# A Review on Head-Related Transfer Function Generation for Spatial Audio
## Appendix A
The database 3D3A (2017) [91] contains HRIRs of 38 subjects considering 648 positions with the elevation ranging from \(-30^{\circ}\) to 75\({}^{\circ}\) and azimuth from 0\({}^{\circ}\) to 360\({}^{\circ}\) with a resolution of 5\({}^{\circ}\). The measurements are conducted with an arc of eight Genelec 8030A loudspeakers with a radius of \(0.76\pm 0.005\) and binaural microphones from Theoretica Applied Physics BACCH-BM Pro. All measurements are conducted at a sampling rate of 96 kHz, and the sine sweep signals have a duration of 500 ms. The HRIRs have a duration of 10 ms, corresponding to a length of 960 samples. The 3D morphological scans of the torso, head, and ears of the subjects are available. The database SADIE II (2018) [16] is a follow-on from the original database SADIE [228]. It contains the HRIRs of 29 human subjects and the two HAT simulators Neumann KU100 and Kemar. A regular latitude-longitude distribution (15\({}^{\circ}\) elevation and variable azimuthal resolution) is considered. Twenty-three Genelec 8010S loudspeakers are installed at 23 unique elevations at a radius of 1.2 m. With the mannequins, 8802 directions are involved, and with subjects 2818 or 2114. The HRIRs have a length of 512 samples and are measured with exponential sine sweep using a sample rate of 96 kHz. However, sample rates of 48 kHz and 44.1 kHz are also available. Anthropometric data, such as 3D head scans and high-resolution pictures of the ear, are included. The HUTUBS database (2019) [89] considers 94 human subjects and a FABIAN HAT simulator [232]. It consists of 440 measurement points, including elevations from \(-90^{\circ}\) to 90\({}^{\circ}\) with 10\({}^{\circ}\) increment and different azimuth resolutions depending on the elevation (\(\geq\)10\({}^{\circ}\)). The measurement system consists of 37 Peerless NE65-04 2-inch drivers. The distance from the centre of the array to the membrane of the speakers is 1.47 m. HRIRs, 256 samples long, are then measured under continuous rotation of the subject using NLMS adaptive filters and a sampling frequency of 44.1 kHz. In total, 93 sets of anthropometric measures and 58 head meshes are available. The database VIKING (2019) [230] comprises full-sphere HRTFs measured on 1513 positions with a [PERSON] mannequin with 20 different pairs of artificial pinnae attached. The [PERSON] mannequin is mounted on a 360\({}^{\circ}\) rotating cylindrical stand, and a Genelec 8020 CPM-6 loudspeaker is mounted on an L-shaped rotating arm. Elevations from \(-45^{\circ}\) to 90\({}^{\circ}\) uniformly sampled in \(5^{\circ}\) are considered, and azimuths are sampled in different increments (\(\geq\)5\({}^{\circ}\)). The HRIRs of 128-samples length are measured with a logarithmic sweep using a sample rate of 48 kHz. The SONICOM database (2023) [90] considers 120 subjects and 828 positions. An arch of 23 full-range Peerless 830987 3-in drivers is used between \(-45^{\circ}\) and \(225^{\circ}\) of elevation, spaced every \(10^{\circ}\) between \(-30^{\circ}\) /30\({}^{\circ}\) and \(150^{\circ}\)/210\({}^{\circ}\) and spaced every \(15^{\circ}\) in the other positions. The distance between the loudspeaker drivers and the centre of the arch is 1.5 m. The HRIRs are measured with multiple exponential sweeps with a sample rate of 96 kHz, and widowed to a length of 512 samples. In addition, 3D models of ears, head, and torso are also available. The database LORIS (2024) [66] is built from a non-uniform set of dynamic data measurements taken from a single subject. The elevations have a range from \(-42^{\circ}\) to \(42^{\circ}\), approximatively, and the azimuths are non-uniformly distributed in the 360\({}^{\circ}\) full range for a total of 8186 positions. The HRIRs have a length of 8192 samples and are acquired with a sample rate of 48 kHz. A 3D model of the head is also provided.