Supervisor: Dr Richard So Speaker: Brian Ngan Ear and head dimensions measurement and Experiment design of HRTF measurement Supervisor: Dr Richard So Speaker: Brian Ngan

Contents Introduction Ear and Head dimensions of 1059 UG students Motivation Data collected Methodology of measurement Next step Experiment design of HRTF measurements Preparation of Manikin head Preparation of external ear model Design of experiment Summary Q & A

Introduction Sound Localization of human Filtering effect of pinna, head and torso Brain process those data and percept an auditory event Head-related Transfer function (HRTF) Frequency responses and time delay between sounds that originate from different positions and their corresponding destination of sounds measured between the ear canals and the pinnae

Introduction The shape of ear and head is highly correlated to Head-Related Transfer Function (HRTF) Clustering people according to their ear and head dimensions

Ear and Head dimensions of 1059 UG students

Ear and Head measurements Motivation Study the relationship between ear/head dimensions and sound localization performance Cluster subjects and collect a set of HRTF from each cluster

Data collected 1059 UG students 610 males, 449 females Head dimensions Ear and Head measurements Data collected 1059 UG students 610 males, 449 females Head dimensions Chin to top of head Bitragion Breadth Head Length

Data collected Ear dimensions d1 cavum concha height Ear and Head measurements Data collected Ear dimensions d1 cavum concha height d2 cymba concha height d3 cavum concha width d4 fossa height d5 pinna height d6 pinna width d7 intertragal incisure width From V. R. Algazi et. al. (2001)

Methodology of measurement Ear and Head measurements Methodology of measurement Head measurement Using anthropometer to measure

Methodology of measurement Ear and Head measurements Methodology of measurement Ear measurement Using digital camera to take ear photos Measure different dimensions with a program provided by Mr. Leung Wai Keen

Methodology of measurement Ear and Head measurements The program that used for ear measurement

Next step…. The progress: ear measurement Ear and Head measurements Next step…. The progress: ear measurement Cluster subjects according to their ear/head dimensions Invite students from each cluster to be subjects of sound localization performance experiment Check if the sound localization performance is different in different cluster

Next step…. Collect 1 or 2 subjects’ ear models from each cluster Ear and Head measurements Next step…. Collect 1 or 2 subjects’ ear models from each cluster Measure sets of HRTF from those ear models Verify those HRTFs if it gives a good sound localization performance for people belonged to that cluster

Experiment design of HRTF measurements

Motivation Investigate the effect of head size on HRTF Experiment design of HRTF measurements Motivation Investigate the effect of head size on HRTF Investigate which type of material (wax or ABS) is more suitable for making HRTF-measurement-purpose manikin head Investigate the differences of HRTF between human and manikin head with ear model

Preparation of Mannequin head Experiment design of HRTF measurements Preparation of Mannequin head Dimensions: 5%tile, 50%tile and 95%tile of head height, breath and length of male data collected in UST Using rapid prototype machine to make the model FDM – ABS (a kind of polymer) ThermoJet – Wax

Experiment design of HRTF measurements

Preparation of external ear model Experiment design of HRTF measurements Preparation of external ear model Dr. Aaron Leung (certified prosthetist-orthotist) helped making external ear model Ear models are made of silicon 2 sets of external ear models were made now (Brian’s and Dr. So’s) Will invite 2 more subjects.

Experiment design of HRTF measurements Design of experiment Due to limitation of time, it may only possible to collect 20 set of HRTF Material deciding : 1,2,3 Head size effect: 1,7,8 Individual difference: 1,4,5,6 *Numbers are the working sequence   Wax ABS 95%tile 50%tile 5%tile Real Brian 7 1 8 15 2 16 3 Ear Dr So 9 4 10 20 17 21 - Subject 1 11 5 12 22 18 23 Subject 2 13 6 14 24 19 25

Design of experiment What I am expecting: Experiment design of HRTF measurements Design of experiment What I am expecting: Wax head will give nearer values of real man HRTF than ABS The head size does not affect too much on HRTF The shape of external ear (pinna) contributes most part of HRTF HRTF collected will give high sound localization performance to its owner

Summary We have collected 1059 students’ head dimensions and ear photos We are going to test which material is the best for HRTF measurement Test the differences of HRTF collected with human and manikin head

Q & A