Tympan Rev C - Independent Testing Data and Specs

Joshua M. Alexander of Purdue University presented a great round-up of independent testing data on the Tympan Rev C at the ASA 2018 Meeting. Here are some excerpts from "Audiologic Evaluation of the Tympan Open Source Hearing Aid"

Summary

1.Throughput delay: acceptable with basic WDRC

2.Internal noise: expansion needed to make acceptable

3.Maximum output: ~110 dB SPL w/ minimal distortion

4.Total harmonic distortion: 90 dB SPL input; 50 dB gain

5.Frequency response: smooth with gain/input changes

6.Compression parameters: WDRC parameters as advertised; OLC able to control max output

7.Directionality: basic using mini boom mic

8.Audiometric fitting range: ≤ 70-75 dB HL

9.Probe microphone feasibility: YES

 

Metrics Evaluated

1.Throughput delay: 

  • 5.7 sec as measured using a Frye Fonix 7000 hearing aid analyzer

2.Internal noise:

  • Equivalent Input Noise (EIN)
  • Expansion activated

 

3.Maximum output:

  • 90-dB SPL tones; flat 10-40 dB linear gain

4.Total harmonic distortion:

  • Distortion only when output level is high. Indicates that the front-end components (microphone, ADC, etc.) are not in saturation with high input levels


5.Frequency response:

  • Relatively flat (300-4000 Hz), unvarying across changes in gain and input level
  • Output levels are effectively limited by OLC (BOLT)
  • Less effective for low frequencies à distortion (not shown)
  • Gain decreases with increasing input level (WDRC)
  • Distortion ‘free’ gain at least up to 40-50 dB

6.Compression parameters:

  • WDRC CT = 50 dB SPL, CR = 1.5:1; OLC = 105 dB

7.Directionality:

KEMAR

  • Mounted on right ear; flat 20 dB linear gain

  • Low distortion for 65 dB SPL input (0-2%)
  • Higher EIN (44 dB SPL) due to lack of expansion, equivalent to Sony omni mic (46 dB SPL) 

Test Box

  • WDRC for a mild to moderate hearing loss

8.Audiometric fitting range

  • Hearing losses up to 70-75 dB HL can easily be accommodated
  • Can amplify soft speech with relatively modest internal noise and amplify high-level narrowband sounds with relatively low distortion for these losses

9.Probe microphone feasibility:

  • Tympan can be tested like a regular hearing aid

 

   

Thank you to Dr. Joshua Alexander at Purdue and the team at the Purdue EAR lab.