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PubMedDate not supplied

Effect of signal duration on categorical loudness scaling in normal and in hearing-impaired listeners.

The present study sought to determine whether the duration of white-noise bursts affects their loudness category rating in the same way for hearing-impaired as for normally-hearing subjects. Twelve normally-hearing and 12 hearing-impaired subjects took part. Categorical loudness growth functions were obtained for 16.25 ms, 32.5 ms, 75 ms, 150 ms and 300 ms white noise bursts. Temporal integration of loudness was defined as the intensity difference needed for stimuli of different durations to result in identical category ratings. In normally-hearing subjects, temporal integration of loudness occurred mainly with the short-duration (16.25 ms and 32.5 ms) stimuli, whereas it was found with almost every stimulus duration in hearing-impaired subjects. In other words, temporal integration of loudness between 16.25 ms and 300 ms stimulus duration was greater in hearing-impaired listeners and there was a difference between normal and hearing-impaired subjects regarding change in loudness perception with stimulus duration. Consequently, the use of fixed-duration stimuli hinders loudness normalization.

Adolescent↗
PubMed1997

Clinical evaluation of three different loudness scaling protocols.

Loudness scaling has recently attracted much attention as a valuable clinical tool for acquiring reliable knowledge about loudness perception. This information can be used for diagnostic and rehabilitative purposes. In this study a loudness scaling module implemented in a new PC-based audiological test system was comprehensively tested. The system has proven to be a reliable and useful tool in a clinical environment. The described 'Default' loudness scaling protocol seems to represent an appropriate set of parameters. A comparison between this protocol and two other protocols available for clinical use indicates that the 'Default' protocol presents the same consistency of subject response as the 'IHAFF' protocol, and a better consistency than the 'LGOB' protocol. Regarding time consumption, the 'Default' protocol is superior to the 'IHAFF' protocol and comparable to the 'LGOB' protocol.

Audiometry, Pure-Tone↗
PubMed2001

Modeling temporal and compressive properties of the normal and impaired auditory system.

Three modifications of a psychoacoustically and physiologically motivated processing model [Dau et al., J. Acoust. Soc. Am. 102 (1997a) 2892-2905] are presented and tested. The modifications aim at simulating sensorineural hearing loss and incorporate a level-dependent peripheral compression whose properties are affected by hearing impairment. Model 1 realizes this difference by introducing for impaired listeners an instantaneous level-dependent expansion prior to the adaptation stage of the model. Model 2 and Model 3 realize a level-dependent compression with time constants of 5 and 15 ms, respectively, for normal hearing and a reduced compression for impaired hearing. In Model 2, the compression occurs after the envelope extraction stage, while in Model 3, envelope extraction follows compression. All models account to a similar extent for the recruitment phenomenon measured with narrow-band stimuli and for forward-masking data of normal-hearing and hearing-impaired subjects using a 20-ms, 2-kHz tone signal and a 1-kHz-wide bandpass noise masker centered at 2 kHz. A clear difference between the different models occurs for the processing of temporally fluctuating stimuli. A modulation-rate-independent increase in modulation-response level for simulating impaired hearing is only predicted by Model 1 while the other two models realize a modulation-rate-dependent increase. Hence, the predictions of Model 2 and Model 3 are in conflict with the results of modulation-matching experiments reported in the literature. It is concluded that key properties of sensorineural hearing loss (altered loudness perception, reduced dynamic range, normal temporal properties but prolonged forward-masking effects) can effectively be modeled by incorporating a fast-acting expansion within the current processing model prior to the nonlinear adaptation stage. Based on these findings, a model of both normal and impaired hearing is proposed which incorporates a fast-acting compressive nonlinearity, representing the cochlear nonlinearity (which is reduced in impaired listeners), followed by an instantaneous expansion and the nonlinear adaptation stage which represent aspects of the retro-cochlear information processing in the auditory system.

Auditory Pathways↗
PubMed1991

Slippery context effect and critical bands.

This article explored the slippery context effect: When Ss judge the loudness of tones that differ in sound frequency as well as intensity, stimulus context (relative intensity levels at the 2 frequencies) can strongly influence the levels that are judged equally loud. It is shown that the size of the slippery context effect depends on the frequency difference between the tones: Small frequency differences (less than a critical bandwidth) produced essentially no slippery effect; much larger differences produced substantial effects. These results are consistent with a model postulating the existence of a central attentional or preattentive "filter-like" process whose weighting coefficients represent the size of the absolute as opposed to the relative (contextual) component of loudness perception and judgment.

Adult↗
PubMed1993

Contextual processing of multidimensional and unidimensional auditory stimuli.

Stimulus context (the distribution of stimulus values) can strongly affect both perception and judgment. In 14 experiments, the method of magnitude estimation revealed 2 fundamentally different kinds of context effect in loudness. An assimilative effect dominated when stimuli varied unidimensionally (in intensity only). But a contrasting, or adaptation-like, effect dominated when stimuli varied multidimensionally (in frequency and intensity). In Experiment 15, direct loudness comparison revealed a potent, adaptational process specific to the signal frequency. Taken together, these and other results are compatible with the view that loudness perception and judgment reflect the net outcome of 2 different contextual processes: a relatively early (though probably not peripheral) process of perceptual adaptation and a later process of response-dependent assimilation.

Adult↗
PubMed1990

Loudness growth in 1/2-octave bands (LGOB)--a procedure for the assessment of loudness.

In this paper, a method that has been developed for the assessment and quantification of loudness perception in normal-hearing and hearing-impaired persons is described. The method has been named LGOB, which stands for loudness growth in 1/2-octave bands. The method uses 1/2-octave bands of noise, centered at 0.25, 0.5, 1.0, 2.0, and 4.0 kHz, with subjective levels between a subject's threshold of hearing and the "too loud" level. The noise bands are presented to the subject, randomized over frequency and level, and the subject is asked to respond with a loudness rating (one of: VERY SOFT, SOFT, OK, LOUD, VERY LOUD, TOO LOUD). Subject responses (normal and hearing-impaired) are then compared to the average responses of a group of normal-hearing subjects. This procedure allows one to estimate the subject's loudness growth relative to normals, as a function of frequency and level. The results may be displayed either as isoloudness contours or as recruitment curves. In its present form, the measurements take less than 30 min. The signal presentation and analysis is done using a PC and a PC plug-in board having a digital to analog converter.

Adult↗
PubMed1997

Electrical middle ear muscle reflex: use in cochlear implant programming.

Programming of multichannel cochlear implants (CIs) requires subjective responses to a series of sophisticated psychophysical percepts. It is often difficult for young prelinguistically deaf children to provide adequate responses for device fitting. This is especially true in setting levels of maximum comfortable loudness, whereby failure to indicate growth of loudness may result in elevation of stimulus levels to the threshold of pain. The acoustic or stapedial muscle reflex has been used previously to provide objective confirmation of acoustic stimulation, and there have been attempts to use the reflex in hearing aid fitting. It has also been suggested that electrically elicited middle ear muscle reflexes (eMEMR) may have applicability in confirming and quantifying electrical stimulation through a CI. To assess the relationship between eMEMR characteristics and levels of loudness perception with CIs, determine reliability of the response, and investigate potential use of eMEMR in CI programming, 25 postlinguistically deafened adult CI users were evaluated. Reflexes have also been attempted on 40 children, with responses present in 31 (71%). Comfort levels predicted by eMEMR were highly correlated with those obtained through subjective judgments in the adult subjects. The eMEMR provides an objective, accurate, and rapid method of estimating maximum comfortable loudness levels, which may be useful in the initial programming of young implant recipients.

Acoustic Stimulation↗
PubMed1999

Electrocochleographic documentation of temporal findings of speech perception in normal and hearing-impaired individuals.

Compound action potentials (CAPs) evoked by the short Japanese syllables /a/ and /ka/ were recorded by extratympanic electrocochleography in 17 subjects with normal hearing (17 ears) and 34 patients with sensorineural hearing losses (35 ears) to investigate the temporal aspects of speech coding for perception. In normal ears, three characteristics were found common to the temporal patterns of all CAPs: (1) a prominent CAP at the beginning of both stimuli; (2) periodic CAPs with the same interval as the pitch period through the vowel part of both stimuli; (3) absence of a prominent CAP at the onset of voice. These characteristics may help to produce consonant recognition. Among the subjects with sensorineural hearing loss, some ears showed the following two characteristics different from those with normal hearing: (1) a significantly lower CAP at the onset of both stimuli than in those with normal hearing; (2) decay of CAPs during the voiced part. These findings may result in abnormal loudness perception in sensorineural hearing loss as produced by loudness recruitment and pathological adaptation. Such different temporal patterns of CAPs may have an adverse influence on the speech discrimination of patients with sensorineural hearing impairments.

Acoustic Stimulation↗
PubMed1999

Temporal loudness integration and spectral loudness summation in normal-hearing and hearing-impaired listeners.

The aim of this study was to test for differences between normal-hearing and hearing-impaired listeners regarding two fundamental aspects of intensity perception: loudness integration and loudness summation. Loudness functions for three different stimuli were measured using categorical loudness scaling in 8 normal-hearing and 12 hearing-impaired subjects. The results indicated that temporal loudness integration, defined as the difference in SPL between 16.25-ms and 300-ms noise bursts of equal loudness, was larger in the hearing-impaired than in the normal-hearing listeners. Loudness summation, defined as the difference in SPL between a 300-ms, 1,600-Hz tone pip and a white noise burst of the same duration and loudness, did not differ between the two groups. Implications of these results for hearing aid fitting strategies based on loudness normalization are discussed.

Adult↗
PubMed1990

Loudness and auditory brain stem evoked response.

Auditory brain stem responses evoked with click stimuli of varying repetition rates (11, 31, 51, and 91 clicks/sec) and intensities but judged as being equally loud as three reference loudness levels (90, 80, and 70 phons) were examined in normal-hearing listeners. Analysis of wave component latencies and amplitudes indicated that loudness level changes are reflected in the brain stem response. However, the combined influence of stimulus rate and intensity was greater than that of perceived loudness level. It was concluded that the auditory brain stem response does not provide a direct link to loudness perception.

Adult↗
PubMed2006

Indication for the need of flexible and frequency specific mapping functions in cochlear implant speech processors.

Categorical loudness scaling of electric and acoustic stimuli was performed in cochlear implant (CI) recipients equipped with Nucleus systems in order to achieve a normal loudness perception in the whole dynamic range of acoustic input. For each electrode, the lower and upper limits of electric stimulus were defined by the values corresponding to "very soft" and "too loud". Within this dynamic range, the stimulus strength intervals associated to the verbal categories "soft", "medium", "loud" and "very loud" were determined. The same loudness categories were used for the scaling of acoustic stimuli. From both scaling experiments, the transduction of the CI system can be assessed and the parameters of the individual mapping function yielding a normal loudness growth can be derived. Deviations from optimum mapping can be corrected at least partially by manipulating the parameters of the mapping function. In many cases, however, one mapping function is not sufficient for all channels. The results argue in favour of the development of flexible and channel-specific mapping function parameters in future CI systems.

Cochlear Implants↗
PubMedDate not supplied

The relationship between the acoustic reflex threshold and levels of loudness categories in hearing-impaired listeners.

When applied as a tool for hearing aid fitting, categorical loudness scaling (CLS) is time consuming and not feasible in all subjects. It is therefore desirable to use objective measures for accurate prediction of loudness categories among hearing-impaired individuals. The present study aimed at exploring whether loudness perception at the ART is constant with varying hearing threshold. Seventy-five subjects with various degrees of hearing impairment, measurable acoustic reflex and normal middle ear function participated. The HTLs, ARTs and the levels of six loudness categories at frequencies 0.5, 1, 2 and 4 kHz were determined for all subjects. Loudness at the ART was found to be correlated with the amount of hearing loss. On the basis of these results, it is concluded that the ART cannot be used for accurate estimation of loudness in hearing-impaired subjects.

Adult↗
PubMed2002

Intensity-related performances are modified by long-term hearing aid use: a functional plasticity?

It is now well established that the adult central nervous system can reorganize following various environmental changes. In particular, it has been hypothesized that auditory rehabilitation of sensorineural hearing-impaired adults may involve functional plasticity. The present study sought to compare intensity-related performance between two groups of subjects paired for age, gender and absolute thresholds in both ears. One group comprised long-term binaural hearing aid (HA) users and the other non-HA users. The effect of HA use was measured in two intensity tasks, a discrimination-limen-for-intensity task (DLI) and a loudness-scaling task. Results indicated that significant differences exist in loudness perception between long-term HA users and non-HA users, the latter rating intensity as louder than the former. Concerning intensity discrimination performance, a statistical tendency to lower, i.e. better, DLIs in long-term than in non-HA users was revealed. Moreover, significant differences between ears were observed in the loudness-scaling task, with the right ear showing greater inter-group difference than the left ear. This additional result points to a lateralization of the acclimatization effect. Finally, this study suggests significant perceptual modification and thus a possible functional plasticity entailed by HA use.

Adaptation, Physiological↗
PubMedDate not supplied

Auditory perceptual and visual-spatial characteristics of gaze-evoked tinnitus.

Auditory perceptual and visual-spatial characteristics of subjective tinnitus evoked by eye gaze were studied in two adult human subjects. This uncommon form of tinnitus occurred approximately 4-6 weeks following neurosurgery for gross total excision of space-occupying lesions of the cerebellopontine angle and hearing was lost in the operated ear. In both cases, the gaze-evoked tinnitus was characterized as being tonal in nature, with pitch and loudness percepts remaining constant as long as the same horizontal or vertical eye directions were maintained. Tinnitus was absent when the eyes were in a neutral head-referenced position with subjects looking straight ahead. The results and implications of ophthalmological, standard and modified visual-field assessment, pure-tone audiometric assessment, spontaneous otoacoustic emission testing and detailed psychophysical assessment of pitch and loudness are discussed.

Audiometry, Pure-Tone↗
PubMed2002

[Effect of information about hearing damage caused by loud music. For adolescents the music in discoteques is too loud despite loudness limits].

BACKGROUND: Information campaigns are regarded useful to prevent adolescents from hearing-damage due to loud music. This study examined whether adolescents who are informed on the risk of a hearing-damage, exhibit preventive behavior when attending discotheques. METHOD: 253 pupils (age 14 to 19 years) were interviewed about their disco attending habits and about their information on the risk associated with listening to loud music. RESULTS: About 85% of the sample were informed about the risk. Informed and uninformed pupils did not significantly differ in the frequency of disco attendance nor in the frequency of using ear-plugs. However, significantly more informed pupils experienced disco music as too loud (p < 0.05). CONCLUSIONS: Information influences the subjective appraisal of loudness perception, but has little effect on preventive behavior. Instead, experimental forms of educational campaigns may be more effective. Additional provisions (lowering sound levels in discotheques) are necessary.

Adolescent↗
PubMed1998

Basilar membrane nonlinearity and loudness.

Loudness matching functions for tones for persons with one shifted-threshold ear (hearing loss and noise-shifted thresholds) and one ear within normal limits were used to derive the presumed basilar membrane (BM) input-output (I/O) function in a normal ear. The comparison was made by assuming that the BM I/O function for the ear with the cochlear threshold shift has a slope of one (a linearized cochlea). The function for the normal ear was derived from the loudness matching function based on this assumption. Comparisons were made for archival basilar membrane data [M. A. Ruggero, N. C. Rich, A. Recio, S. S. Narayan, and L. Robles, J. Acoust. Soc. Am. 101, 2151-2163 (1997)] for chinchilla and archival loudness matches for long-duration tones for persons with various degrees of cochlear hearing loss [F. Miskolczy-Fodor, J. Acoust Soc. Am. 32, 486-492 (1960)]. Comparisons were made also between BM I/O functions and ones derived from loudness matches for persons with unilateral hearing loss simulated by broadband noise. The results show a close resemblance between the basilar membrane I/O function and the function derived from loudness matches for long-duration tones, even though the comparison was between human and chinchilla data. As the degree of threshold shift increases from 40 to 80 dB, the derived BM I/O functions become shallower, with slopes for losses of 60 dB or more falling in the range of values reported for physiological data. Additional measures with short-duration tones in noise show that the slope of the loudness function and the slope of the derived basilar membrane I/O function are associated with the behavioral threshold for the tone. The results for long-duration tones suggest a correspondence between BM displacement and loudness perception in cases of recruitment, but the relation between the degree of loss and the amount of BM compression and the relation between signal duration and compression suggests that other factors, such as the neural population response, may play a role.

Adult↗
PubMed2004

How cochlear implants encode speech.

PURPOSE OF REVIEW: This review summarizes the history of cochlear implant signal processing and provides the rationale underlying current approaches. Present strategies are explained and recent research findings are summarized. It is suggested how these results may drive future advancements in signal processing. RECENT FINDINGS: Substantial advances have been made in our understanding of the spectral and temporal cues necessary for cochlear implant recipients to perceive music, speech in noise, and interaural timing. It is clear that higher levels of both spectral and temporal resolution, as well as better loudness and pitch coding are necessary for higher levels of performance. These factors are highly interrelated, however, and are beneficial for differing aspects of hearing. Signal processing algorithms incorporating these findings are under active development and some are currently undergoing clinical investigation. SUMMARY: Current implant devices, and those soon to be available, have substantial untapped potential to improve the auditory experience of their recipients. It is likely that in the near future, recent findings on pitch and loudness perception, as well as techniques to better emulate the normal functions of the cochlea will result in much higher levels of prosthetic hearing fidelity than are possible today. As the performance of these remarkable devices continues to improve, the population of hearing-impaired individuals who can benefit from implantation is likely to increase significantly.

Cochlear Implantation↗
PubMed1996

Adaptive fitting of hearing instruments by category loudness scaling (ScalAdapt).

The introduction of programmable as well as non-linear hearing instruments has shown that audiogram-based fitting procedures are inappropriate for meeting the individual needs of hearing aid users with sensorineural loss. Particularly the present and future development of hearing instruments with advanced analog and digital signal processing requires suitable fitting procedures. In this context, we developed an adaptive fitting strategy (ScalAdapt) using category loudness scaling. In this paper the procedure is described and tested using programmable 3-channel AGC instruments. However, it can be modified for any other hearing aid design. The underlying idea is to normalize the aided loudness perception for two input levels, one around the most comfortable level (MCL) and the other just below the uncomfortable level (UCL), as anchor points in each channel by interactive fine-tuning of the fitting parameters (channel gain, compression onset, compression ratio, etc.). The benefits of ScalAdapt have been evaluated by a field test study in 17 experienced hearing aid users. The results showed that ScalAdapt provides consistently higher objective (speech recognition in noise) and subjective benefits (self-assessment inventory) than for instance NAL-based fittings.

Hearing Aids↗