Effect of low-frequency gain and venting effects on the benefit derived from directionality and noise reduction in hearing aids

Keidser, Gitte; Carter, Lyndal; Chalupper, Josef; Dillon, Harvey

doi:10.1080/14992020701481698

Cited by 18 publications

(11 citation statements)

References 39 publications

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“…The effect was explained by the cardioid microphone characteristic being the only signal processing scheme that offered different gain for sounds arriving from the frontal and rearward directions, thus providing alternative cues, such as differences in overall loudness, to the monaural spectral cues. This fi nding has since been confi rmed by Keidser et al ( 2007 ). In that study, 21 hearing-aid users signifi cantly improved front/back localization when fi tted with wide dynamic range compression (WDRC) combined with noise reduction and a directional hyper-cardioid microphone, than when fi tted with WDRC only.…”

mentioning

confidence: 70%

The effect of frequency-dependent microphone directionality on horizontal localization performance in hearing-aid users

Keidser

O'Brien

Hain

et al. 2009

International Journal of Audiology

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Frequency-dependent microphone directionality alters the spectral shape of sound as a function of arrival azimuth. The influence of this on horizontal-plane localization performance was investigated. Using a 360 degrees loudspeaker array and five stimuli with different spectral characteristics, localization performance was measured on 21 hearing-impaired listeners when wearing no hearing aids and aided with no directionality, partial (from 1 and 2 kHz) directionality, and full directionality. The test schemes were also evaluated in everyday life. Without hearing aids, localization accuracy was significantly poorer than normative data. Due to inaudibility of high-frequency energy, front/back reversals were prominent. Front/back reversals remained prominent when aided with omnidirectional microphones. For stimuli with low-frequency emphasis, directionality had no further effect on localization. For stimuli with sufficient mid- and high-frequency information, full directionality had a small positive effect on front/back localization but a negative effect on left/right localization. Partial directionality further improved front/back localization and had no significant effect on left/right localization. The field test revealed no significant effects. The alternative spectral cues provided by frequency-dependent directionality improve front/back localization in hearing-aid users.

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confidence: 70%

The effect of frequency-dependent microphone directionality on horizontal localization performance in hearing-aid users

Keidser

O'Brien

Hain

et al. 2009

International Journal of Audiology

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“…Unfortunately, higher gain settings are often not possible due to the large amount of sound leaking out of the ear canal. Keidser, Carter, Chalupper, and Dillon (2007) measured how much low-frequency gain is preferred by listeners to compensate for leakage out of the ear canal through the vent. Hearing-impaired listeners were fitted with BTE or ITE hearing aids with clinically appropriated vent sizes.…”

Section: Open-fit Hearing Aidsmentioning

confidence: 99%

“…Horizontal localization performance was also analyzed in the study of Keidser et al. (2007) described earlier.…”

Section: Advantages Of Open-fit Hearing Aidsmentioning

confidence: 99%

“…Hearing-impaired listeners were fitted with BTE or ITE hearing aids with clinically appropriated vent sizes. Keidser et al (2007) evaluated hearing-aid settings that differed in the amount of real-ear insertion gain at 250 Hz for a 65 dB SPL broadband speech-weighted noise signal and in the activation or deactivation of adaptive features (directional microphone and noise reduction). The evaluation of the various settings was carried out using different methods.…”

Section: Fitting Of Open-fit Hearing Aidsmentioning

confidence: 99%

“…Horizontal localization performance was also analyzed in the study of Keidser et al (2007) described earlier. The listeners were fitted with BTE hearing aids and individual earmolds, or ITEs with different vent sizes (1.5 mm up to open).…”

Section: Localizationmentioning

confidence: 99%

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Open Versus Closed Hearing-Aid Fittings: A Literature Review of Both Fitting Approaches

2016

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One of the main issues in hearing-aid fittings is the abnormal perception of the user’s own voice as too loud, “boomy,” or “hollow.” This phenomenon known as the occlusion effect be reduced by large vents in the earmolds or by open-fit hearing aids. This review provides an overview of publications related to open and closed hearing-aid fittings. First, the occlusion effect and its consequences for perception while using hearing aids are described. Then, the advantages and disadvantages of open compared with closed fittings and their impact on the fitting process are addressed. The advantages include less occlusion, improved own-voice perception and sound quality, and increased localization performance. The disadvantages associated with open-fit hearing aids include reduced benefits of directional microphones and noise reduction, as well as less compression and less available gain before feedback. The final part of this review addresses the need for new approaches to combine the advantages of open and closed hearing-aid fittings.

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Spatial Hearing and Hearing Aids

Akeroyd

Whitmer

2016

Hearing Aids

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Spatial hearing is a central part of everyday listening. The ability to determine the direction of a sound source is a natural and effortless skill that is only remarked on in rare or challenging circumstances, such as when a driver cannot determine the direction of the siren of a passing ambulance. But spatial hearing performance by hearing-impaired listeners is considerably degraded, and generally hearing aids do not offer any benefit.In most circumstances -excepting only if a sound source is exactly directly ahead, above, or behind -the fine details of a sound's waveform at the left ear will differ in some way from those at the right ear. The auditory system is sensitive to these interaural ("between the ears") differences. Imagine that the source is to the right of someone's head. The left ear is further from the source than the right ear, by about 18-20 cm, so the sound will arrive there a fraction of a millisecond after it arrives at the right ear. The left ear is also in the acoustic shadow cast by the head, so the sound's level will be less there than at the right ear. Both interaural cues physically occur at all frequencies, but their importance varies with frequency. The interaural level differences (ILDs) can reach 20 or 30 dB at frequencies around 5-10 kHz, but are less than 5 dB below 500 Hz. ILDs are therefore generally regarded as being most useful at high frequencies. Conversely, the interaural time differences (ITDs) -at most, about 600-800 millionths of a second -are primarily a lowfrequency cue, useful up to around 1500 Hz Many laboratory experiments have demonstrated that normal-hearing listeners are remarkably sensitive to these two cues: at best, people can discriminate changes of about 0.5 dB of ILD or 10 millionths of a second of ITD. But in everyday listening people are never called onto discriminate pure changes in ILD or ITD in isolation: when the direction of a source changes, both cues vary. At best, the discrimination for changes in direction is about 1 degree of spatial angle. This is the "minimal audible angle": one can reliably distinguish the left vs. right direction of two sounds, presented in quiet, 1 degree apart. These measurements can be made directly using very closely-spaced loudspeakers or with robot arms to accurately move loudspeakers by very small amounts. An alternative approach is to use a fixed loudspeaker array with relatively large spacing between loudspeakers, such as 15 degrees, and then measure how inaccurate listeners are at reporting the direction of sounds presented from them.One degree of angle is really not very much: it corresponds to the apparent width of the index fingernail held at arm's length. Comparative measurements in mammals have demonstrated that humans have amongst the best performance: of all species measured so far; only dolphins and elephants do as well or better (Heffner, 2004). It is curious why we should be so good at distinguishing sound direction in quiet. Perhaps it is a by-product -an evolutionary spandrel (Gould and Lewontin, 1979) ...

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Effect of low-frequency gain and venting effects on the benefit derived from directionality and noise reduction in hearing aids

Cited by 18 publications

References 39 publications

The effect of frequency-dependent microphone directionality on horizontal localization performance in hearing-aid users

The effect of frequency-dependent microphone directionality on horizontal localization performance in hearing-aid users

Open Versus Closed Hearing-Aid Fittings: A Literature Review of Both Fitting Approaches

Spatial Hearing and Hearing Aids

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