Group 13: Scott DiStefano, Kahri Olsen, Alex Orbach, & Kenneth - - PowerPoint PPT Presentation

Group 13: Scott DiStefano, Kahri Olsen, Alex Orbach, & Kenneth Meerendonk Advisor: Professor Prasad

Table of Contents

• The Human Cochlea
• Types of Cochlea Damage
• Existing Technologies
• Conceptual Design 1
• Conceptual Design 2
• Comparison of Designs
• Budget
• Project Schedule
• Conclusion

How Sound Is Processed

The Human Cochlea

The Human Cochlea

• Comprised of three fluid filled parts
• Scala Vestibuli- perilymph fluid
• Scala Tympani- perilymph fluid
• Scala Media- endolymph fluid
• Organ of Corti
• Thousand of hair cells convert motion to

electrical signals

• Main Function
• Collect sound waves from the external

ear

• Converts movement of hair cells into an

electrical signal that are communicated to neurotransmitters

• Electrical impulses become action

potentials which travel along the auditory nerve to the brainstem

Inside the human cochlea (Charles Gary Wright, Ph.D. and Peter S. Roland, M.D. )

Three Tiny Bones of the Middle Ear

• Malleus
• Attached to the mobile part of the

ear drum

• Receives vibration and starts
• scillating motion
• Incus
• Acts as a bridge or connector from

malleus to stapes

• Transmits motion to the stapes
• Stapes
• Smallest named bone in the human

body

• Causes movement of the fluid inside

the cochlea

Bones of the inner ear. (Hearing Central)

Organ of Corti

• Contains auditory sensory cells, or “hair cells”
• Between 15,000-20,000 total
• Transduces pressure waves to action potentials
• Stimulate the spiral ganglion
• Sends information to the auditory portion of the eighth cranial nerve
• Travels to the brain for processing

What is Sensorineural Hearing Loss?

• Damage to the inner ear nerves or

hair cells

• Permanent
• Potentially caused by:

– Genetics or abnormal inner ear development – Injury from medicine or disease – Tumor – Physical injury to the inner ear

Examples of Hair Cells

Normal Cochlea Damaged Cochlea http://acousticsweb.com/education/demos/hearing_loss/hearing_loss.html

FACTS:

• Approximately 17% of Americans (~36

million) suffer from some degree of hearing loss

• 7.4% of Americans 29-40 years old suffer from

hearing loss

• “Cochlear implantation consistently ranks

among the most cost-effective medical procedures ever reported.”

• Average Cost of implants: $40,000
• “Net savings greater than $53,000 per child”

The American Speech-Language Hearing Association

Existing Technologies

www.thehearinginstitute.org

Existing Technologies

Problems with Existing Technologies

• Currently no Exclusively

Internal device

• External Device creates

buzzing/humming

• External is non-aesthetic
• Implants don’t replicate

entire cochlea function

www.terptopics.com/HearingAids.htm

CONCEPTUAL DESIGN 1

• Human cochlea acts as a bank of high Q resonators
• Uses resonator bars in fishbone design (Tanaka, Abe &

Ando)

Resonator Bars

Design Alternatives…

CONCEPTUAL DESIGN 1 cont.

• Will be housed in non-rigid

material, tapered to accommodate resonator bars

• Human cochlea stops

almost all reflections so only the purest sounds are picked up

• Inside of housing will be

sound absorptive

The use of foams or rubbers will absorb sound (AcoustiProducts)

MATERIALS

• Piezoelectrics – Quartz, PZT,

PVDF

• Lead zirconate titanate -

ceramic

• Polyvinylidene fluoride –

thermoplastic polymer

• Medical grade silicone
• Acoustic foam or dense rubber

(a) Structure of PZT; (b) under influence

• f an electric field (The Open

University) Varying widths of silicone tubing (Qmed)

Resonance

• Sound waves are mechanical
• scillations of pressure through a

solid, liquid or gas

• Resonator bars move depending on

each bars natural frequency

• NF of Bar =

𝑙 𝑛

2𝜌 (k=stiffness; m=mass)

• NF of Sound =

𝑤 4𝑀

The collapse of the Tacoma Narrows Bridge due to resonance (Science Clarified)

Circuitry & Calculations

• Stress: 𝜏 =

𝐺 𝑚−𝑧 𝑑 𝐽𝑑

• Change in Resistance:

∆𝑆 𝑆 = 6𝜌(𝑚−

𝑚𝑚𝑓𝑕 2 )

𝑥𝑢3

𝐺

• Resistance will be found using

Wheatstone Bridge

• Uses Kirchoff’s 1st and 2nd Laws
• High accuracy for known R’s, then

high accuracy for found R

Conceptual Design Two

Design Alternatives…

Configuration of Design Two

Modeling the Cochlea

• Single Linear fluid duct replaces complex spiral shape
• Duct dimensions constant along length
• Rigid structure
• Fluid interacts with only bottom of membrane
• Position of maximum membrane distortion a function of incoming

frequency

• Position to frequency mapping similar to that of the biological cochlea
• Output of sensors used to determine input frequencies

Simpli lifi fica cati tions:

• ns:

Performan rformance ce Characteris cteristic tics: s: Variation of membrane properties Cross-section of Design Two

Design Two Details

• Sensors are piezoelectric cantilevers
• Design mimics hair cell function
• Output voltage of each sensor varies with stress
• Given beam dimensions, displacement at the tip can be calculated
• LABView or similar program will receive and interpret output signals

from device

• Simplified model of the biological cochlea
• Single fluid filled duct housed within rigid structure
• Flexible membrane with varying dimensions
• Microphone input to generate incoming vibrations
• Sensors along length of membrane which measure displacement

due to pressure waves in fluid

Overview:

Technical Analysis

Design sign Parameter ameters: s: Helmholtz 2-D Equation: Partial Differential Equation

Analysis obtained from Michigan University research:

• R. White and K. Grosh, Microengineered Hydromechanical Cochlear Model.

Design Evaluations

• Responds to a wide range of

input frequencies

• Provides unlimited number of
• utput positions
• Scaled-down implant size

version possible using MEMS

• Straightforward technical

analysis

• Sensors outside of the fluid

duct

Advantage ntages: s: Disadva dvantage ntages: s:

Design 1:

• No fluid to aid in the propagation of

sound waves

• Needs sound absorption inside

housing

• Sensors are difficult to fabricate

Design 2:

• Precision/accuracy vary with

calibration

• Membrane increases design

complexity

Expected Budget

Project Schedule