Ear and head dimensions measurementEar and head dimensions measurementandand

Experiment design of HRTF Experiment design of HRTF measurementmeasurement

Supervisor: Dr Richard SoSupervisor: Dr Richard SoSpeaker: Brian NganSpeaker: Brian Ngan

ContentsContents• Introduction• Ear and Head dimensions of 1059 UG students

– Motivation– Data collected– Methodology of measurement– Next step

• Experiment design of HRTF measurements– Motivation– Preparation of Manikin head– Preparation of external ear model– Design of experiment

• Summary• Q & A

IntroductionIntroduction• 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

IntroductionIntroduction• 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 Ear and Head dimensions of dimensions of

1059 UG 1059 UG studentsstudents

MotivationMotivation• Study the relationship between

ear/head dimensions and sound localization performance

• Cluster subjects and collect a set of HRTF from each cluster

Ear and Head measurements

Data collectedData collected• 1059 UG students• 610 males, 449

females• Head dimensions

– Chin to top of head– Bitragion Breadth– Head Length

Ear and Head measurements

• 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

Ear and Head measurements

Data collectedData collected

From V. R. Algazi et. al. (2001)

Methodology of Methodology of measurementmeasurement

• Head measurement– Using anthropometer to measure

Ear and Head measurements

Methodology of Methodology of measurementmeasurement

• Ear measurement– Using digital

camera to take ear photos

– Measure different dimensions with a program provided by Mr. Leung Wai Keen

Ear and Head measurements

Methodology of measurementMethodology of measurementEar and Head measurements

The program that used for ear measurement

Next step….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

Ear and Head measurements

Next step….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

Ear and Head measurements

Experiment Experiment design of HRTF design of HRTF measurementsmeasurements

MotivationMotivation• 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

Experiment design of HRTF measurements

Preparation of Mannequin Preparation of Mannequin headhead

• 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

Experiment design of HRTF measurements

Preparation of external ear Preparation of external ear modelmodel

• 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 experimentDesign 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

Experiment design of HRTF measurements

  Wax     ABS    

   95%til

e50%til

e 5%tile95%til

e50%til

e 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 -

*Numbers are the working sequence

Design of experimentDesign 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

Experiment design of HRTF measurements

SummarySummary• 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 & AQ & A