Digital Feedback Suppression (DFS): Clinical Experiences when Fitting a DFS Hearing Instrument on Children

Henningsen, Lise B.; Dyrlund, Ole; Bisgaard, Nikolai; Brink, Birthe

doi:10.3109/01050399409047495

Cited by 6 publications

(2 citation statements)

References 2 publications

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“…One important advance in hearing instrument technology has been the development of feedback suppression systems. Some of these systems provide higher maximum stable gain by the use of feedback cancellation filters (Dyrlund and Bisgaard, 1991;Murray and Hanson, 1992;Dyrlund et al, 1994;Henningsen et al, 1994;Greenberg et al, 2000). While this added feedback margin may be considered as means to protect hearing instrument wearers from ever experiencing feedback, it may also be utilized to provide greater venting than the desired gain settings would otherwise allow.…”

mentioning

confidence: 99%

Occlusion Effect of Earmolds with Different Venting Systems

Kießling¹,

Brenner²,

Jespersen³

et al. 2005

J Am Acad Audiol

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In this study the occlusion effect was quantified for five types of earmolds with different venting. Nine normal-hearing listeners and ten experienced hearing aid users were provided with conventional earmolds with 1.6 and 2.4 mm circular venting, shell type earmolds with a novel vent design with equivalent cross-sectional vent areas, and nonoccluding soft silicone eartips of a commercial hearing instrument. For all venting systems, the occlusion effect was measured using a probe microphone system and subjectively rated in test and retest sessions. The results for both normal-hearing subjects and hearing aid users showed that the novel vents caused significantly less occlusion than the traditional vents. Occlusion effect associated with the soft silicone eartip was comparable to the nonoccluded ear. Test-retest reproducibility was higher for the subjective occlusion rating than for the objectively measured occlusion. Perceived occlusion revealed a closer relationship to measured occlusion in the ear in which the measured occlusion effect was higher ("high OE" ear) than in the "low OE" ear. As our results suggest that subjective judgment of occlusion is directly related to the acoustic mass of the air column in the vent, the amount of perceived occlusion may be predicted by the vent dimensions.

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mentioning

confidence: 99%

Occlusion Effect of Earmolds with Different Venting Systems

Kießling¹,

Brenner²,

Jespersen³

et al. 2005

J Am Acad Audiol

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“…The circuit provides approximately 10 dB of additional usable real ear gain Smriga, 1993). A study of ten children, fitted binaurally, by Henningsen et al (1994) reported that 5 dB to 10 dB of additional usable gain in the low, mid and high frequency regions was available.…”

Section: Adaptive Cancellation Filtermentioning

confidence: 99%

Acoustic Feedback and Other Audible Artifacts in Hearing Aids

Agnew

1996

Trends in Amplification

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A coustic feedback has been described as "whistling," "howling," "screeching," "screaming," 'squealing,'" "whining,'" "ringing, " "humming," "buzzing." "oscillating" and by various other names. The high-pitched whistling of a hearing aid experiencing acoustic feedback is an irritating sound for the hearing aid wearer and for nearby individuals. Suppressing these irritating squealing noises is not easy. Thus dealing with acoustic feedback is still a prevalent problem that plagues clinicians and wearers alike. Though specific figures are considered by manufacturers to be proprietary information, industry experts estimate that as many as 10% to 15% of in-the-ear hearing aid products are likely to be returned to the factory within the first 90 days after manufacture for feedback-related problems. Obviously this adds to the overall cost of hearing aids to the dispenser, and anything that can be done to help reduce these returns will ultimately benefit the wearer.This issue is intended to provide comprehensive information on the origins and characteristics of acoustic feedback in hearing aids and to discuss its minimization or prevention. Although it will primarily discuss acoustic feedback, for completeness the discussion will also include the audible symptoms of electrical and electromagnetic feedback and pickup. These also occur in hearing aids and are frequently confused by the wearer with acoustic feedback. Some discussion of the symptoms of both may help the clinician to understand and resolve complaints of oscillations and other audible artifacts in a troublesome hearing aid fitting. It is useful for the clinician to be able to distinguish between various manifestations of oscillation and other audible sounds in order to be able to logically identify the problem and counsel the wearer appropriately.Before starting a detailed discussion of feedback, an important point should be made concerning terminology. Acoustic feedback in a hearing aid fitting produces a form of instability and the resulting audible oscillation. It is caused by a sound wave from the output leaking back to the input. Though all acoustic feedback of the correct phase and magnitude produces an undesired form of oscillation in a hearing aid, not all oscillation is due to acoustic feedback. In precise terms the objectionable audible sound produced by a hearing aid due to acoustic feedback should be called audible oscillation due to acoustic feedback. Through common usage, this more accurate term has generally been abbreviated simply to acoustic feedback, though in reality acoustic feedback is the cause of the problem and not the audible effect. However, to comply with common usage the term acoustic feedback will be used consistently throughout the text to refer to the unpleasant and undesired squealing and screeching that occurs in a hearing aid and which is caused by the leakage of amplified output sound back to the microphone.A second point should also be made about terminology. For simplicity, hearing aids will be discussed in two general ca...

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Simulated real-ear measurements of benefit from digital feedback suppression

Olsen

2008

International Journal of Audiology

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Digital feedback suppression (DFS) enables users of hearing instruments (HI) to benefit from amplification levels that normally would provoke whistling or poor sound quality. A standardized test for the measurement of DFS benefit is not available. This paper proposes and evaluates an objective method for assessment of extra feedback-free amplification (headroom) provided by a given DFS. It is shown that the whistle-free loop gain can be calculated from data obtained with simulated real-ear measurements with the modified pressure method. Test-retest trials were carried out to assess the reliability of the proposed method. Also, a method was developed for defining an appropriate gain level at which the proposed measurement should be carried out. It is concluded that the proposed method needs to be modified to provide useful information.

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Digital Feedback Suppression (DFS): Clinical Experiences when Fitting a DFS Hearing Instrument on Children

Cited by 6 publications

References 2 publications

Occlusion Effect of Earmolds with Different Venting Systems

Occlusion Effect of Earmolds with Different Venting Systems

Acoustic Feedback and Other Audible Artifacts in Hearing Aids

Simulated real-ear measurements of benefit from digital feedback suppression

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