Just Noticeable and Objectionable Group Delays in Digital Hearing Aids

Abstract

Group delay in a digital signal processing (DSP) hearing aid may be perceived as an echo in the sound heard by a wearer listening to his or her own voice, due to a combination of unprocessed sound received at the ear through head and air pathways and delayed sound reaching the eardrum through the hearing aid. Depending on the amount, this delay may be audible or objectionable and can even result in auditory confusion. This study presents results from 18 subjects listening to their own voices through a DSP hearing aid with a variable group delay. The subjects varied the length of the delay and determined the amounts that were noticeable and objectionable as compared to the undelayed condition, while listening to their own amplified voices. Results indicated that a delay of 3 to 5 msec was noticeable to the listeners in 76 percent of the trials, and a delay of longer than 10 msec was objectionable 90 percent of the time.

Abbreviations: DAF = delayed auditory feedback, DSP = digital signal processing, KEMAR = Knowles Electronics manikin for acoustic research

Key Words

Delay perception - digital signal processing - digital signal processing hearing aids - group delay

Publikationsverlauf

Artikel online veröffentlicht:
08. April 2022

• REFERENCES

• Agnew J. (1997). An overview of digital signal processing in hearing instruments. Hear Rev 4(7):8, 12, 16, 18, 66.
• Ballou G. (1987). Filters and equalizers. In: Ballou G, ed. Handbook for Sound Engineers. Indianapolis, IN: Howard W. Sams, 569–612.
• Borden GJ, Harris KS. (1984). Speech Science Primer. 2nd Ed. Baltimore: Williams & Wilkins.
• Cabot RC. (1988). Audio tests and measurements. In: Benson KB, ed. Audio Engineering Handbook. New York: McGraw-Hill, 16.1–16.72.
• MacKay DG. (1970). Spoonerisms: the structure of errors in the serial order of speech. Neuropsychologia 8:323–350.
• Moser LM. (1999). Electro-acoustic Measurements of Hearing Aids with Digital Signal Processing—What Is Needed in Addition to the Standards IEC-118 and ANSI-322? Poster session presented at the Hearing Aid Amplification for the New Millennium conference, Sydney, Australia, November 15–19, 1999.
• Silman S, Silverman CA. (1991). Auditory Diagnosis: Principles and Applications. San Diego: Academic Press.
• Stone MA, Moore BCJ. (1999). Tolerable hearing aid delays. I. Estimation of limits imposed by the auditory path alone using simulated hearing losses. Ear Hear 20:182–192.
• Summerfield Q. (1992). Lipreading and audio-visual speech perception. Philos Trans R Soc Lond Β Biol Sci 335:71–78.