Loudness Measurements Research Articles

An introduction to induced loudness reduction

Induced loudness reduction (ILR) is a phenomenon by which a preceding higher-level tone (an inducer tone) reduces the loudness of a lower-level tone (a test tone). The strength of this effect depends on a number of parameters, reviewed here. Some of the implications of ILR on loudness data are presented via the analysis of several studies in which ILR likely resulted in otherwise unexplained biases in data sets. These results serve as examples of the pervasiveness of ILR in loudness measurements and indicate that it is necessary to consider ILR when designing any psychoacoustical experiment in which level varies.

Short-Term and Long-Term Hearing Aid Benefit and User Satisfaction: A Comparison between Two Fitting Protocols

Currently published hearing aid fitting protocols recommend speech-in-noise testing and loudness measures, but it remains unclear how these measures affect hearing aid benefit and user satisfaction. This study compared two protocols in their effects on benefit and satisfaction. Protocol A included an electroacoustic analysis, real-ear measures, and hearing aid adjustments based on users' comments. Protocol B included all of Protocol A and a speech-in-noise test, loudness discomfort levels, and aided loudness. Thirty-two participants completed the Abbreviated Profile of Hearing Aid Benefit (APHAB) and the Satisfaction with Amplification in Daily Life (SADL) at 45 days and three months post-initial fitting. Fewer hearing aid adjustments were made to the hearing aids for participants fitted with Protocol B than participants fitted with Protocol A, but final gains were similar for both groups. Although similar APHAB scores were obtained for both protocols, SADL scores decreased between 45 days and three months for Protocol A.

Hearing Aid Maximum Output and Loudness Discomfort: Are Unaided Loudness Measures Needed?

The purpose of this study was to evaluate a clinical protocol for setting hearing aid maximum output (MPO) in adult users. The protocol consisted of matching prescriptive targets for MPO followed by aided loudness validation and adjustment. Twenty-eight adults fit with multichannel hearing aids during the previous two years were recalled for unaided loudness measures. During the recall visit, unaided frequency-specific loudness discomfort levels were measured for frequencies between 250 and 3000 Hz. These values were converted to real-ear levels by adding individually measured real-ear dial differences. Real-ear saturation responses (RESR) were measured using a 90 dB pure-tone sweep and compared to the real-ear loudness discomfort levels. All participants completed the APHAB Aversiveness scale and Munro-Patel loudness questionnaire. A subset of participants (n = 20) completed the Profile of Aided Loudness. The average RESR-UCL difference was -5.7 dB, and the maximum difference was 15 dB. For all but one participant, the average RESR values (.5-3 kHz) were either less than or no more than 5 dB above the LDLs, and the aided APHAB Aversiveness scores were below the 80th percentile. There were no significant correlations between the scores on the loudness questionnaires and the differences between RESR and LDL values. Results suggest that unaided LDL measures may be redundant if aided loudness validation measures are completed.

Identification variability as a measure of loudness: An application to gender differences.

It is well known that discrimination response variability increases with stimulus intensity, closely related to Weber's Law. It is also an axiom that sensation magnitude increases with stimulus intensity. Following earlier researchers such as Thurstone, Garner, and Durlach and Braida, we explored a new method of exploiting these relationships to estimate the power function exponent relating sound pressure level to loudness, using the accuracy with which listeners could identify the intensity of pure tones. The log standard deviation of the normally distributed identification errors increases linearly with stimulus range in decibels, and the slope, a, of the regression is proportional to the loudness exponent, n. Interestingly, in a demonstration experiment, the loudness exponent estimated in this way is greater for females than for males.

Predicting changes in breathiness resulting from variations in aspiration noise and open quotient using a loudness model

Previous studies have reported that increases in high-frequency aspiration noise (AH) and open quotient (OQ) are correlated with an increase in the perception of breathiness in vowels [Klatt and Klatt, J. Acoust. Soc. Am. 87, 820–857 (1990)]. However, a system based on psychoacoustic loudness models has been shown to predict the level of breathiness in vowels to a greater extent than AH and OQ themselves [Shrivastav and Sapienza, J. Acoust. Soc. Am. 114, 2217–2224 (2003)]. The goal of this experiment was to verify the significance of AH and OQ in the perception of breathiness and to determine how each of these influences the output of the loudness model, individually and in combination. Ten vowels, five male and five female, were synthesized using a Klatt synthesizer. Each vowel was used to generate three continua varying in terms of their OQ and/or AH. Ten listeners rated breathiness for each continuum using a magnitude estimation task. Results show that normalized partial loudness as well as the loudness of aspiration noise predicted changes in breathiness resulting from an increase in AH. Increase in OQ resulted in very small changes in perceived breathiness, resulting in poor correlation with loudness measures. [Research supported by NIH/R21DC006690.]

Loudness of brief tones measured by magnitude estimation and loudness matching

McFadden [J. Acoust. Soc. Am. 57, 702-704 (1975)] questioned the accuracy and reliability of magnitude estimation for measuring loudness of tones that vary both in duration and level, whereas Stevens and Hall [Percept. Psychophys. 1, 319-327 (1966)] reported reasonable group data. To gain insight into this discrepancy, the present study compares loudness measures for 5- and 200-ms tones using magnitude estimation and equal-loudness matches from the same listeners. Results indicate that both procedures provide rapid and accurate assessments of group loudness functions for brief tones, but may not be reliable enough to reveal specific characteristics of loudness in individual listeners.

Effects of Test Order on Most Comfortable and Uncomfortable Loudness Levels for Speech

This study examined test-order effects on most comfortable loudness (MCL) and uncomfortable loudness (UCL) levels for spondaic words in 2 groups of 30 normal hearing listeners each. For Group 1, MCL was measured first, followed by UCL. For Group 2, UCL was measured first, and then MCL. A retest was conducted for both groups. Results showed that MCL was significantly elevated for Group 2, but not for Group 1. There was no effect on UCL for either group. In a follow-up experiment, the magnitude of the test-order effect on MCL increased significantly when MCL measurements followed UCL measurements closely in time. These results argue for management of the ordering and temporal spacing of MCL and UCL testing in clinical loudness measurements.

Toward a Battery of Behavioral and Objective Measures to Achieve Optimal Cochlear Implant Stimulation Levels in Children

Children require audible and comfortable stimulation from their cochlear implants immediately after device activation. To accomplish this, a battery of objective measures may be needed that could include the electrically evoked stapedius reflex (ESR), compound action potential from the auditory nerve (ECAP), and/or auditory brain stem response (EABR). In the present study, the following specific research questions were asked: In children using cochlear implants, 1) Can the ECAP, EABR, and ESR be recorded at the time of cochlear implantation? 2) What is the feasibility of measuring the ECAP, EABR, and the ESR repeatedly without the use of sedation over the first year of implant use? 3) Do ECAP, EABR, and ESR thresholds or behavioral measures change over time? 4) What is the relation between ECAP, EABR, and ESR thresholds and behavioral measures of threshold and comfortably loud levels? In 68 children, ECAP, EABR, and ESR responses as well as behavioral measures of stimulation threshold and maximum stimulation were recorded at regular intervals over the first year of implant use. In each child, responses were recorded to electrical pulses provided by three different electrodes along the implanted array. Visual inspections of the stapedius reflex (V-ESR) evoked by activation of the same three electrodes at the time of surgery were performed in an additional 20 children. ECAP and EABR measures were obtained in more than 84% of electrodes tested and 89% of children tested both in the operating room at the time of implant surgery (OR) and after surgery in nonsedated children. ESRs were recorded by using immittance measures in more than 65% of electrodes tested and 67% of children tested by 3 mo of implant use, but this technique was less successful in the OR and during early stages of device use. V-ESRs and ECAP thresholds were higher in the OR than ESRs and ECAPs at postoperative recording times. EABR and ECAP thresholds did not significantly change over the first 6 and 12 mo of implant use, respectively, whereas ESR thresholds increased. Behavioral measures of threshold decreased over time, whereas maximum stimulation levels rose over time. Behavioral measures of threshold and loudness were highly correlated at all test times. ECAP, EABR, and behavioral measures were lower when evoked by an electrode at the apical end of the implanted array than by more basal electrodes. Behavioral thresholds could be predicted mainly by ECAP thresholds, whereas maximum stimulation levels could best be predicted by ESR thresholds; both were significantly affected by the age at implantation. A combination of nonbehavioral measures can aid in the determination of useful cochlear implant stimulation levels, particularly in young children and infants with limited auditory experience. These measures can be made in the operating room and can be repeated after surgery when needed. Correction factors to predict threshold stimulation levels should be based on ECAP thresholds or EABR thresholds if necessary. Correction factors should be made for at least one apical and mid-array electrode, should take into account the age of the child, and may have to be revised during the first year of implant use. Maximum stimulation levels may be best determined by using the ESR.

Fine structure of hearing threshold and loudness perception.

Hearing thresholds measured with high-frequency resolution show a quasiperiodic change in level called threshold fine structure (or microstructure). The effect of this fine structure on loudness perception over a range of stimulus levels was investigated in 12 subjects. Three different approaches were used. Individual hearing thresholds and equal loudness contours were measured in eight subjects using loudness-matching paradigms. In addition, the loudness growth of sinusoids was observed at frequencies associated with individual minima or maxima in the hearing threshold from five subjects using a loudness-matching paradigm. At low levels, loudness growth depended on the position of the test- or reference-tone frequency within the threshold fine structure. The slope of loudness growth differs by 0.2 dB/dB when an identical test tone is compared with two different reference tones, i.e., a difference in loudness growth of 2 dB per 10-dB change in stimulus. Finally, loudness growth was measured for the same five subjects using categorical loudness scaling as a direct-scaling technique with no reference tone instead of the loudness-matching procedures. Overall, an influence of hearing-threshold fine structure on loudness perception of sinusoids was observable for stimulus levels up to 40 dB SPL--independent of the procedure used. Possible implications of fine structure for loudness measurements and other psychoacoustic experiments, such as different compression within threshold minima and maxima, are discussed.

The difference between a question and a statement: A cross-dialect survey

Seven British English dialects were studied to see what prosodic distinctions are made between statements and questions in read speech. A set of Bayesian classifiers was built upon feature vectors obtained from a spectral analysis of measures of (1) f0, (2) loudness, (3) spectral slope and (4) voicing periodicity. It was found that the prosodic information useful for the question/statement distinction is distributed broadly across the utterance, and that loudness and spectral slope can be nearly as informative as f0 (voicing is less informative). The three important acoustic features carry somewhat less than one bit of information each, so prosodic information could be valuable to the listener, and the listener may be able to make the question/statement decision early in the utterance. The contrast differs from one acoustic property to the next: f0 is marked primarily by slow variations. Conversely, the spectral slope and loudness measurements primarily use shorter-wavelength features, corresponding to structures that are a syllable or two long. We also find substantial differences in the prosodic information that different dialects use, and substantial differences between speakers of the same dialect. [Research supported by the UK Economic and Social Research Council, Grant RES 00-23-1049.]

Tinnitus loudness matchings in relation to annoyance and grading of severity

Objective: To measure and compare different parameters of tinnitus loudness obtained via matching and to investigate their associations with self-reported severity of tinnitus. Methods: From the audiology department 18 patients with unilateral tinnitus of sensorineural origin were selected. They underwent pure-tone audiometry, and in a matching paradigm their tinnitus pitch was estimated. Loudness was assessed at tinnitus frequency and at the frequency of best hearing and both were expressed in sensation level (SL) and hearing level (HL). Moreover, minimal masking level (MML) with white noise was assessed as well as thresholds for the tinnitus tone and a comparison tone in the contralateral ear when tinnitus was masked. Results: Annoyance and grading of severity were associated with measures of loudness expressed in HL, MML, and pure-tone audiometry. Loudness in SL was not associated with self-reported severity. Tinnitus loudness, matched at the frequency of best hearing instead of the tinnitus frequency, appears to be less dependent on HL, while still being associated with distress and grading of severity. Conclusion: Severity of tinnitus is related to hearing thresholds, and loudness in SL provides little clinically useful information.

Jozef Zwislocki’s integrated approach to psychoacoustics

Early in the psychophysics phase of his illustrious and varied scientific career, Joe Zwislocki recognized that loudness is of key importance for understanding signal processing by the auditory system. To better comprehend just how loudness can be incorporated into basic auditory theory, Joe sought to determine the loudness‐intensity relation down to near threshold levels. Together with Hellman, this aim motivated the development of absolute magnitude‐scaling procedures. Later, Joe demonstrated that absolute scaling yields results compatible with nonmetric measures of loudness additivity. His search for a comprehensive theory of auditory function led him to deduce that both the observed proportionality between loudness and sound intensity near threshold and the compressive nonlinearity in the loudness function at moderate‐to‐high levels are generated by the peripheral auditory system. These innovative concepts were incorporated into his theoretical analyses of temporal summation and central masking. They also provided the basis of a loudness model formulated to describe loudness growth in quiet and in noise. Not only are Joe Zwislocki’s extraordinary insights compatible with recent loudness measures, his loudness model can be extended successfully to predict the growth of loudness characteristic of cochlear‐impaired hearing. [Work supported by NEDO, Japan.]

ChandraSnapshot Observations of Low‐Luminosity Active Galactic Nuclei with a Compact Radio Source

The results of Chandra snapshot observations of 11 LINERs (Low-Ionization Nuclear Emission-line Regions), three low-luminosity Seyfert galaxies, and one HII-LINER transition object are presented. Our sample consists of all the objects with a flat or inverted spectrum compact radio core in the VLA survey of 48 low-luminosity AGNs (LLAGNs) by Nagar et al. (2000). An X-ray nucleus is detected in all galaxies except one and their X-ray luminosities are in the range 5x10^38 to 8x10^41 erg/s. The X-ray spectra are generally steeper than expected from thermal bremsstrahlung emission from an advection-dominated accretion flow (ADAF). The X-ray to Halpha luminosity ratios for 11 out of 14 objects are in good agreement with the value characteristic of LLAGNs and more luminous AGNs, and indicate that their optical emission lines are predominantly powered by a LLAGN. For three objects, this ratio is less than expected. Comparing with properties in other wavelengths, we find that these three galaxies are most likely to be heavily obscured AGN. We use the ratio RX = \nu L\nu (5 GHz)/LX, where LX is the luminosity in the 2-10 keV band, as a measure of radio loudness. In contrast to the usual definition of radio loudness (RO = L\nu(5 GHz)/L\nu(B)), RX can be used for heavily obscured (NH >~ 10^23 cm^-2, AV>50 mag) nuclei. Further, with the high spatial resolution of Chandra, the nuclear X-ray emission of LLAGNs is often easier to measure than the nuclear optical emission. We investigate the values of RX for LLAGNs, luminous Seyfert galaxies, quasars and radio galaxies and confirm the suggestion that a large fraction of LLAGNs are radio loud.

Relationship between intensity and reaction time in normal-hearing infants and adults.

Reaction time (RT) to sound is known to be related to loudness in adult listeners. The purpose of this study was to determine whether infants' RT to sound decreases systematically with intensity as it does in adults. RT was measured for 24 6- to 9-mo-old infants and 11 19- to 26-yr-old adults. All participants were normal hearing, naïve listeners. The stimuli consisted of 4000 and 1000 Hz pure tones presented to the right ear through an insert earphone. Stimulus intensities ranged in 10 dB steps from 40 to 80 dB SPL for adults and 50 to 90 dB SPL for infants. Infant responses consisted of a head turn toward a reinforcer whereas adults responded by raising their hand. An additional three adults responded with a head turn. RT was defined as the time between the onset of the tone and an observer's button press indicating that a response had occurred. RT was corrected for the observer's reaction time and averaged over three to five repetitions at each level to obtain the mean reaction time (MRT) for each subject, frequency, and level. MRT decreased with increasing intensity in both infants and adults. An examination of the MRT-intensity functions suggests that the infant functions may be steeper than those of adults, although considerable variability exists between listeners. RT holds potential as a measure of loudness in infants. Whether differences in the MRT-intensity slopes exist between infants and adults is unclear. Future investigations using methods to reduce the variability of RT measurements are needed to examine potential slope differences further.

Loudness scaling in children

Loudness measurements in children have been carried out using different psychoacoustical methods. Besides absolute magnitude estimation (AME) and cross modality matching (CMM) category and non-category loudness scalings have been performed. However, there is a lack of systematic evaluation in loudness scalings with children. A clinically feasible categorical method is presented which was evaluated in 10 normally hearing children of 7 to 8 years. Furthermore, measurements with hearing disabled children were performed in the framework of hearing aid evaluation. Normal hearing children scaled slightly louder than a group of adult subjects with normal hearing. Regarding the shape of the loudness functions measured they were very similar. Particularly, they showed a steeper course at higher levels than for low input signals. Intraindividual scatter of the loudness judgements was larger for children than for adults. However, high correlation appeared between the data across test and retest. Hence, the outcome of the scalings appears to be sufficient reliable. Clinical measurements confirmed that the method is appropriate for children from approximately 5-10 years. Loudness judgements became more consistent and more subtly differentiated with increasing age and decreasing hearing loss. Especially with view of hearing aid evaluation the method can give valuable indications because of the possibility to directly measure individual loudness over a broad range of levels and frequencies.

A measure for predicting audibility discrimination thresholds for spectral envelope distortions in vowel sounds.

Both in speech synthesis and in sound coding it is often beneficial to have a measure that predicts whether, and to what extent, two sounds are different. This paper addresses the problem of estimating the perceptual effects of small modifications to the spectral envelope of a harmonic sound. A recently proposed auditory model is investigated that transforms the physical spectrum into a pattern of specific loudness as a function of critical band rate. A distance measure based on the concept of partial loudness is presented, which treats detectability in terms of a partial loudness threshold. This approach is adapted to the problem of estimating discrimination thresholds related to modifications of the spectral envelope of synthetic vowels. Data obtained from subjective listening tests using a representative set of stimuli in a 3IFC adaptive procedure show that the model makes reasonably good predictions of the discrimination threshold. Systematic deviations from the predicted thresholds may be related to individual differences in auditory filter selectivity. The partial loudness measure is compared with previously proposed distance measures such as the Euclidean distance between excitation patterns and between specific loudness applied to the same experimental data. An objective test measure shows that the partial loudness measure and the Euclidean distance of the excitation patterns are equally appropriate as distance measures for predicting audibility thresholds. The Euclidean distance between specific loudness is worse in performance compared with the other two.

Incorporation of loudness measures in active noise control

An attempt has been made to use a modified version of a standard active noise control algorithm in order to take into account the unique response of the human auditory system. It has been shown in the past that decreasing the sound pressure level at a location does not guarantee a similar decrease in the perceived loudness at that location. Typically, active noise control is based on minimizing the "error signal" from a mechanical device such as a microphone, whose response is nominally flat across the frequency response range of the human ear. However, if the response of the ear can be approximated by digitally filtering the error signal before it reaches the adaptive controller, one can, in effect, minimize the more subjective loudness level, as opposed to the sound pressure level. The work reported here entails simulating active noise control based upon minimizing perceived loudness for a collection of input noise signals. A comparison of the loudness of the resulting error signal is made to the loudness of that resulting from standard sound pressure level minimization. It has been found that the effectiveness of this technique is largely dependent upon the nature of the input noise signal. Furthermore, this technique is judged to be worth considering for use with applications of active noise control where the uncontrolled noise more prominently constitutes low range audio frequencies (approximately 30 Hz-100 Hz) than medium range audio frequencies (approximately 300 Hz-600 Hz).

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.

Computer-automated clinical technique for tinnitus quantification.

This study addresses the need for uniformity in techniques for clinical quantification of tinnitus. Because automation can be an effective means to achieve standardization, this laboratory is developing techniques to perform computer-automated tinnitus testing. The present study was conducted to demonstrate the feasibility of obtaining reliable tinnitus measures using a fully automated system. A computer-controlled psychoacoustical system was developed to quantify tinnitus loudness and pitch using a tone-matching technique. Hearing thresholds were also obtained as part of the procedure. The system generated test stimuli and simultaneously controlled a notebook computer positioned in the sound chamber facing the patient. The notebook computer displayed instructions for responding and relayed response choices through on-screen "buttons" that the patient touched with a pen device. Twenty individuals with tinnitus were evaluated with the technique over two sessions, and responses were analyzed for test-retest reliability. Analyses revealed good reliability of thresholds, loudness matches, and pitch matches. These results demonstrate that use of a fully automated system to obtain reliable measurements of tinnitus loudness and pitch is feasible for clinical application.

Relative loudness perception of low and high frequency sounds in the open and occluded ear.

A comparison of published equal loudness contours indicates that different shapes are obtained at a comfortable level when the measurements are done in an occluded ear than when they are done in an open ear, even though all measurements are expressed as dB SPL at the eardrum. This paper presents the result from a loudness balancing test which confirms this observation. Eleven normal-hearing listeners balanced the level of a 500- and a 3000-Hz octave band babble-noise to the level of a 1500-Hz octave band babble-noise. The balancing test was completed in open and occluded ears using a loudspeaker and a hearing aid receiver, respectively. A probe tube microphone was used to measure the actual levels presented near the individual's eardrum. The results show that an average of 10 dB higher level was selected for the 500-Hz octave band when listening with the occluded ear than when listening with the open ear. A large range of factors is discussed, but no physical explanation for the discrepancy was found. The findings could have consequences for psychoacoustic experiments and for the use of loudness measurements for hearing aid prescription.