
Eventually, three different sharpness values were calculated: the first one is Aures sharpness, with the loudness values calculated according to ISO 532-1; the second one is the Bismack sharpness, with the loudness values calculated according to ISO 532-1; and the last one is DIN 45692 sharpness, with the loudness values calculated according to DIN 45631. Finally, single value tonality values were calculated based on the publications of [PERSON] and [PERSON] [25; 28] and on the hearing model of [PERSON] [29]. Both models have a psychoacoustic basis, but there are also clear differences. The [PERSON] model starts from Zwicker loudness and extracts the tonal components from a FFT spectrum. The degree of tonality is calculated based on the ratio of tonal to non-tonal loudness as a function of time. Spectral information is not included in this model [30]. On the other hand, the [PERSON] model includes a hearing model approach in which the signal is first filtered through the outer and middle ear filtering and the partial loudness of tonal to non-tonal content in critical bands is calculated to determine the tonal loudness. In addition, recent studies have found [31; 32; 33; 34; 35; 36; 37; 38] that the perception of tonal content is frequency-dependent, so the final decision on the strength of the tonal content takes into account the frequency of the tone. Additionally, the distribution of the aforementioned psychoacoustical parameters over 15 vacuum cleaners can be found in Figures 4-6. From the calculated values, it can be observed that the variations over loudness and sharpness show a fine distribution over the defined range. The tonality values also show a degree of distribution for tuHMS values between 0 and 1.3, with one outlier with strong tonality. The frequency content of the emitted noise strongly depends on the positioning of the vacuum cleaner (hard flooring or carpet). Since it absorbs some of the emitted energy in the mid- to high-frequency range, the carpet condition changes the noise. To illustrate this effect, Figure 7 shows the spectra of all recorded vacuum cleaners with and without a carpet. The left panel shows the spectra for the recordings without a carpet, and the right panel shows those with a carpet. The figure colors were intentionally kept in greyscale so that the differences between the hard flooring and carpet cases could be easily compared. In this figure, it can be seen that the levels can be lowered by up to 10 dB in the regions above 500 Hz. This shows that the variation in the recordings and stimuli pool can be \begin{table}
\begin{tabular}{l l c c c} \hline \hline
**Case** & **Parameter** & **Min** & **Max** & **Unit** \\ \hline \multirow{8}{*}{Hard Flooring} & Level & 64.3 & 76.7 & dB \\  & A-weighted level & 61.4 & 76.4 & dB(A) \\  & Loudness (ISO 532) & 15.5 & 38.5 & some \\  & Sharpness (DIN 45631 and ISO 532 + Aures) & 2.82 & 4.5 & acum \\  & Sharpness (DIN 45692 \(-\) DIN 45631) & 1.76 & 2.15 & acum \\  & Sharpness (DIN 45631 and ISO 532 + Bismack) & 1.62 & 1.95 & acum \\  & Tonality (Aures) & 0.0505 & 0.2470 & tu \\  & Tonality (Hearing Model) & 0.06 & 2.51 & tuHMS \\ \hline \hline \multirow{8}{*}{Carpet} & Level & 59.7 & 76.1 & dB \\  & A-weighted level & 52.1 & 75.4 & dB(A) \\ \cline{1-1}  & Loudness (ISO 532) & 8.6 & 36.4 & some \\ \cline{1-1}  & Sharpness (DIN 45631 and ISO 532 + Aures) & 2.47 & 4.43 & acum \\ \cline{1-1}  & Sharpness (DIN 45692 \(-\) DIN 45631) & 1.63 & 2.15 & acum \\ \cline{1-1}  & Sharpness (DIN 45631 and ISO 532 + Bismack) & 1.5 & 1.97 & acum \\ \cline{1-1}  & Tonality (Aures) & 0.0598 & 0.3230 & tu \\ \cline{1-1}  & Tonality (Hearing Model) & 0.05 & 1.95 & tuHMS \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Calculated minimum and maximum acoustic and psychoacoustic measures among different vacuum cleaners for the hard flooring and carpet cases.