Transcript DHA Directional Hearing Aid - University of California

DHA
Directional Hearing Aid
Team Members:
Noah Van Fossan
Shareen Hossain
Deepthi Chandra
Christina Clemenz
Laura Hanley
Advisors:
Prof. Mark Bell
Prof. Carla Zoltowski
Project Partner:
Prof. Robert Novak
DHA
Directional Hearing Aid
Project Goal
To design and develop an inexpensive hearing
aid that will cancel out background noise so that
a person with a hearing impairment can carry out
a conversation in a noisy environment.
Overview
Four microphones forming a linear
array are embedded on an eyeglass
frame and connected to a circuit
which is is largely responsible for
the noise cancellation effect.
DHA
Directional Hearing Aid
Microphone Array Theory
All microphones must be separated by a fixed distance
to produce maximum cancellation of unwanted signals.
Input and summing stages must have similar impedances
so they do not cause a phase shift inside of the circuit.
Having the microphones spaced four centimeters apart
increases directionality for high frequencies because of
their short wavelength.
Low frequencies would require a larger spacing between
microphones.
DHA
Directional Hearing Aid
Frequency Range Theory
The frequency range is from 500Hz to 5.5KHz.
Adjustable lower
frequency cutoff switch- 500Hz to
1.5KHz
• Human ear loses high frequency first so more
emphasis must be placed upon the base.
Cascading low
frequency range.
and high pass filters create the desired
DHA
Directional Hearing Aid
Semester Accomplishments
• new circuit built, in testing phase
• Increased gain to 45 dB
• Finished auto-off design
• debugging circuit antenna problem
• redesigning the virtual ground
DHA
Directional Hearing Aid
Current Circuit
DHA
Directional Hearing Aid

Summing amplifier and High pass stage.
• Directionality and low frequency cutoff
occur in this stage

Low pass Stage
• High frequencies are cutoff at this
stage.

Gain Stage
• The output signal is amplified during this
phase.
DHA
Directional Hearing Aid
Debugging Process
• Antenna Problem Input
• Voltage leads act as an antenna and is bringing in a
frequency of 33KHz
DHA
Directional Hearing Aid
Debugging Process
Flaws in Virtual Ground Design
• Large current cannot be drawn from current design
• Gain loss occurs when a load resistance (headphones) is
attached
Current Virtual Ground
DHA
Directional Hearing Aid
Proposed Solutions
Solution for antenna problem.
• Relocate circuit to protoboard.
New
virtual ground design
DHA
Directional Hearing Aid
Implementation of auto-off feature
Future Circuit Design
DHA
Directional Hearing Aid
Future Semester Goals
Producing the Product
1. Build Prototype of new circuit
2. Perform various tests
Post prototype lab test
Human subject test
3. Deliver the product
SEM
Sound Exposure Meter
Presented by:
Maggie Zhu
Jason Kaeding
Greg Moore
Guy Barcelona
Jamy Archer
Project Partner – Dr. Robert Novak,
M. D. Steer Audiology Clinic at Purdue
Project Objectives

Alert user when
noise level could
cause hearing
damage

Easy to use, easy
to understand

Small size (i.e. a
pager)
Desired Functionality

Instantaneous indicator
• Current noise level > 85dBA

Average level indicator
• Avg. noise level for 1 min. > 85dBA

Impulse noise indicator
• Avg. frequency of impulses in excess of
110dBA > 1 per 3 sec.
Overview of
Circuit Design
Average Level
Indicator
Instantaneous Indicator
Impulse Noise
Indicator
Semester
Accomplishments

Evaluated and consolidated impulse
noise indicator section

Redesigned A-weighting filter

Created test plan
Impulse Noise Indicator

Tested current hardware
configurations

Consolidated counters and
comparator into PLD

Added continuous testing
functionality.
Filter Design

Goal: accurately model A-weighting
transfer function
Filter Design
 Design
completed
• Three sections
•
Each realizes one part of the transfer
curve
•
Used active Sallen and Key circuits
• SPICE simulation
•
Max. deviation < 0.6dB
Test Plan

Designed for the overall circuit

Includes a standardized procedure
and safety concerns

Compares circuit response to the
response of Sound Level Meter
Future Plans

Individually test each functional
block

Fine tune reference voltages in
comparators

Complete new circuit diagram

Implement test plan for whole circuit
VLM
Voice Level Meter
Tim Chuah
Jason Fluckey
Valerie Lamott
Erica Lute
Nate Miller
Project Partner – Dr. Robert Novak,
M. D. Steer Audiology Clinic at Purdue
Problem Identification
Audiology Clinic needs a visual
means of measuring speech volume.
 Existing device, Spright II, has been
discontinued.

Improvements
Existing device is not very accurate.
 Longer cord or battery operated.
 Improve LED display readability.

Design Concept
5 10-segment LED
bar graphs
 Range of 40-89dB

Block Diagram
Circuit Diagram
Project Status
Low pass filter has been built and it
works.
 Second low pass filter was designed
and it also has been built and works.
 Log amp has been built and it
works.
 Microphone through log amp
working together

Future Plans
Add potentiometers
 Work on driver chips
 Work on casing
