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PubMed2006

Effects of programming threshold and maplaw settings on acoustic thresholds and speech discrimination with the MED-EL COMBI 40+ cochlear implant.

OBJECTIVES: The principal task in the programming of a cochlear implant (CI) speech processor is the setting of the electrical dynamic range (output) for each electrode, to ensure that a comfortable loudness percept is obtained for a range of input levels. This typically involves separate psychophysical measurement of electrical threshold ([theta] e) and upper tolerance levels using short current bursts generated by the fitting software. Anecdotal clinical experience and some experimental studies suggest that the measurement of [theta]e is relatively unimportant and that the setting of upper tolerance limits is more critical for processor programming. The present study aims to test this hypothesis and examines in detail how acoustic thresholds and speech recognition are affected by setting of the lower limit of the output ("Programming threshold" or "PT") to understand better the influence of this parameter and how it interacts with certain other programming parameters. DESIGN: Test programs (maps) were generated with PT set to artificially high and low values and tested on users of the MED-EL COMBI 40+ CI system. Acoustic thresholds and speech recognition scores (sentence tests) were measured for each of the test maps. Acoustic thresholds were also measured using maps with a range of output compression functions ("maplaws"). In addition, subjective reports were recorded regarding the presence of "background threshold stimulation" which is occasionally reported by CI users if PT is set to relatively high values when using the CIS strategy. RESULTS: Manipulation of PT was found to have very little effect. Setting PT to minimum produced a mean 5 dB (S.D. = 6.25) increase in acoustic thresholds, relative to thresholds with PT set normally, and had no statistically significant effect on speech recognition scores on a sentence test. On the other hand, maplaw setting was found to have a significant effect on acoustic thresholds (raised as maplaw is made more linear), which provides some theoretical explanation as to why PT has little effect when using the default maplaw of c = 500. Subjective reports of background threshold stimulation showed that most users could perceive a relatively loud auditory percept, in the absence of microphone input, when PT was set to double the behaviorally measured electrical thresholds ([theta]e), but that this produced little intrusion when microphone input was present. CONCLUSIONS: The results of these investigations have direct clinical relevance, showing that setting of PT is indeed relatively unimportant in terms of speech discrimination, but that it is worth ensuring that PT is not set excessively high, as this can produce distracting background stimulation. Indeed, it may even be set to minimum values without deleterious effect.

Acoustic Stimulation↗
PubMed2002

Influence of benzodiazepines on auditory perception.

The aim of this study was to test for an influence of benzodiazepine (BZD) on various perceptual and/or cognitive auditory processes. Loudness, auditory selective attention, and the ability of subjects to form perceptual streams out of alternating tone sequences were tested. Nine subjects were tested before, 1, 3, 7, and 24 h after a single-dose oxazepam vs placebo administration in a crossover design. A sample of blood allows us to measure plasma oxazepam concentration. The results revealed a significant reduction in stream segregation expressed as d' scores 1 h after oxazepam intake in the test subjects. No significant change occurred across time in the same subjects when they were administrated a placebo in another session. Furthermore, oxazepam had no substantial and systematic influence either on auditory selective attention or on loudness perception. Altogether, these results suggest that the perceptual organization of sound sequences involves inhibitory neural mechanisms, which can be affected by BZDs. This outcome is consistent with existing models of auditory stream segregation and may be paralleled with earlier findings on the effect of BZDs on perceptual binding in the visual modality.

Acoustic Stimulation↗
PubMed1994

An in vitro study of mechanical heart valve sound loudness.

The purpose of the study was to measure the valve sound loudness of eight 25 mm aortic mechanical heart valve prostheses under controlled laboratory conditions in an isolated acoustic environment. A specially designed single-chamber pulse duplicator was constructed within an anechoic box that isolated the sounds of the valve from external noise. The valves were closed with a stimulated aortic pressure waveform of three different amplitudes. Valve sound loudness was measured with ISO-532/B (Zwicker method), which is based on a model of loudness perception that is better than dB(A), the traditional A-weighted sound pressure level. The average loudness for each valve was St. Jude Medical, 0.97 sones; CarboMedics, 0.98 sones; Sorin Biomedica Bicarbon, 1.08 sones; Edwards Tekna, 1.92 sones; Edwards Duromedics, 2.36 sones; Monostrut, 2.48 sones; Sorin Biomedica Carbocast, 3.17 sones; and Medtronic Hall, 3.57 sones. There was a positive trend between valve sound loudness and aortic drive pressure for most valves in the study.

Aortic Valve↗
PubMed1989

Phoneme perception via hearing aids with and without compression and the role of temporal resolution.

Hearing impairment is more than a sensitivity loss. The causes of reduced discrimination can be found also in deteriorations in loudness perception (recruitment), frequency resolution and temporal resolution. Only recruitment can be compensated for by modern hearing aids, namely by the reduction of the dynamic range by means of compression. However, the introduction of compression introduces temporal distortions, which may deteriorate the temporal cues of speech. In this study the perception of nonsense consonant-vowel-consonant-words presented through hearing aids was studied in a group of 12 hearing-impaired listeners. Phoneme perception in conditions with and without compression was analyzed and related to temporal parameters of the listeners' hearing. A detailed analysis of the patterns of confusions revealed clear qualitative differences in the perception of phonemes with and without compression. These differences can be related to an improved perception of temporal cues like the preburst silent interval of plosives and to spectral changes induced by the activation of the compression circuit. A reduced temporal resolution is disadvantageous for the perception of temporal cues like plosive detection, but our data do not suggest that the perception of temporal cues is hampered excessively by temporal distortions from the compression circuit itself.

Adolescent↗
PubMed1989

Extracochlear electrical stimulation.

Twelve patients with sensorineural hearing loss were stimulated by a transtympanic electrode contacting the cochlear promontory. Nine of them were tested to study hearing perception associated with various features of electrical signals, using an auditory electrical stimulator. Biphasic pulse bursts and sine-wave bursts were used as stimuli. Different electrical characteristics such as amplitude, width and rate for pulses and amplitude and frequency for sine waves were used to investigate hearing perception. The patients' perception threshold, comfortable level, uncomfortable level, dynamic range, just-noticeable difference in frequency or pitch discrimination, just-noticeable difference in intensity or loudness discrimination, loudness perception associated with the electrical signal energy, and sounds associated with electrical stimulation was determined. Pertinent results assisted in the development of a speech electrical stimulator that was used to test three patients for vowel, word, and consonant identification and recognition of patterns of intonation. These results in turn are being used to design a prototype of a single-channel extracochlear prosthesis.

Acoustic Stimulation↗
PubMed1998

Accuracy of predicted ear canal speech levels using the VIOLA input/output-based fitting strategy.

OBJECTIVE: The Visual Input/Output Locator Algorithm (VIOLA) is a software-assisted method for prescribing amplification targets and selecting a hearing aid to match the targets. Although the procedure calls for selection and fitting of hearing aids in terms of their pure-tone input/output functions in a coupler, it is assumed that a hearing aid that matches the coupler prescription targets will produce specific amplified speech levels in the patient's ear canal. This investigation evaluated the validity of that assumption. DESIGN: Six hearing aids were evaluated. They were representative of linear and compression processing as well as single- and 2-channel designs. The "subject" was a KEMAR manikin with realistic assumed hearing loss and loudness perception characteristics. Each hearing aid was configured to match the subject's VIOLA prescription as closely as possible. Predicted ear canal speech levels were determined using the prescription rules and modified by the differences between coupler prescription targets and coupler performance of the actual hearing aids. With the subject wearing each hearing aid coupled to an unvented earmold, continuous speech was presented in the sound field and measured, after amplification, in the ear canal. The match between observed and predicted levels of amplified speech indicated the validity of the VIOLA assumptions under examination. RESULTS: The match between predicted and observed levels was good for soft speech input levels. As speech input levels increased, the differences between observed and predicted levels also increased, with the largest differences seen for loud speech inputs. When differences were seen between observed and predicted levels, they were always in the direction of lower than predicted ear canal levels. The differences between observed and predicted levels were attributed to the effects of limiting, effects of compression ratio in wide range compression, the individual subject's field-to-microphone transfer function, and the subject's individual real-ear-to-coupler level difference. CONCLUSIONS: Ear canal speech levels were reasonably close to predicted values, and the deviations from predicted levels were plausibly accounted for by consideration of hearing aid performance. Thus, the approach used by the VIOLA procedure holds considerable promise for extending clinical control over the complex and interactive parameters of nonlinear hearing aids. The results of this study indicate that selection and fitting of hearing aids using the current VIOLA procedure usually will result in the generation of lower than predicted ear canal speech levels, especially for loud speech inputs. However, the accuracy of the procedure could be improved substantially by modification of the software to account for the effects of limiting and those of the compression ratio in systems with compression thresholds lower than the level of unamplified loud speech.

Ear Canal↗
PubMed1982

Frequency and intensity effects on ear dominance for tone bursts.

Normal-hearing Ss (N = 20) listened to dichotic pairs of 20-msec tones at 0.4, 1.5, or 3 kc/s differing by 76, 224, or 376 c/s between the two ears and also differing by 0, 15, or 35 db in SPL (the more intense tone always at 80 db SPL). S judged each pair "high-low" or "low-high" in pitch. Earlier investigations have shown that many normal-hearing Ss demonstrate a dominance for pitch perception of one ear over the other which is unaltered by large interaural intensity differences. In this study, ear dominance could be modified by a change in frequency location or interaural frequency difference of the dichotic stimuli. The effect of interaural level differences could be seen at all frequency conditions, but was strongest at low frequencies. It was suggested that ear dominance on this perceptual task is governed by several characteristics of the auditory system, including loudness perception, dichotic fusion, and frequency selectivity, as well as some as-yet ill-defined binaural processes.

Acoustic Stimulation↗
PubMed2005

Auditory gap detection in the early blind.

For blind individuals, audition provides critical information for interacting with the environment. Individuals blinded early in life (EB) typically show enhanced auditory abilities relative to sighted controls as measured by tasks requiring complex discrimination, attention and memory. In contrast, few deficits have been reported on tasks involving auditory sensory thresholds (e.g., Yates, J.T., Johnson, R.M., Starz, W.J., 1972. Loudness perception of the blind. Audiology 11(5), 368-376; Starlinger, I., Niemeyer, W., 1981. Do the blind hear better? Investigations on auditory processing in congenital or early acquired blindness. I. Peripheral functions. Audiology 20(6), 503-509). A study of gap detection stands at odds with this distinction [Muchnik, C., Efrati, M., Nemeth, E., Malin, M., Hildesheimer, M., 1991. Central auditory skills in blind and sighted subjects. Scand. Audiol. 20(1), 19-23]. In the current investigation we re-examined gap detection abilities in the EB using a single-interval, yes/no method. A group of younger sighted control individuals (SCy) was included in the analysis in addition to EB and sighted age matched control individuals (SCm) in order to examine the effect of age on gap detection performance. Estimates of gap detection thresholds for EB subjects were nearly identical to SCm subjects and slightly poorer relative to the SCy subjects. These results suggest some limits on the extent of auditory temporal advantages in the EB.

Adult↗
PubMed2000

Discharge rate of the auditory nerve during noise revealed by electrocochlear stimulation.

The purpose of this study was to evaluate the average discharge rate of all fibres in the whole auditory nerve (R(wn)) when a broad-band noise with steady-state effects is applied to the ear. We assessed the R(wn) parameter by detecting the state of refractoriness of the nerve during noise stimulation using an electric stimulus (ES) as a probe. The technique, applied in awake pre-implanted guinea pigs (Charlet de Sauvage et al., 1994), made it possible to obtain electro-acoustic responses (EARs), from which an estimate of the R(wn) parameter could be deduced. Negative current pulses of 100 micros duration, each followed by an identical pulse of positive polarity for charge balance, were applied between round window and indifferent vertex electrodes at intervals of 160 ms. The 120 ms wide-band noise masker started 92 ms before every other negative ES. The signal on the stimulating electrodes was averaged over a 5.12 ms window in synchrony with the negative pulse. EARs were obtained by alternately subtracting recordings during noise from those during silence. The R(wn) parameter was determined by comparing experimental and computed EAR patterns. For this purpose, a model of unit response incorporating changes in amplitude and conduction velocity during the relative refractory period was designed. The recovery function of the firing probability in response to ES was evaluated. Fibres were classified in different categories according to their background discharge rates. The probability of response of single fibres to ES in each category was calculated on the basis of their interval histograms during silence and noise. Individual spikes were combined accordingly to obtain the computed EAR waveform. R(wn) was determined by adjusting the EAR amplitude of the model in relation to that of the experimental EAR. R(wn) generally increases in a linear fashion with respect to noise intensity expressed in dB, thus following the increase in loudness perception estimated by Weber's law. At the highest noise levels, R(wn) tends to saturate. The estimated saturation rate was found to be about 380 spikes/s.

Animals↗
PubMed1980

Ontogeny of the acoustic startle response in C57BL/6J mouse pups.

A cross-sectional design was used to study the development of acoustic startle behavior in C57BL/6J mice from the approximate onset of hearing (12 days) to 17 days of age. Startle incidence and latency were recorded in response to 5-, 7-, 10-, 15-, and 20-kHz tones each presented at 80, 90, and 100 dB (SPL). From 12 to 17 days of age, higher frequency and lower intensity tones became increasingly effective in eliciting the acoustic startle response. In addition, startle latency decreased substantially, and response incidence became more sensitive to changes in tone intensity and tone frequency. This rapid ontogeny of the acoustic startle response closely parallels previously demonstrated neurophysiological development of the mouse pup auditory system.

Aging↗
PubMed1981

Regulation of vocal intensity in the presence of feedback filtering and amplification.

Subjects read while their voices were fed back with 0 and 20 dB of amplification. In Experiment I, feedback was returned unfiltered or low-pass filtered with cut-off frequencies of 1000, 500, and 300 Hz. Subjects decreased vocal intensity with amplified feedback when the feedback was unfiltered or low-pass filtered with cut-off frequencies of 1000 or 500 Hz. The amplification effect disappeared when the cut-off frequency was 300 Hz. In Experiment II, feedback was low-pass filtered and amplified in the presence of a steady background noise. The presence of noise potentiated the amplification effect in the unfiltered condition. When filtering was introduced and/or the cut-off frequency was lowered, the amplification effect decreased. In Experiment III, subjects heard their voices unfiltered and high-pass filtered with cut-off frequencies of 500, 1000, and 2000 Hz. The amplification effect was the same across filtering conditions. It is suggested that subjects respond differently and high- and low-pass filtering because air- and bone-conducted feedback interact differentially in these conditions. It is hypothesized that changes may be mediated by self-perception of loudness or intelligibility.

Adult↗
PubMed2004

Psychometric evaluation of children with suspected auditory processing disorders (APDs) using a parent-answered survey.

Difficulty with auditory processing in children is of increasing interest but is the subject of some controversy in the literature This paper describes a psychometric evaluation of differences between children with suspected auditory processing disorders (APDs) and a control group, using a parent-answered questionnaire. The questionnaire comprised 51 items associated with auditory processing as well as speech/language- and behaviour-related areas. It was found that most of the items separated significantly (p<0.01) between the children with suspected APDs and the control group. A factor analysis identified seven components (speech understanding in demanding situations, speech/language abilities, general behavioural issues, reactions to questions and demands, discrimination of speech sounds, musical cues, loudness perception) underlying the contrasts between the two study populations. The examination might serve as a basis for the development of an APD-related questionnaire. However, the validity of such a questionnaire is questionable at present, since APD is not very well specified, and standardized diagnostic tests are lacking.

Auditory Perceptual Disorders↗
PubMed1980

Magnitude of the acoustic reflex for either homophasic (0 degrees) or antiphasic (180 degrees) binaural activating signals presented in a background of noise.

The threshold of the acoustic reflex (TAR) and the magnitude of middle-ear muscle response were measured for a homophasic (0 degrees) and an antiphasic (183 degrees) 550-Hz tone in a background of in-phase noise. Signal-to-noise ratio ranged from - 20 dB to 5 dB. Whereas previously reported data shows an effect of phase on the percept of loudness, no evidence of a phase effect was measured for acoustic-reflex responses. These results are interpreted as evidence against a relation between loudness and acoustic reflex for binaurally presented signals.

Acoustic Stimulation↗
PubMed2000

The dynamic range of inner hair cell and organ of Corti responses.

Inner hair cell (IHC) and organ of Corti (OC) responses are measured from the apical three turns of the guinea pig cochlea, allowing access to regions with best, or most sensitive, frequencies at approximately 250, 1000, and 4000 Hz. In addition to measuring both ac and dc receptor potentials, the average value of the half-wave rectified response (AVEHR) is computed to better reflect the signal that induces transmitter release. This measure facilitates comparisons with single-unit responses in the auditory nerve. Although IHC ac responses exhibit compressive growth, response magnitudes at high levels depend on stimulus frequency. For example, IHCs with moderate and high best frequencies (BF) exhibit more linear responses below the BF of the cell, where higher sound-pressure levels are required to approach saturation. Because a similar frequency dependence is observed in extracellular OC responses, this phenomenon may originate in cochlear mechanics. At the most apical recording location, however, the pattern documented at the base of the cochlea is not seen in IHCs with low BFs around 250 Hz. In fact, more linear behavior is measured above the BF of the cell. These frequency-dependent features require modification of cochlear models that do not provide for longitudinal variations and generally depend on a single stage of saturation located at the synapse. Finally, behavior of dc and AVEHR responses suggests that a single IHC is capable of coding intensity over a large dynamic range [Patuzzi and Sellick, J. Acoust. Soc. Am. 74, 1734-1741 (1983); Smith et al., in Hearing--Physiological Bases and Psychophysics (Springer, Berlin, 1983); Smith, in Auditory Function (Wiley, New York, 1988)] and that information compiled over wide areas along the cochlear partition is not essential for loudness perception, consistent with psychophysical results [Viemeister, Hearing Res. 34, 267-274 (1988)].

Animals↗
PubMed1989

[Subjective noise perception and objective measurement of loudness following heart valve replacement with the St. Jude Medical and Duromedics Edwards bileaflet prostheses].

The performance of heart valve prostheses is generally judged by the rate of valve-related complications and the hemodynamic performance. Patients may be severely bothered by the metallic click generated by the closure of the valve. In 74 patients after valve replacement with Duromedics Edwards (DE) (n = 38) and St. Jude Medical (SJM) (n = 36) prostheses the sound energy was recorded and correlated to the complaints of the patients. At a distance of 10 cm the DE valves produced a significantly higher sound pressure with 47 +/- 7 db(A) compared to the SJM valves with 39.8 +/- 5 db(A) (p = 0.001). The noise level was also different for the valves in aortic or mitral position. After splitting into frequency bands the highest sound pressure was observed in the high frequency ranges (8 to 16 kHz) which represents the metallic click. 65% of patients were aware of the noise generated by the valve, 16% had sleep disturbances and 22% would prefer a more silent valve type. 12 of 38 patients with DE valves and 4 of 36 patients with SJM valves wished to have a less noisy valve type (Chi square p = 0.003). In annoyed patients the valves produced a higher sound amplitude of 49 +/- 8 db(A) as compared to undisturbed patients with 42 +/- 6 db(A) (p = 0.002). The noise level of mechanical heart valves should be considered before selection of a prosthesis, because the metallic click bothers patients and the complaints correlate with measured sound energy.

Adult↗
PubMed1979

Present and future developments in hearing aid design.

Although hearing aids have shown little outward change in the past decade, the development of new components has produced a steady reduction in size and improvement in performance. The near-perfect electret condenser microphone occupies a mere 50 cubic millimeters and its low vibrational sensitivity permits close packing of components without acoustic feedback problems. The integrated circuit packs a hundred components into each cubic millimeter and has allowed the miniaturization of complex aids while simultaneously boosting performance. Integrated circuits will permit future aids to compensate distorted loudness perception as a function of frequency, and extract speech signals buried in noise. These sophisticated, computerized, hearing aids will demand new evaluation and fitting methods and it is the methodology rather than the technology that will pace their development.

Electronics, Medical↗
PubMed1999

[Category loudness scaling to evaluate sound perception in cochlear and retro-cochlear lesions].

Category loudness scaling was used to investigate the loudness perception of 31 patients with a cochlear hearing loss (Group 1) by comparing the results with those found in 15 patients with retro-cochlear hearing loss caused by an acoustic neuroma (Group 2). Narrow-band noise signals at four different frequencies (0.5 to 4.0 kHz) were used. In the cochlear hearing-impaired subjects the slopes of the level-loudness functions tended to increase with increasing hearing loss, indicating positive recruitment, whereas the much shallower slopes associated with retro-cochlear lesions were presumed to reflect negative recruitment. The graphic representation of the iso-loudness functions revealed a different dynamic range between Group 1 and 2 with the ability to discriminate small differences of stimulus levels reduced in the presence of an acoustic neuroma. Category loudness scaling has been shown to be a valuable tool describing the individual perception of sound in a qualitative and quantitative manner. Furthermore, the method can be employed as an indicator of recruitment without any restrictive preconditions. For this reason the categorical loudness scaling can be a desirable method for supplementing the audiological diagnosis of a retro-cochlear hearing impairment through the frequency-specific description of a usable hearing-field and its dynamic range.

Adult↗