Loudness Scaling Research Articles

Functional magnetic resonance imaging measurements of sound-level encoding in the absence of background scanner noise.

Effects of sound level on auditory cortical activation are seen in neuroimaging data. However, factors such as the cortical response to the intense ambient scanner noise and to the bandwidth of the acoustic stimuli will both confound precise quantification and interpretation of such sound-level effects. The present study used temporally "sparse" imaging to reduce effects of scanner noise. To achieve control for stimulus bandwidth, three schemes were compared for sound-level matching across bandwidth: component level, root-mean-square power and loudness. The calculation of the loudness match was based on the model reported by Moore and Glasberg [Acta Acust. 82, 335-345 (1996)]. Ten normally hearing volunteers were scanned using functional magnetic resonance imaging (tMRI) while listening to a 300-Hz tone presented at six different sound levels between 66 and 91 dB SPL and a harmonic-complex tone (F0= 186 Hz) presented at 65 and 85 dB SPL. This range of sound levels encompassed all three bases of sound-level matching. Activation in the superior temporal gyrus, induced by each of the eight tone conditions relative to a quiet baseline condition, was quantified as to extent and magnitude. Sound level had a small, but significant, effect on the extent of activation for the pure tone, but not for the harmonic-complex tone, while it had a significant effect on the response magnitude for both types of stimulus. Response magnitude increased linearly as a function of sound level for the full range of levels for the pure tone. The harmonic-complex tone produced greater activation than the pure tone, irrespective of the matching scheme for sound level, indicating that bandwidth had a greater effect on the pattern of auditory activation than sound level. Nevertheless, when the data were collapsed across stimulus class, extent and magnitude were significantly correlated with the loudness scale (measured in phons), but not with the intensity scale (measured in SPL). We therefore recommend the loudness formula as the most appropriate basis of matching sound level to control for loudness effects when cortical responses to other stimulus attributes, such as stimulus class, are the principal concern.

Psychoacoustic correlates of individual noise sensitivity.

In environmental noise surveys, self-reported noise sensitivity, a stable personality trait covering attitudes toward a wide range of environmental sounds, is a major predictor of individual noise-annoyance reactions. Its relationship to basic measures of auditory functioning, however, has not been systematically explored. Therefore, in the present investigation, a sample of 61 unselected listeners was subjected to a battery of psychoacoustic procedures ranging from threshold determinations to loudness scaling tasks. No significant differences in absolute thresholds, intensity discrimination, simple auditory reaction time, or power-function exponents for loudness emerged, when the sample was split along the median into two groups of "low" vs "high" noise sensitivity on the basis of scores obtained from a psychometrically evaluated questionnaire [Zimmer and Ellermeier, Diagnostica 44, 11-20 (1998)]. Small, but systematic differences were found in verbal loudness estimates, and in ratings of the unpleasantness of natural sounds, thus suggesting that self-reported noise sensitivity captures evaluative rather than sensory aspects of auditory processing.

A "virtual hearing aid" for comparing hearing aids in children: a double-blind crossover study.

In this study, a "virtual hearing aid" was used to compare different types of hearing aids. A digital hearing aid (Oticon DigiFocus Compact) and an analogue, automatic reference hearing aid were compared in a group of 17 schoolchildren (median age: 10 years) with moderate to severe, symmetrical, sensorineural hearing loss. Differences in performance were assessed using routine diagnostic methods (speech recognition performance tests, loudness scaling), subjective assessments (questionnaires) and the "virtual hearing aid". Guaranteeing double-blind testing conditions, the "virtual hearing aid" offers the possibility to directly compare individual in-situ recordings of different hearing aids. In contrast to the clear subjective preferences for the digital hearing aid, we could not obtain any significant results with routine diagnostic methods. Using the "virtual hearing aid", the subjective comparison and speech recognition performance tasks yielded significant differences. The "virtual hearing aid" proved to be suitable for directly comparing different hearing aids under double-blind testing conditions.

Effect of Hearing Loss, Centre Frequency, and Bandwidth on the Shape of Loudness Functions in Categorical Loudness Scaling: Efecto de la hipoacusia, la frecuencia central y el ancho de banda, en la configuración de la funciones de sonoridad en una escala categóries de sonoridad

Loudness functions of narrow-band and broad-band stimuli were measured with eight normally-hearing and eight hearing-impaired listeners using a categorical loudness scaling method. In the normally-hearing listeners, narrow-band stimuli, generally generated loudness functions whose slope increased with increasing level, whereas broad-band stimuli generated more linear loudness functions. These differences can be explained by the level dependence of spectral loudness summation, which is known to be most prominent at moderate levels. In the hearing-impaired listeners, the narrow-band loudness functions generally showed a more linear shape than in the normally-hearing listeners. A consequence of these findings might be that the optimal shape of the input/output curve of a hearing aid is affected not only by the signal power in the respective frequency channels but also by the bandwidth of the input signal. However, there were considerable differences between listeners in both groups regarding the individual shape and absolute position of the loudness functions. Therefore, no normative reference could be extracted that would allow for a quantification of the bandwidth effect on an individual basis.

Empirical evaluation of axioms fundamental to Stevens's ratio-scaling approach: I. Loudness production.

Stevens's direct scaling methods rest on the assumption that subjects are capable of reporting or producing ratios of sensation magnitudes. Only recently, however, did an axiomatization proposed by Narens (1996) specify necessary conditions for this assumption that may be put to an empirical test. In the present investigation, Narens's central axioms of commutativity and multiplicativity were evaluated by having subjects produce loudness ratios. It turned out that the adjustments were consistent with the commutativity condition; multiplicativity (the fact that consecutive doubling and tripling of loudness should be equivalent to making the starting intensity six times as loud), however, was violated in a significant number of cases. According to Narens's (1996) axiomatization, this outcome implies that although in principle a ratio scale of loudness exists, the numbers used by subjects to describe sensation ratios may not be taken at face value.

Testing a new theory of Fechnerian scaling: The case of auditory intensity discrimination

Recently, Dzhafarov and Colonius [Psych. Bull. Rev. 6, 239–268 (1999)] proposed a theory that refines Fechner’s ideas of deriving the perceptual distance between stimuli from discriminability measures in the unidimensional case, and generalizes it to multidimensional stimulus domains. In this theory, the existence of a Fechnerian metric is based on testable assumptions about the shape of the psychometric functions. Thus, ‘‘same–different’’ psychometric functions: (1) have to attain a single minimum at some point; (2) must be locally symmetric around their minima; and (3) must show the same degree of cuspidness, or flatness, along the stimulus continuum. In the present investigation, these assumptions were evaluated experimentally employing acoustical stimuli differing along one stimulus dimension, intensity. In a ‘‘same–different’’ paradigm, using the method of constant stimuli, seven 1000-Hz tones deviating from 0 to 2.1 dB with respect to a standard were presented diotically to five observers. For every participant, psychometric functions were assessed at five hearing levels ranging from 40- to 80-dB HL. The outcome of the ‘‘same–different’’ experiments generally supports the assumptions of the theory. Therefore, data such as these are, in principle, suitable for deriving a global loudness scale from local discriminability measures.

Categorical loudness scaling within the scope of hearing aid management

The loudness perception of patients with hearing aids was measured with a one-stage category loudness scaling procedure. Data were obtained from 102 ears and were studied primarily in older patients who represented the majority of patients with hearing disorders evaluated in our department. In all, 75% of the patients were older than 45 years and had a mean age of 58 years. The reduction of dynamics at high frequencies was considered to be typical for age-related hearing disorders and was easily quantified with loudness scaling. Findings demonstrated that prediction of recruitment was not possible from pure-tone thresholds or even together with uncomfortable loudness levels, since the slopes of the level-loudness functions revealed a high interindividual variability. In contrast, the desired compression ratio can be easily calculated with data from the loudness scaling. In this study the loudness perception of patients with mainly non-linear hearing aids fitted with customary procedures was evaluated. The benefit from the hearing aids was proven with the outcome from the loudness scaling, with testing also allowing for a better fitting of the aids.

Post-operative stapedius reflex tests with simultaneous loudness scaling in patients supplied with cochlear implants.

The estimation of the maximum comfort loudness levels (MCL) by measurements of the electrically elicited stapedius reflex was examined in six experienced cochlear implant users supplied with the COMBI 40 implant system. The stapedius reflex was tested and loudness scaling was performed simultaneously using an up/down stimulation protocol close to the reflex threshold with automated recording of both test procedures. The electrical stapedius reflex threshold (ESRT) and loudness scaling were evaluated separately. Scaling at the reflex threshold ranged between normal and loud. The range of stimulus intensities corresponding to ESRT is much smaller than that at a particular loudness category. The overall correlation between ESRT and MCL was high (r=0.92), with a similar dependence of ESRT and MCL on the channel stimulated. Thus, when the stapedius reflex can be detected post-operatively, the ESRT can be applied successfully for the fitting procedure of the speech processor. Simultaneous loudness scaling during the entire reflex test showed that overstimulation via the implant can be avoided effectively.

Use of auditory field measurement in patients with otosclerosis

Middle ear surgery sometimes leads to unpleasant auditory impressions such as distortion or hyperacusis that cannot be detected by conventional audiometric testing. Sixty-one patients with conductive hearing loss caused by otosclerosis underwent audiological evaluation, which included a questionnaire followed by testing of the audiometric threshold, speech audiometry, and assessment and quantification of loudness perception with a commercial system (WESTRA). This investigation includes the postoperative measurement of hearing improvement and the patients' subjective impressions regarding hearing increase, distortion of speech, and hyperacusis. Hearing improved in 88% of the patients. A quantification of this hearing increase was possible with pure tone audiometry and the Freiburg speech discrimination test. Reduced hearing threshold and lack of improvement in speech discrimination was confirmed by conventional hearing measurements. However, the presence of hyperacusis and distortion of speech could be determined by conventional audiometry in only 50% of cases. It was interesting to note that the subjects who reported speech distortion and hyperacusis in the questionnaire were identified by their increased loudness perception using the categorical loudness scaling. Category loudness scaling appears to be a valuable additional clinical test to characterize postoperative phenomena as distortion of speech and hyperacusis in patients undergoing stapes surgery.

Memory effects in loudness scaling of traffic noise. How overall loudness of short-term and long-term sounds depends on memory.

The influence of cognitive factors such as attention, short-term, and long-term memory on overall loudness of non-steady state sound has not yet been systematically investigated.In this paper, preliminary experimental results are presented, showing how loudness scalings of non-steady state traffic noise depend on memory.

Auditory perception: a new analysis and synthesis

Preface 1. Sound and the auditory system 2. Spatial localization and binaural hearing 3. Perception of acoustic repetition: pitch and infrapitch 4. Judging auditory magnitudes: the Sone scale of loudness and the Mel scale of pitch 5. Perception of acoustic sequences 6. Perceptual restoration of missing sounds 7. Speech 8. The relation of hearing to perception in general References Index.

Loudness Scaling Revisited

The present work was undertaken in an attempt to evaluate whether it is reasonable to expect that categorical loudness scaling can provide useful information for nonlinear hearing aid fitting. Normative data from seven scaling procedures show that the individual procedures relate the perceptual categories differently to sound level and with a substantial between-subject variance. Hearing-impaired data from four studies demonstrate that the inverse slope of the loudness function varies linearly with hearing loss and with a constant variance. In relation to hearing aid fitting, the slope can, in most cases, be predicted from the hearing loss with an accuracy within the range of a normal finetuning. For the fitting of nonlinear hearing aids, the statistical properties of both normal and impaired loudness functions are equally important. The present analysis strongly suggests that categorical loudness scaling cannot, in general, provide significant information for the fitting process.

Development and evaluation of an adaptive loudness scaling procedure

Loudness scaling procedures are used in the diagnostics of hearing impairment to assess the recruitment phenomenon, i.e., the pathological growth of loudness. In these procedures, acoustical stimuli at different levels are presented to the subject and the task is to rate the perceived loudness on a category scale. The aim of this study is the development and evaluation of an adaptive loudness scaling procedure in which the level of the next stimulus is calculated on the basis of the previous trials. Based on empirical results from normal-hearing and hearing-impaired listeners, the procedure was optimized in order to yield minimal test–retest deviations and minimal biases due to range and context effects at minimum measuring time. To achieve these aims, different settings of the following parameters were tested: Number of response alternatives, track length, initial level, adaptive procedure, and parametrization of the loudness function. The best setting was shown to yield an equal distribution of stimulus levels in the full dynamic range of the individual subject with a minimum number of ‘‘inaudible’’ and ‘‘too loud’’ presentations. For each categorial loudness the corresponding stimulus level is estimated with a standard deviation of about 5 dB.

Individual noise sensitivity and performance on psychoacoustic tasks

In environmental noise surveys, self-reported noise sensitivity turned out to be a major predictor of noise-annoyance reactions. Its relationship to basic measures of auditory functioning, however, has not been systematically explored yet. Therefore, in the present investigation, a sample of 61 unselected listeners was subjected to a battery of psychoacoustic laboratory procedures ranging from threshold determinations to loudness scaling tasks. No significant differences in absolute thresholds, intensity discrimination, simple auditory reaction time, or power-function exponents for loudness emerged, when the sample was split along the median into two groups of ‘‘low’’ versus ‘‘high’’ noise sensitivity on the basis of scores obtained from a psychometrically evaluated questionnaire [K. Zimmer and W. Ellermeier, Diagnostica 44, 11–20 (1998)]. Small but systematic differences were found in verbal loudness estimates, and in ratings of the unpleasantness of natural sounds, thus suggesting that self-reported noise sensitivity captures evaluative rather than sensory aspects of auditory processing.

An efficient, adaptive method of measuring loudness growth functions

This paper presents a new categorical loudness scaling procedure that differs from previously published loudness scaling procedures by (i) adaptively selecting a new set of levels for each new sequence, (ii) deriving levels that are equispaced on the loudness scale, and (iii) using a continuous scale with few labels. A major advantage of the adaptive procedure is that the individual dynamic range need not be measured prior to loudness testing. The adaptive procedure proved to be time efficient and to produce complete loudness functions from Not heard to Uncomfortably loud for normal hearing and hearing impaired subjects. The pattern of short-term and long-term reliability was similar to that reported for non-adaptive loudness scaling procedures. Three presentations produced a stable loudness function. Normative curves for one octave babble-noise at six test frequencies are presented and compared to normative data obtained with a selection of published categorical scaling procedures.

Loudness perception is influenced by long-term hearing aid use.

The aim of this study was to explore possible differences in the perception of loudness between long-term hearing aid full-time users and non-users. Categorical loudness scaling using pure-tone stimuli was carried out by hearing-impaired subjects. The mean levels of loudness categories at one frequency (hearing threshold: 50-75 dB HL) in a group of 18 hearing aid users (daily use < or = 15 hours per day) were compared with the corresponding levels found in 18 hearing-impaired non-users with the same distribution of hearing thresholds. The results show that, for hearing losses of 50-75 dB HL, the mean level rated as 'loud' by long-term full-time users of hearing aids is 4.5 dB above the mean level of the corresponding category rated by non-users. This difference is statistically significant (P<0.05). No significant differences were found for the lower categories. Among those subjects who had been wearing hearing aids for at least six months, no significant correlation was found between the levels of the 'loud' category and the length of time that hearing aids had been used.

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.

First audiometric results with the Vibrant soundbridge, a semi-implantable hearing device for sensorineural hearing loss.

The Vibrant soundbridge is a semi-implantable hearing device. The implanted electromagnetic transducer is attached to the incus and it is linked by telemetry to the externally worn audio processor. In Nijmegen, this device has been applied to seven patients with moderate or severe sensorineural hearing loss (PTA between 43 and 71 dB HL) who could not tolerate ear moulds. As the amplification of the device depends on the input level (amplifier with wide dynamic range compression), loudness scaling measurements were performed. The gain as a function of input level was determined from aided and unaided loudness growth curves. The mean gain was 21 dB at an input level of 40 dB SPL. The mean gain decreased to 5 dB at an input level of 90 dB SPL. Measured gain values were lower than target values prescribed by the FIG6 method, mainly however for the low-frequency range and for low-level sounds. It was concluded that this device is very promising for patients who cannot tolerate an ear mould.

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.

The acoustic reflex threshold: not predictive for loudness perception in normally-hearing listeners.

The working hypothesis of an ongoing study is that the quick and reliable procedure of acoustic reflex threshold (ART) determination in conjunction with measurements of HTL may yield accurate estimates of loudness. The aim of this study was to investigate whether differences in loudness in normally-hearing subjects are reflected in the ARTs and to collect normal material with respect to pure-tone elicited ART and loudness categories. Categorical loudness scaling (CLS) and ART measurements were performed at frequencies of 0.5, 1, 2 and 4 kHz in 60 normally-hearing subjects (HTL<20 dB HL, 26 males, 34 females, aged 21-63 years) with no history or sequelae of middle ear disease. Subjects reporting disturbing tinnitus were excluded. The results show that the ART is not a predictor of individual loudness perception for normally-hearing subjects. Using a numerical scale (HTL=0, 'very soft'=5, 'soft'=15, 'OK'=25, 'loud'=35, 'very loud'=45 and 'too loud'=50) loudness for pure tones grows almost linearly at approximately 0.4 arbitrary loudness units per dB below the 'loud' category. Above the 'loud' category the slope is around 1 unit per dB. The median ART was 85 dB HL at frequencies of 0.5, 1, 2 and 4 kHz. No differences in loudness perception across frequencies were found.