DHA D irectional H earing A id

2. 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

3. 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.

4. 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.

5. 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 and high pass filters create the desired frequency range.

6. 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

7. DHA Directional Hearing Aid Current Circuit

8. 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.

9. DHA Directional Hearing Aid Debugging Process • • Antenna Problem Input • Voltage leads act as an antenna and is bringing in a frequency of 33KHz

10. 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

11. DHA Directional Hearing Aid Proposed Solutions • Solution for antenna problem. • Relocate circuit to protoboard. • New virtual ground design

12. DHA Directional Hearing Aid Implementation of auto-off feature Future Circuit Design

13. DHA Directional Hearing Aid Future Semester Goals Producing the Product • Build Prototype of new circuit • 2. Perform various tests • Post prototype lab test • Human subject test • 3. Deliver the product

18. 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

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

20. 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.

21. Instantaneous Indicator Average Level Indicator Impulse Noise Indicator Overview ofCircuit Design

22. SemesterAccomplishments • Evaluated and consolidated impulse noise indicator section • Redesigned A-weighting filter • Created test plan

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

24. Filter Design • Goal: accurately model A-weighting transfer function

25. 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

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

27. Future Plans • Individually test each functional block • Fine tune reference voltages in comparators • Complete new circuit diagram • Implement test plan for whole circuit

29. 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

30. Problem Identification • Audiology Clinic needs a visual means of measuring speech volume. • Existing device, Spright II, has been discontinued.

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

32. Design Concept • 5 10-segment LED bar graphs • Range of 40-89dB

33. Block Diagram

34. Circuit Diagram

35. 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

36. Future Plans • Add potentiometers • Work on driver chips • Work on casing