## 3 SADIE II Binaural Database  
### Data Summary  
In order to assess the perceptual quality of individual and non-individual HRTFs, a database of individual measurements was required. To benefit future work and to be compatible with popular binaural renderers, spatially regular Ambisonic configurations were prioritised. Ambisonics has proven to be a popular workflow for binaural rendering [37; 38] and as such it is favourable to contribute data to the field. Although not pertinent to this study, BRIRs are also presented in this paper for completeness.  
Alternative human HRTF databases suffer from a lack of measurements made at low elevations and a limited overall resolution (see Table 2).  
Measurements of dummy heads are more readily available [43; 44], however, are of course by nature less applicable to individual HRTF experimentation. The SADIE II Database includes measurements down to an elevation of \(-81^{\circ}\) and provides a minimum of 2114 measurements for each human subject.  
The following measurements were taken of 31 subjects (22 male, 5 female, 2 non-binary, 2 dummy mannequins, ages: 20-63 (majority 20-30)) with normal hearing:  
* HRTFs of a fixed latitude-longitude distribution [45],
* HRTFs of 14 key Ambisonic loudspeaker configurations (listed in Section 3.2.1),
* BRIRs of a 50 point Lebedev Grid [46],
* Headphone IR of Beyerdynamic DT990s (+ Headphone EQ filter).  
In the case of the KU100 and KEMAR mannequins, recordings were made using their built in microphones. For human subjects, a pair of Knowles FG-23329-C05 microphones (Knowles Electronics. Itasca, IL, USA.) were used and a blocked meatus approach was taken [4]. The microphones were mounted inside 3D printed capsules and secured in the participants' ears with silicon putty (see Figure 1).  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Database** & **Number of Points** & **Minimum Elevation** \\ \hline
**SADIE II** & 2818/2114 & \(-81^{\circ}\) \\
**ARI [39]** & 1550 & \(-30^{\circ}\) \\
**CIPIC [40]** & 1250 & \(-45^{\circ}\) \\
**LISTEN [41]** & 187 & \(-45^{\circ}\) \\
**SADIE [18]** & 170 & \(-75^{\circ}\) \\
**FIU DSP Lab [42]** & 72 & \(-36^{\circ}\) \\ \hline \hline \end{tabular}
\end{table}
Table 2: A comparison of the number of points and minimum elevations measured by a number of popular human HRTF databases.  
Once inserted, the microphones were not removed or re-positioned until all audiological measurements had been completed.  
Twenty subjects were admitted to the final database (15 male, 1 female, 2 non-binary, 2 dummy mannequins, ages: 20-63 (majority 20-30)). Inclusion was subject to the quality of their measurements determined by observational notes and analysis of spectral, Interaural Time Difference (ITD) and Interaural Level Difference (ILD) plots. One subject voluntarily stopped the measurement procedure part way though. Six subjects were excluded due to excessive movement and shuffling in-between measurements. Two subjects were excluded due to minor asymmetries in their ITD plots. Two subjects were excluded due to unexplained discontinuities in their measurements, possibly a result of movement. Qualifying datasets included those of the KU100 dummy head and KEMAR mannequin.  
Data is available for download on the database webpage: www.york.ac.uk/sadie-project/database.html.