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J Am Acad Audiol 1999; 10(08): 458-465
DOI: 10.1055/s-0042-1748519
Original Article

Variables Affecting the Use of Prescriptive Formulae to Fit Modern Nonlinear Hearing Aids

Francis K. Kuk
Widex Hearing Aid Company, USA, Long Island City, New York
,
Carl Ludvigsen
Widex ApS, Denmark
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Abstract

It is routine for audiologists to fit nonlinear hearing aids by using one of several current prescriptive formulae. While such an approach might result in acceptable fittings for single-channel analog compression hearing aids, its direct application to fitting current multichannel compression hearing aids may result in less than an optimal fit. In this paper, the effects of filter bandwidth, number of channels, detector type, compression threshold, attack and release times, and distortion on the final output of a nonlinear compression hearing aid are discussed. The subjective results of such effects and its implications on our clinical practice will be explored as well.

Abbreviations: CR = compression ratio, CT = compression threshold, DSL (i/o) = Desired Sensation Level (input/output), FFT = Fast Fourier Transform, HA = hearing aid, IHAFF = Independent Hearing Aid Fitting Forum, I/O = input/output, LGOB = Loudness Growth by Octave Band, RMS = root mean square, UCL = uncomfortable listening level, WDRC = wide dynamic range compression

Key Words

Attack and release times - compression thresholds - detectors - distortion - expansion processing - filter bandwidth - filter channels - prescriptive formulae


Publication History

Article published online:
03 May 2022

© 1999. American Academy of Audiology. This article is published by Thieme.

Thieme Medical Publishers, Inc.
333 Seventh Avenue, 18th Floor, New York, NY 10001, USA

 

  • REFERENCES

  • Agnew J. (1998). The causes and effects of distortion and internal noise in hearing aids. Trend Ampi 3:82-118.
  • Allen J, Hall JL, Jeng P. (1990). Loudness growth in 1/2 octave bands (LGOB): a procedure for the assessment of loudness. J Acoust Soc Am 88: 745–753.
  • Byrne D. (1996). Hearing aid selection for the 1990s: where to? J Am Acad Audiol 7: 377–395.
  • Cornelisse L, Seewald R, Jamieson D. (1994). The input/output (I/O) formula: a theoretical approach to the fitting of personal amplification devices. J Acoust Soc Am 97: 1854–1864.
  • Dillon H, Storey L, Grant F, Phillips A, Skelt L, Mavrias G, Woytowych W, Walsh M. (1998). Preferred compression threshold with 2:1 wide dynamic range compression in everyday environments. Aust J Audiol 20: 33–34.
  • Fortune T, Preves D, Woodruff B. (1991). Saturation induced distortion and its effects on aided LDL. Hear Instr 42(10): 37, 40, 42.
  • Hellman R, Meiselman C. (1990). Loudness relations for individuals and groups in normal and impaired hearing. J Acoust Soc Am 88: 2596–2606.
  • Killion M, Fikret-Pasa S. (1993). The 3 types of sensorineural hearing loss: loudness and intelligibility considerations. Hear J 46(11): 31–36.
  • Kuk F. (1996). The effects of distortion on user satisfaction with hearing aids. In: Valente Μ, ed. Hearing Aids: Standards, Options, and Limitations. New York: Thieme Medical Publishing, 327–367.
  • Kuk F. (1998). Rationale and requirements for a slow acting compression hearing aid. Hear J 51(6): 45–53, 79.
  • Launer S. (1995). Loudness Perception in Listeners with Sensorineural Hearing Impairment. Doctoral dissertation, University of Oldenburg, Germany.
  • Lechtenberg C. (1998, June). Comparison between Fitting the Senso Hearing Aid with Its Own Proprietary Formula versus Matching the Output to the DSL[i/o] Target. Paper presented at the Widex Barcelona Technology Update, Barcelona, Spain.
  • Ludvigsen C, Topholm J. (1997). Fitting a wide dynamic range compression hearing instrument using real ear threshold data: a new strategy. In: Kochkin S, Strom K, eds. Hear Rev (Suppl) High Performance Hearing Solutions: Vol 2: Marketing and Technology. 37–39.
  • Lynn G, Carhart R. (1963). Influence of attack and release in compression amplification on understanding speech by hypoacoustics. J Speech Hear Disord 28: 124–140.
  • Naidoo S, Hawkins D. (1997). Monaural/binaural preferences: effect of hearing aid circuit on speech intelligibility and sound quality. J Am Acad Audiol 8: 188–202.
  • Neuman A, Bakke M, Mackersie C, Hellman S, Levitt, H. (1995). Effect of release time in compression hearing aids: paired-comparison judgments of quality. J Acoust Soc Am 98: 3182–3187.
  • Neuman A, Bakke M, Mackersie C, Hellman S, Levitt H. (1998). The effect of compression ratio and release time on the categorical rating of sound quality. J Acoust Soc Am 103: 2273–2281.
  • Pascoe D. (1988). Clinical measurements of the auditory dynamic range and their relations to formulas for hearing aid gain. In: Hartvig Jenson J, ed. Procedings of the 13th Danavox Symposium. 129–151.
  • Schweitzer H, Causey G. (1977). The relative importance of recovery time in compression hearing aids. Audiology 16: 61–72.
  • Stone MA, Moore BCJ. (1992). Syllabic compression: effective compression ratios for signals modulated at different rates. Br J Audiol 26: 351–361.
  • Valente Μ, Van Vliet D. (1997). The independent hearing aid fitting forum (IHAFF) protocol. Trend Ampi 2: 6–35.
  • Valente Μ, Fabry D, Potts L, Sandlin R. (1998). Comparing the performance of the Widex Senso digital hearing aid with analog hearing aids. J Am Acad Audiol 9: 342–360.
  • Verschuure J, Maas AJ, Stikvoort E, de Jong RM, GoedegebureA, Dreschler WA. (1996). Compression and its effect on the speech signal. Ear Hear 17: 162–175.