1. 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

2. 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

3. 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

4. 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

5. Ear and Head dimensions of 1059 UG students

6. 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

7. 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

8. 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)

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

10. 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

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

12. 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

13. 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

14. Experiment design of HRTF measurements

15. 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

16. 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

17. Experiment design of HRTF measurements

18. 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.

19. 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

20. 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

21. 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

22. Q & A