# A Review on Head-Related Transfer Function Generation for Spatial Audio
## Appendix A
The SYMARE database provides both acoustically measured HRIRs and HRIRs simulated using the BEM. Multiple high-resolution surface mesh models of the upper torso, head, and ears are provided. The TUM-LDV database (2013) [225] contains the HRIRs and the anthropometric parameters of 35 human subjects and two Kemar mannequins. The acoustic measurement per elevation is achieved by a continuous counter-clockwise turn from \(-30^{\circ}\) to \(370^{\circ}\) covering a full loop with an azimuth resolution of \(1^{\circ}\) or \(0.2^{\circ}\) considering 6 elevations in the range from \(-50^{\circ}\) to \(230^{\circ}\). The HRIRs have a length of 1024 samples, measured with a dynamic NLMS approach using a sampling frequency of 48 kHz. The ARI database (2014) [13] is acquired by mounting twenty-two Vifa 10 BGS loudspeakers at fixed elevations from \(-30^{\circ}\) to \(80^{\circ}\). The subject is seated in the centre of the arc with a radius of 1 m, has in-ear Sennheiser KE-4-211-2 microphones, and can rotate, varying the azimuth with variable steps \(\geq 2.5^{\circ}\). The dataset covers 1550 directions of the sphere and includes more than 250 subjects. The HRIRs are measured using the multiple exponential sweep method (MESM) using a sample rate of 48 kHz and a length of 256 samples. The anthropometric data of 60 listeners are also provided. The database RIEC (2014) [226] includes the HRIRs of 105 subjects and 936 directions covered by a vertical circular loudspeaker array consisting of 35 Fostex FE83E loudspeakers. The loudspeakers are arranged at intervals of 10\({}^{\circ}\) of the elevation angle from \(-80^{\circ}\) to 90\({}^{\circ}\). The circular loudspeaker array can automatically rotate around the vertical axis; a resolution of 5\({}^{\circ}\) is chosen for the azimuth. The distance between the centre of the subject's head and each loudspeaker is 1.5 m. The HRIRs are measured using the optimised Aoshima's time-stretched pulse (OATSP) [231] as a source signal with a length of 8192 samples and a sampling frequency of 48 kHz. Anthropometric data for 39 subjects are also included. For the BiLi (2015) [227] dataset, the head-related impulse responses of 56 subjects are measured in the IRCAM's anechoic chamber using the exponential sweep sine technique, non-coaxial two-way ELAC 301 loudspeakers, and a sampling rate of 96 kHz. Knowles FG26107 microphones are positioned at the entrance of the blocked ear canal. The spatial sampling scheme is based on a Gaussian grid and includes 1680 directions with a full azimuth range, and elevation ranging from \(-51^{\circ}\) to \(86^{\circ}\). The angular step size is approximately 6\({}^{\circ}\) in both dimensions. A database of 3D morphological data is also included. The database SADIE (2015) [228] contains measurements from 20 human subjects and two dummy heads, i.e., a Neumann KU100 and a Kemar mannequin. For the subjects, 170 measurement points are considered, while 1550 positions are used for the mannequin. The distribution of the points covers the overall sphere surface and satisfies Ambsonic decoding up to the fifth order. They also contain reference measurements at azimuthal increments of 5\({}^{\circ}\), only at 0\({}^{\circ}\) elevation for the subjects, and in steps of elevation of 10\({}^{\circ}\) for the mannequins. The HRIRs are 256 samples long that were measured using logarithmic sine sweeps at a sampling frequency of 44.1 kHz. The ITA database (2016) [229] contains the 256-samples HRIRs of 48 subjects measured in 2304 positions with Sennheiser KE3 microphones using a sample rate of 44.1 kHz. The azimuth and the elevation have a resolution of 5\({}^{\circ}\), and the elevation varies from \(-66^{\circ}\) to 90\({}^{\circ}\). A vertical arc of 64 1\" broadband speakers is used for the measurements, and HRIRs are measured using the multiple-exponential sweep method. Three-dimensional models of the ear geometry, reconstructed from magnetic resonance imaging scans, are included.