SYMARE database version 0.9 - 20/03/2014

INTRODUCTION

The result of collaboration between the Universities of York and Sydney for
over ten years, the SYMARE database supports research exploring the
relationship between the morphology of human outer ears and their acoustic
filtering properties - a relationship that is viewed by many as holding the key
to human spatial hearing and the future of 3D personal audio. 

The SYMARE database is comprised of acoustically measured head-related impulse
response filters (HRIR filters) for 61 listeners (48 male/13 female), multiple
high-resolution surface mesh models (upper torso, head and ears) for these
listeners obtained from magnetic resonance imaging (MRI) data, and the
corresponding simulated HRIR data generated using the Fast-Multipole Boundary 
Element Method (FM-BEM).


DESCRIPTION OF THE DATABASE

The directory structure of the SYMARE database is shown below:

SYMARE
+---HRIRs 
|   +---Acoustic 
|   +---Bem 
|   |   +---HE16kHz 
|   |   \---HTE05kHz 
|   \---Parameters 
\---Meshes 
    +---BemReady 
    |   +---HeadAndEars 
    |   |   +---04kHz 
    |   |   +---08kHz 
    |   |   +---12kHz 
    |   |   +---16kHz 
    |   |   \---20kHz 
    |   \---HeadTorsoAndEars 
    |       +---04kHz 
    |       +---08kHz 
    |       +---12kHz 
    |       +---16kHz 
    |       \---20kHz 
    \---HighResolution 
        +---HeadAndEars 
        +---HeadAndTorso
        +---HeadTorsoAndEars 
        +---LeftEar 
        \---RightEar 

The SYMARE database is comprised of two types of data: 1) Acoustic data, in the
form of Head Related Impulse Response filters (HRIR filters) ; 2) Morphological
data, in the form of triangular surface meshes of human ears, heads and torsos.

1. Acoustic data

The directory "HRIRs" contains the acoustic data. Two types of HRIR filters are
provided. The "Acoustic" directory contains the acoustically measured HRIR 
filters for every subject. The "Bem" directory contains BEM-simulated HRIR 
filters. Two sub-directories are located under Bem: the directory "HE16kHz" 
contains HRIR filters obtained using "Head and ears" meshes valid up to about
16 kHz; The directory "HTE05kHz" contains HRIR filters obtained using "Head,
torso, and ears" meshes valid up to about 5 kHz. All BEM simulations were run
using COUSTYX by Ansol.

All the sets of HRIR filters are provided as Matlab *.mat files that contain
two matrix variables: hL, the left-ear HRIRs, and hR, the right-ear HRIRs. The
dimension of these matrices is 256 x 393, corresponding to 256 time samples and
393 angular directions.

Lastly, the directory named "Parameters" contains the parameters common to 
every set of HRIR filters:
- "azim" and "elev", the 393 azimuths and elevations for which the HRIR filters
  are provided, in radians. Note that we use Matlab's convention for spherical 
  coordinates (elev goes from -pi/2 to pi/2).
- "r", the distance to the acoustic source (1m).
- "fs", the sampling frequency (48000 Hz).
- "rho", the density of air at 20 degrees Celsius. (1.2 kg.m-3).
- "c", the speed of sound at 20 degrees Celsius. (343 m.s-1).
Note that the two last parameters only concern the BEM simulations

2. Morphological data

The directory "Meshes" contain the morphological data. Two classes of meshes
are provided. The "BemReady" directory contains meshes of "Head and ears" 
and meshes of "Head, torso and ears" suitable for BEM simulations up to the 
frequencies 4 kHz, 8 kHz, 12 kHz, 16 kHz and 20 kHz. Every mesh meets the 
following quality criterions:
- the longest triangle edge is shorter than a sixth of the wavelength at the
  specified maximum frequency.
- the ratio of the longest triangle edge over the shortest is less than 5.
- the minimum triangle angle is greater than 15 degrees.

The "HighResolution" directory contains high-resolution meshes of the subjects'
morphology. Five types of meshes are provided: 
- Head, torso and ears (HTE)
- Head and ears (HE) - no torso.
- Head and torso (HT) - no ears.
- Left ear (LE).
- Right ear (RE).
Note that the BEM-ready meshes were obtained by coarsening the high-resolution
HTE and HE meshes.

All meshes are provided as binary *.PLY files. 


REMARKS

- PLY files can be easily imported in Matlab using the PLYio toolbox, available
  online at the address below:
  http://people.sc.fsu.edu/~jburkardt/m_src/ply_io/ply_io.html

- *.mat files can be opened using OCTAVE, which is freely available.
 
- We are currently in the process of re-running BEM simulations for all the
  subjects in the database. These simulations are run with the 20 kHz HTE 
  and HE meshes using the Burton-Miller BEM formulation. The obtained HRIR 
  filters will be added to the version 1.0 of the database.


ACKNOWLEDGMENTS

- The creation of the SYMARE database was supported by the Australian Research
  Council (Discovery Project DP110102920) and the UK Engineering and Physical 
  Sciences Research Council (grant GR/T28140/01).
  
- We thank the company ANSOL (Advanced Numerical Solutions) for letting us use
  COUSTYX and for their technical support.