# Sound Synthesis of Objects Swinging through Air Using Physical Models +
## 5 Evaluations and Results
### Subjective Evaluation
#### 5.1.1 Listening Tests  
A double-blind listening test was carried out to evaluate the effectiveness of our synthesis model. The Web Audio Evaluation Tool [27] was used to build and run listening tests in the browser. This allowed test page order and samples on each page to be randomised. All samples were loudness normalised in accordance with [28]. Headphones were used to administer the sounds to participants. These were either AKG K553 Pro Closed-Back Studio Headphones or Beyerdynamic DT150 closed back Isolating Studio Headphones. Each participant was presented with five test pages, one for each of the preset sound effects. The wooden sword, baseball bat, golf club and broom handle pages contained two real samples, two samples from our physical model (PM), two samples generated by spectral modelling synthesis (SMS) [29] from a recording and an anchor. The metal sword page included two real samples, one synthesis sample from [4], one synthesis sample from [6], one SMS sample, one sample from our physical model and a sample from the physical model with cavity tone compact sound sources added. All the sampled recordings were captured by the authors within the Listening Room, Electronic Engineering and Computer Science Department, Queen Mary University of London. They were recorded on a Neumann U87 microphone placed approximately 20 cm from the midpoint of the swing and at 90 degrees to the plane of the swing. The impulse response of the room was captured and applied to all other sounds in the listening test so that the natural reverb of the room would not influence the results (except samples from [4; 6]). The anchors were created from a real-time browser-based synthesis effect ([http://c4 dm.eecs.qmul.ac.uk/audioengineering/RTSFX/app/main-panel/whoosh.html](http://c4 dm.eecs.qmul.ac.uk/audioengineering/RTSFX/app/main-panel/whoosh.html)), to allow a thorough comparison of how plausible the synthesis method is compared to the recorded sample. It was expected that a low pass filtered sample, as used in the MUltiple Stimuli with Hidden Reference and Anchor (MUSHRA) standard, would still be considered plausible, whereas a low-quality anchor would encourage the full use of the scale and allow for better understanding as to the effectiveness of the synthesis method. Rating the plausibility of sound from a physical model was the preferred judgement in [30], stating a plausible sound as one that listeners thought \"was produced in some physical manner\". Box plots for all five objects are shown in Figure 3. Our physical model outperforms the alternative synthesis methods on all of the objects except the metal sword. The metal sword performed poorly for plausibility in this test, with the model with added cavity tones performing slightly better. Figure 3: _Cont_. \begin{table}
\begin{tabular}{l c c c c c c c} \hline \hline  & **Anchor** & **SMS1** & **SMS2** & **PM1** & **PM2** & **Real1** & **Real2** \\ \hline ANCH &. & *** & *** & *** & *** & *** & *** & *** \\ SMS1 & &. & - & *** & *** & *** & * \\ SMS2 & & &. & *** & *** & *** & *** \\ PM1 & & &. & - & - & - \\ PM2 & & & & & - & - \\ Real1 & & & & & & - \\ Real2 & & & & & & - \\ \hline \hline \end{tabular}
\end{table} 
Table 6: The effect of different samples for a golf club (**** \(\Rightarrow\)\(p\) < 0.0001, **** \(\Rightarrow\)\(p\) < 0.001, **** \(\Rightarrow\)\(p\) < 0.01, **** \(\Rightarrow\)\(p\) < 0.01, **** \(\Rightarrow\)\(p\) < 0.05, - \(\Rightarrow\)\(p\)\(\geq\) 0.05). SMS, spectral modelling synthesis; PM, physical model; Real, recorded sample. \begin{table}
\begin{tabular}{l c c c c c c} \hline \hline  & **Anchor** & **SMS1** & **SMS2** & **PM1** & **PM2** & **Real1** & **Real2** \\ \hline ANCH &. & - & * & *** & *** & *** & *** \\ SMS1 & &. & - & *** & *** & *** & ** \\ SMS2 & & &. & *** & *** & *** & ** \\ PM1 & & &. & - & - & * \\ PM2 & & & & &. & - & * \\ Real1 & & & & & &. & - \\ Real2 & & & & & &. & \\ \hline \hline \end{tabular}
\end{table}