DHA Directional Hearing Aid Team Members Noah Van

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 500 Hz to 5. 5 KHz. ®Adjustable lower frequency cutoff switch- 500 Hz to 1. 5 KHz • Human ear loses high frequency first so more emphasis must be placed upon the base. ®Cascading low and high pass filters create the desired frequency range.

DHA Directional Hearing Aid Semester Accomplishments • new circuit built, in testing phase • Increased gain to 45 d. B • 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 33 KHz

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 n Alert user when noise level could cause hearing damage n Easy to use, easy to understand n Small size (i. e. a pager)

Desired Functionality n Instantaneous indicator • Current noise level > 85 d. BA n Average level indicator • Avg. noise level for 1 min. > 85 d. BA n Impulse noise indicator • Avg. frequency of impulses in excess of 110 d. BA > 1 per 3 sec.

Overview of Circuit Design Average Level Indicator Instantaneous Indicator Impulse Noise Indicator

Semester Accomplishments n Evaluated and consolidated impulse noise indicator section n Redesigned A-weighting filter n Created test plan

Impulse Noise Indicator n Tested current hardware configurations n Consolidated counters and comparator into PLD n Added continuous testing functionality.

Filter Design n Goal: accurately model A-weighting transfer function

Filter Design n Design completed • Three sections • Each realizes one part of the transfer curve • Used active Sallen and Key circuits • SPICE simulation • Max. deviation < 0. 6 d. B

Test Plan n Designed for the overall circuit n Includes a standardized procedure and safety concerns n Compares circuit response to the response of Sound Level Meter

Future Plans n Individually test each functional block n Fine tune reference voltages in comparators n Complete new circuit diagram n 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. n Existing device, Spright II, has been discontinued. n

Improvements Existing device is not very accurate. n Longer cord or battery operated. n Improve LED display readability. n

Design Concept 5 10 -segment LED bar graphs n Range of 40 -89 d. B n

Block Diagram

Circuit Diagram

Project Status Low pass filter has been built and it works. n Second low pass filter was designed and it also has been built and works. n Log amp has been built and it works. n Microphone through log amp working together n

Future Plans Add potentiometers n Work on driver chips n Work on casing n