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PubMed1998

Sensitivity in changing-loudness aftereffects as indicated by an adjustment procedure: implications regarding mechanisms.

The reduced sensitivity that accompanies some auditory aftereffects has been linked to sensory fatigue. However, changing-loudness aftereffects are unaffected by reduced sensitivity, according to previous evidence from a single-interval forced-choice procedure. That result was confirmed in the present study, in which an adjustment procedure was used to measure changing-loudness aftereffects. In each condition, the listener set the rate of intensity change in test stimuli until they were heard as steady in loudness. The mean of 10 such settings was taken as a measure of the aftereffect's magnitude. The standard deviation of the 10 settings indicated the listener's sensitivity in perceiving changing intensity: The greater the standard deviation, the less the sensitivity. Consistent with previous data, the magnitude of increasing-loudness aftereffects (Experiment 1) and decreasing-loudness aftereffects (Experiment 2) varied according to the adaptation condition, but sensitivity did not. Although sensory fatigue may contribute to aftereffects, the author concluded that reduced sensitivity is not a reflection of sensory fatigue. Instead, it may be explained as a methodological artifact dependent on whether the adapted property is processed by direct or indirect mechanisms. Aftereffects only concern direct mechanisms, but the test stimuli used in their measurement may entail both types of mechanisms: If the measurement entails both types of mechanisms, sensitivity is reduced; if not, sensitivity is unaltered.

Adaptation, Psychological↗
PubMed2000

Hyperacusis: case studies and evaluation of electronic loudness suppression devices as a treatment approach.

Hyperacusis, as defined here, is a relatively rare condition in which the patient, with or without hearing loss, experiences severe loudness discomfort to everyday environmental sound levels. The case studies of 14 patients with severe hyperacusis are described; all wore passive attenuators (earplugs and/or earmuffs) in an attempt to alleviate their discomfort, frequently producing communication difficulties. These subjects were fitted binaurally with experimental electronic loudness suppression devices housed in in-the-ear casings. The devices supplied low-level amplification followed by an extreme form of amplitude compression for moderate or high-level inputs in an attempt to reduce loudness discomfort without reducing audibility. Many of the subjects were found to function with a wider dynamic range with the active devices compared with passive attenuators or the unoccluded ear, and most reported that they benefited from the devices in at least some listening situations.

Adult↗
PubMed2000

Use of the 400 Hz period evoked potential in the prediction of loudness discomfort levels in normal hearing adults.

This study investigated normally-hearing adult subjects to establish whether the 400 Hz Period Evoked Potential (PEP) can be used to predict Loudness Discomfort Level (LDL). Parameter-intensity functions were obtained using the response measures (400 Hz components) of amplitude, phase, magnitude squared coherence (MSC) and phase coherence (PC). The best predictor of the subjective LDL was found to be the gradient of the individual's amplitude-intensity function for significant (MSC > 0.264 and/or PC > 0.525) responses only. In this case 82% are predicted within 10 dB and there is a maximum error of 15 dB.

Adult↗
PubMed2000

Fitting hearing aids to first-time users.

Clinical experience indicates that first-time hearing aid users prefer less gain and lower maximum output levels than experienced users. This hypothesis was tested on 20 subjects being fitted with their first aids. The study was double blinded by using a programmable hearing aid, set to either the standard setting according to the manufacturer's software or to reduced gain and maximum output. Half of the subjects started with one hearing aid and half with the other, changing to the other hearing aid after 3 days trial with each setting. At the end of the study, subjects stated preference in specified situations and overall. No significant differences in APHAB, sound quality, estimated communication ability or perceived loudness scores were seen for the two settings. Nine subjects preferred the standard setting, seven the reduced setting and four were undecided. No correlation could be found between preference and audiological variables.

Acoustic Stimulation↗
PubMed2001

Hearing aid fitting procedures--state-of-the-art and current issues.

The increasing degree of sophistication in hearing aid technology calls for appropriate fitting strategies, as otherwise hearing aid users cannot receive the full benefit from the most modern technological achievements. This paper describes the state of the art in hearing aid fitting procedures and offers a look into possible future developments. Currently, threshold-based fitting formula compete with loudness- and sound-based fitting procedures. Whereas threshold-based approaches are straightforward and timesaving, they do not consider loudness growth and the sound preferences of the listener. On the other hand, loudness- and sound-based procedures do take these aspects into account, but they are time consuming and it is not yet proven that they provide higher benefit for the end user. This may be due to the fact that either there is actually no extra benefit or more likely that the evaluation tools or study designs have to be improved. Concerns about how to fit more advanced future hearing instruments seem to be inappropriate, as an analysis of possible future signal processing algorithms shows that they probably do not need extra fitting to the individual hearing impairment but rather need optimization according to the acoustical environment.

Hearing Aids↗
PubMed2001

A fitting strategy for digital hearing aids based on loudness and sound quality.

In order to find an adequate fitting strategy for digital compression hearing aids a combination of two interactive fitting strategies was developed, one of these based on frequency specifice loudness (ScalAdapt) and the other based on overall loudness and on sound quality (Cambridge Procedure). This new fitting strategy was tested against the sound and overall loudness based strategy and against a prescriptive fitting strategy in a 2-weeks field test with questionnaires and in laboratory measurements, subjectively as well as objectively. With six sensorineural hearing impaired participants no straightforward results were achieved. Additionally, the different testing procedures indicate (in tendency) different fitting strategies to be superior. More subjects will have to be tested and innovative evaluation methods have to be considered.

Acoustic Stimulation↗
PubMed2001

Comparison of two digital hearing instrument fitting strategies.

Two different hearing instrument fitting strategies were compared in the laboratory and in a field test with regard to the benefit for hearing aid users and their satisfaction with the fitting. DSL [input/output (i/o)] fittings based on hearing threshold and uncomfortable levels for the subject were evaluated vs a prescriptive fitting method based on unaided loudness scaling. Twenty-one subjects were fitted diotically with both fitting strategies implemented in a digital hearing instrument (Siemens Prisma). The patients tested both fitting strategies sequentially in a 4 + 4-week field trial using a crossover study design. Speech recognition threshold measurements, sound quality ratings and paired comparisons of sound quality were performed for all conditions (unaided, DSL[i/o] fitting and loudness-based fitting). In addition, subjective benefit and preference were assessed with questionnaires. Speech audiometry did not reveal significant differences between the two fittings. DSL[i/o] fittings showed superior results in most sound quality tests and in the self-assessment of communication abilities while the loudness-based approach was slightly preferred in noisy environments. The results seemed to be influenced by the higher gain predicted by DSL[i/o]. This study provides no evidence that effort spent on loudness scaling leads to improved fitting results.

Audiometry, Speech↗
PubMed2001

Can maximum comfortable loudness levels in hearing impaired listeners be predicted from ipsilateral acoustic reflex thresholds recorded with high frequency probes?

This study was designed to test the effectiveness of the ipsilateral acoustic reflex thresholds measured with low and high frequency probes in predicting the maximum comfortable loudness levels (MaxCLs) in hearing-impaired subjects using recently available sophisticated procedures for acoustic reflex and loudness measures. Loudness growth functions were measured in hearing-impaired subjects at .5, 1 and 2 kHz using a computerized procedure. The maximum level among those sound pressure levels judged as 'comfortable' was designated as the MaxCL. Acoustic reflex thresholds were measured for .5, 1 and 2 kHz activator signals using 226, 678 and 1000 Hz probes. Regression analyses suggested that acoustic reflex thresholds recorded with the 678 and 1000 Hz probes could provide an objective estimate of the MaxCLs for 1 and 2 kHz. Thus, acoustic reflex thresholds may be useful in fitting hearing aids for those subjects in whom reliable measures of MaxCLs cannot be obtained.

Adult↗
PubMed1998

Clinical evaluation of a portable digital hearing aid with narrow-band loudness compensation.

A new portable digital hearing aid referred to as CLAIDHA (Compensate for Loudness by Analyzing Input-signal Digital Hearing Aid), which employs frequency-dependent amplitude compression based on narrow-band loudness compensation, was clinically evaluated in 159 subjects with hearing loss. The results of speech tests revealed better intelligibility compared with the subject's own hearing aids; the advantage of using CLAIDHA in daily life was also indicated by the results of a questionnaire completed by the subjects. In about 64% of the subjects with a flat, gradually sloping type of hearing loss, CLAIDHA was satisfactorily adopted for daily use. However, in the subjects with a steeply sloping type of hearing loss and subjects with losses mainly at high and low frequencies, with near-normal mid-frequency hearing. this loudness compensation scheme seems to be slightly less effective.

Aged↗
PubMed1998

Long-term test-retest reliability of category loudness scaling in normal-hearing subjects using pure-tone stimuli.

The present study investigates the test-retest reliability of category loudness scaling with pure tones for each of the scaling categories: 'very soft', 'soft', 'OK', 'loud', 'very loud' and 'too loud' at the audiometric frequencies 0.5, 1 kHz, 2 kHz and 4 kHz. Category loudness scaling at two sessions separated by between 1 and 4 weeks was obtained from 16 normal-hearing subjects who all had normal otoscopy, present acoustic reflexes at audiometric frequencies 0.5-4 kHz and middle ear pressure within +/-50 daPa. Intra-subject between-session reliability was found not to be frequency dependent, and comparison with other studies revealed that reliability is not dependent on the applied stimulus signal. Test-retest reliability varied between the different categories: In the categories 'very soft', 'loud', 'very loud' and 'too loud' the test reliability is in the same range as found for hearing thresholds determination, whereas for the 'soft' and 'OK' categories it is poorer. The greater uncertainty for intermediate levels should be considered when using category loudness scaling, e.g. for calculating hearing aid parameters.

Adult↗
PubMed1999

Hypersensitivity to sound--questionnaire data, audiometry and classification.

This study included consecutive case histories and audiometry of 100 patients with hypersensitivity to sounds. There are several different conditions with the symptom of hypersensitivity to sounds. Hyperacusis is one of those and is seldom described in the literature. The term hyperacusis is often used synonymously with hypersensitivity to sound. We propose that there is a specific condition that could be termed hyperacusis. Hyperacusis is often elicited by loud sounds or by a number of other traumata or diseases. It is not typical of occupational noise exposure (with the exception of exposure to music). The typical patient is relatively young, the mean age being approximately 10 years less than for a population of patients with tinnitus or noise-induced hearing loss. In addition to hypersensitivity to sound, the patients often suffer from tinnitus (86%). Sounds are frequently painful and exposure to loud sounds worsens the condition for some time. The patients often have headaches. Pure tone audiograms show normal hearing or a slight high tone loss. The uncomfortable loudness level is markedly decreased, mostly less than 90 dB HL. Patients with hyperacusis may also be divided into those hypersensitive to the loudness of sounds with a decreased pure tone uncomfortable loudness level and those hypersensitive to certain specific sounds irrespective of loudness showing relatively high pure tone uncomfortable loudness levels and decreased uncomfortable loudness levels to specific sounds. With a careful history other conditions with the symptom of hypersensitivity to sound can be excluded.

Adolescent↗
PubMedDate not supplied

Contemporary issues in audiology: a hearing scientist's perspective.

Audiology has developed significantly over the last 30 years leading to better identification and assessment of hearing loss and better habilitation services for both children and adults with congenital or acquired deafness. Advancement in the profession and its services has been largely dependent on the technological development of key methodologies such as the auditory brainstem response and otoacoustic emissions. These methodologies have been used for the identification and assessment of the severity of hearing loss. As a result, these methodologies have underpinned the emergence of service development initiatives such as hearing screening and provision of hearing aids, particularly for newborn babies and young children. This review identifies, describes and evaluates the key methodologies and services involved and presents a hearing scientist's perspective on the developments to date. The aim is to provide state-of-the-art information to those working with children and adults with communication disorders, particularly speech and language therapists.

Adult↗
PubMed1989

Psychometric functions for the discrimination of differences in intensity of Gaussian noise.

A new theory of sensory functioning by Laming predicts how the shape of the psychometric function depends on the context in which a signal is presented. The discrimination of intensities of noise was therefore studied with four different stimulus configurations. In one, observers discriminated between two separate noise samples that differed in intensity. In accordance with the theory, a normal probability integral provided a better fit to each observer's data than either of two other functions: a normal integral with respect to the square of the difference, or a normal integral with respect to the fourth power of the difference. In a second task, observers detected an increment in a continuous noise. For eight out of nine sets of data, a square-law function provided a better fit than either a normal integral or fourth-power function. A third task asked observers to decide which of two noises was amplitude modulated. The predicted square-law function provided the best fit for four out of five observers. In a fourth task, one observer detected an interval of amplitude modulation in a continuous noise. As predicted by the theory, a fourth-power function provided the best fit. In addition, Weber fractions for difference discriminations decreased approximately with the square root of sample duration for durations up to 300 msec, whereas Weber fractions for increment detections decreased approximately directly with duration for durations up to 100 msec. The results are usually in qualitative agreement with the theory and often in quantitative agreement as well.

Adult↗
PubMed1991

Spectral, intensive, and temporal factors influencing overshoot.

Threshold was measured for a 10-msec, 4.0-kHz signal presented near the onset or in the temporal centre of a 400-msec noise masker. Overshoot, the difference (in dB) between these two thresholds, was seen only for masker bandwidths wider than a critical band. The threshold near masker onset, and hence overshoot, could be reduced by the presence of an additional noise that was presented continuously or gated on and off prior to masker onset. The spectral, intensive, and temporal properties of this effect were studied. When the additional noise was continuous and either bandpass filtered with a variable bandwidth or notch filtered with a variable notchwidth, the results indicated that energy both near and remote from the signal frequency contributed to the reduction in overshoot. The effect of this additional noise was highly dependent upon its relative level. When the additional noise was 400 msec in duration and the delay between its offset and the onset of the masker was varied, overshoot "recovered" to its maximum value within about 50 msec. Finally, as the duration of the additional noise was varied from 3 to 400 msec while the time between its offset and masker onset was fixed, the reduction in overshoot was virtually complete for durations of about 25-50 msec. The results are consistent with the notion that overshoot at least partly reflects peripheral adaptation, and that this adaptation is not restricted to the signal frequency channel but, rather, extends in both directions over several channels.

Adult↗
PubMed1991

Effects of phase changes in low-numbered harmonics on the internal representation of complex sounds.

A series of experiments investigated the effect of phase changes in low-numbered single harmonics in target sounds that were either synthesized steady-state vowels fo periodic signals having only a single formant. A matching procedure was sued in which subjects selected a sound along a continuum differing in first formant frequency in order to get the best match with the target sound; perceptual effects of the phase manipulations in the target were detected as a change in the matched first formant frequency. Stimuli had to contain at least three harmonics to produce the effect, but id did not require a particular starting phase of the components. A suppression phenomenon is discussed, in which phase changes alter the phase-locking characteristics of auditory fibres tuned to low-numbered harmonics.

Adult↗
PubMed1991

Spectral weights and the profile bowl.

In these experiments, listeners detected changes in the shape of a complex spectrum that varied in overall level. With multicomponent complexes, a typical finding is that the listeners were more sensitive to changes made in the middle components of the spectrum than to changes made at either edge. We used a technique developed by Berg (1989) to estimate the weight listeners attached to the different components of the spectrum in making these judgements. For reasons not understood, the pattern of spectral weights was nearly optimum for a change made in the middle component of the spectrum and much poorer when the change occurred at either edge.

Attention↗
PubMed1991

The detection of a tone added to a narrow band of noise: the energy model revisited.

In an effort to determine whether cues related to changes in energy contribute to the detection of a tone added to a narrow band of noise, we examined the effect of level variation on detection thresholds. In the first experiment, the level of each waveform was randomly varied on each presentation. Level variation had only marginal effects on performance. In addition, detection thresholds were obtained using bands of noise with equal energy across intervals. Neither increasing nor decreasing the variance of the noise-alone and tone-plus-noise energy difference distributions altered the detectability of a tone added to noise. Thus, the changes in energy that are concomitant with the addition of the tone are not the sole cue for the detection of the tone. In a second experiment, three psychometric functions were measured. One function was determined using no level variation, one was measured in the presence of level variation, and one was measured in the context of level variation, but for trials without level variation. The context of level variation slightly reduced detectability. In a third experiment, we compared detectability in three conditions: no level variation, across-trial level variation, and across-interval level variation. The thresholds obtained in the absence of level variation were superior to those measured in the presence of level variation, regardless of the manner in which the level variation was incorporated.

Attention↗
PubMed1991

Lateralization of very-short-duration tone pulses of low and high frequencies.

The position and image-width of the simultaneous images produced by very short tone pulses were measured as a function of interaural time difference (ITD) at both low- (250 and 800 Hz) and high- (2500 and 8000 Hz) frequencies using a direct-estimation technique. Primary images are lateralized towards the ear receiving the leading stimulus. At low frequencies image position is proportional to interaural phase-difference (IPD) below 90 degrees and remains at the lead-ear for larger values. At high frequencies images are reported is proportional to ITD up to 500-1000 microseconds. Secondary images are reported on the opposite side of the head for IPDs greater than 180 degrees at low frequencies, and at ITDs greater than 500 microseconds at high frequencies. Image width is approximately constant for all ITDs and both images at a given frequency, but becomes more compact as frequency increases. The data are discussed in terms of onset cues and stimulus fine-structure cues. The best explanation is in terms of an onset mechanism, but one that is calibrated in terms of IPD at low frequencies. The existence of double images is explained in terms of a breakdown in the mechanism determining fusion.

Adult↗