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Just noticeable and objectionable group delays in digital hearing aids
1Starkey Laboratories, Inc., Eden Prairie, Minnesota, USA.
Journal of the American Academy of Audiology
|June 17, 2000
Summary
Digital signal processing (DSP) hearing aids can create echoes. Delays over 3-5 milliseconds are noticeable, and over 10 milliseconds are objectionable to users hearing their own voice.
Area of Science:
- Audiology
- Signal Processing
- Human-Computer Interaction
Background:
- Group delay in digital signal processing (DSP) hearing aids can cause audible echoes of a user's own voice.
- This echo results from the combination of direct sound and delayed amplified sound, potentially leading to auditory confusion.
Purpose of the Study:
- To investigate the audibility and objectionability thresholds of group delay in DSP hearing aids.
- To determine user perception of self-voice delay in amplified sound.
Main Methods:
- 18 subjects listened to their own amplified voices through a DSP hearing aid with adjustable group delay.
- Participants identified noticeable and objectionable delay levels compared to an undelayed condition.
Main Results:
- A group delay of 3 to 5 milliseconds was noticeable in 76% of trials.
- Delays exceeding 10 milliseconds were deemed objectionable in 90% of trials.
Conclusions:
- Group delay in DSP hearing aids significantly impacts user perception of their own voice.
- Specific delay thresholds (3-5ms noticeable, >10ms objectionable) can guide hearing aid design to minimize user discomfort.