Loudness Scaling Research Articles

Range and regression, loudness scales, and loudness processing: Toward a context-bound psychophysics.

How does context affect basic processes of sensory integration and the implicit psychophysical scales that underlie those processes? Five experiments examined how stimulus range and response regression determine characteristics of (a) psychophysical scales for loudness and (b) 3 kinds of intensity summation: binaural loudness summation, summation of loudness between tones widely spaced in frequency, and temporal loudness summation. Context affected the overt loudness scales in that smaller power-function exponents characterized larger versus smaller range of stimulation and characterized magnitude estimation versus magnitude production. More important, however, context simultaneously affected the degree of loudness integration as measured in terms of matching stimulus levels. Thus, stimulus range and scaling procedure influence not only overt response scales, but measures of underlying intensity processing.

Speech Enhancement by Filtering in the Loudness Domain.

Several attempts that employed dynamic compression to compensate for cochlear impairment in combination with recruitment have failed to improve speech intelligibility. One reason is the attenuation of dynamic intensity modulations in the range of 1 to 50 Hz which contribute significantly to speech discrimination. In the approach presented here, these modulations were enhanced rather than attenuated by an envelope highpass filter operating in the loudness domain as follows: the output of a filterbank was lowpass filtered to extract the envelope, converted to loudness in accordance with normal hearing, highpass-filtered and converted back to the 'desired' envelope by the loudness characteristic of each individual hearing-impaired subject. The output signal was finally obtained by summing the outputs of the filterbank channels after correcting their amplitudes. The algorithm was implemented by a computer to simulate a digital hearing aid fitted to the loudness-scaling function of each individual. Loudness scaling and speech-discrimination data in quiet and in noisy conditions are presented for 2 impaired subjects with and without highpass filtering in the loudness domain. The results indicate that loudness compensation without highpass filtering improves speech intelligibility for a wide range of input levels by achieving an optimum gain characteristic at all input levels. The highpass filter applied to the envelope has no noticeable effect on speech discrimination either in quiet or in noise.

Dichotic, diotic, and monaural summation of loudness: a comprehensive analysis of composition and psychophysical functions.

In a series of six experiments, the method of magnitude estimation, constrained by a multivariate model, was used to assess the rules that govern the summation of the loudness of two-tone complexes. This methodology enabled us to specify the amounts of summation and simultaneously to construct the corresponding loudness scales. The components had different frequency separations and in the different experiments were presented (1) dichotically, a different frequency to each ear; (2) diotically, to both ears; and (3) monaurally. Results replicated and in some conditions extended known features of multiple signal processing by the auditory system. Thus, qualitatively different rules of loudness integration appeared. For monaural and diotic modes of stimulation, overall loudness depended on total sound energy within the critical band, but on the simple sum of component loudnesses beyond the critical band. For dichotic presentations, a fully additive rule of loudness summation appeared, regardless of frequency spacing. For the latter (but not the former), loudness summation was perfect, with the underlying loudness scales closely approximating Stevens's sone scale.

Application of an auditory model to speech recognition

Some aspects of auditory processing are incorporated in a front end for the IBM speech-recognition system [F. Jelinek, "Continuous speech recognition by statistical methods," Proc. IEEE 64 (4), 532-556 (1976)]. This new process includes adaptation, loudness scaling, and mel warping. Tests show that the design is an improvement over previous algorithms.

Loudness Scales from Loudness Processes: A Multivariate Approach

Five subjects were required to judge the loudness of pure tones that varied in intensity and duration (Experiment 1), in intensity and frequency (Experiment 2), or in duration and frequency (Experiment 3). Results of all three experiments were consistent with the respective models of sensory integration expected to underlie the various judgmental tasks (multiplicative for the first experiment, unidimensional for the latter two). Despite the use of common stimulus values across experiments and instructions to judge solely loudness, different loudness scales emerged. This outcome supports a task dependent, multirepresentative scheme for loudness.

Speech enhancement for the hearing impaired by envelope filtering on a loudness scale

Dynamic compression systems for sensorineural hearing‐impaired subjects reduce intensity fluctuations, although they are an important cue for understanding speech. To overcome this effect, an envelope high‐pass filter operating in the loudness domain is evaluated, which even enhances these intensity modulations: The output of a filterbank is low‐pass filtered to extract the envelope of incoming speech. Loudness scaling data from normal listeners and from each individual impaired listener is used to convert the envelope to a loudness scale value and to convert the high‐pass‐filtered loudness back to the “desired” envelope value, respectively. The output signal is finally obtained by summing up the filterbank channels after correcting their amplitude. Loudness scaling and intensity modulation discrimination data of several sensorineural hearing‐impaired subjects will be presented, as well as speech intelligibility scores for a German CVC rhyme test with and without the algorithm. First results indicate that even no loudness filtering improves speech intelligibility in a wide range of input levels. However, the effect of high‐pass filtering in the loudness domain is only moderate. [Work supported by Deutsche Forschungsgemeinschaft.]

The additivity of loudness across critical bands: a conjoint measurement approach.

Five subjects were required in each trial to compare directly two sounds and to indicate which sound was louder. Each of the 64 sounds employed consisted of a combination of one of eight intensity levels of a 2-kHz tone and one of eight intensities of a 5-kHz tone. If, as Fletcher and Munson (1933) argued, loudness is additive for tone combinations in which the frequencies are widely separated, then subjects’ judgments should reflect the summed loudnesses of the 2- and 5-kHz tones in a two-tone combination. Judgments of individual subjects were shown to satisfy the conditions for an additive structure, and individual loudness scales were constructed. These loudness scales varied from subject to subject. Since this paired comparison procedure minimized response biases, the results suggest substantial individual differences in the sensory representation of sound intensity. The relations among sensory scales derived from other structured sensory judgments, such as binaural loudness, are discussed.

Scaling loudness over short ranges: a reply to Poulton.

Poulton (1984) has recently reopened an old debate about the form of the function relating loudness to the sound-pressure level of the signal. Despite the large body of evidence developed on this subject by S. S. Stevens and his associates showing that a power function provides a good description of loudness judgment both for tones and, to a less exact degree, for noise, Poulton now raises again the Fechnerian idea that loudness is proportion~l to the logarithm of sound intensity or, in the terms of hIS title, that loudness judgments are linear with decibels. In our view, however, the evidence offered to support this claim is unconvincing. Two sets of data are presented. One set, published for the first time, concerns numerical judgments of loudness for a set of six intensities of white noise ranging from 80 to 85 dB(A) in steps of 1 dB. After two repetitions, intended to familiarize the subjects with the stimulus set, each stimulus was presented following the 80-dB stimulus, designated as the standard and assigned the value of 10 on the scale of loudness. The set was presented to all subjects in the same fixed irregular order three times in succession. Before considering the results Poulton obtained, it is useful to consider what outcomes are to be expected given both the power law and the logarithmic rule proposed by Poulton. First, assume a power function with an exponent of 0.7 (a value consistent with both Poulton's data and those reported by R. Teghtsoonian and M. Teghtsoonian [1978] for the same range of intensities, but using 3-kHz tones). If the standard is called 10, the succeeding five should be called 10.84, 11.75, 12.74, 13.80, and 14.96, and since, as Baird and Noma (1975), as well as Poulton and others, have noted, unpracticed subjects are inclined to restrict themselves to integral values in the region of numbers near 10, the expected judgments for the full set of six are simply 10, 11, 12, 13, 14, and 15. By comparison, Poulton's proposal that the average subject adds one unit of loudness for every decibel ~e~ns that beginning with a standard called 10, the remammg values will be called 11, 12, 13, 14, and 15. It belabors the obvious to note that the two predictions are identical. The numerical example simply makes concrete a well-

Dual loudness scales in individual subjects.

Each of 7 subjects matched the loudness of a single tone to the loudness differences within tone pairs (Experiment 1), gave magnitude estimations of those differences (Experiment 2), and gave magnitude estimations of single tonal loudness (Experiment 3). Individual subjects used several loudness scales to perform these tasks, in accordance with Marks's (1979b) theory. At least 3 subjects used the same scale to match loudnesses to loudness differences and to give magnitude estimations of the loudness of single tones (Experiments 1 and 3), but used a shallower sloped scale when giving magnitude estimations of loudness differences (Experiment 2).

Dual loudness scales in individual subjects.

Dual loudness scales in individual subjects.

Individual differences in loudness processing and loudness scales.

Parameters of the psychophysical function for loudness (a 1000-Hz tone) were assessed for individual subjects in three experiments: (a) binaural loudness summation, (b) temporal loudness summation, and (c) judgments of loudness intervals. The loudness scales that underlay the additive binaural summation closely approximated S. S. Stevens's (1956) sone scale but were nonlinearly related to the scales that underlay the subtractive interval judgments, the latter approximating Garner's (1954) lambda scale. Interindividual differences in temporal summation were unrelated to differences in scaling performance or in binaural summation. Although the exponents of magnitude-estimation functions and the exponents underlying interval judgments varied considerably from subject to subject, exponents computed on the basis of underlying binaural summation varied less. The results suggest that interindividual variation in the exponent of magnitude-estimation functions largely reflects differences in the ways that subjects use numbers to describe loudnesses and that the sensory representations of loudness are fairly uniform, though probably not wholly uniform, among people with normal hearing. The magnitude of individual variation in at least one measure of auditory intensity processing, namely, temporal summation, seems at least as great as the magnitude of the variation in the underlying loudness scale.

Individual differences in loudness processing and loudness scales.

Parameters of the psychophysical function for loudness (a 1000-Hz tone) were assessed for individual subjects in three experiments: (a) binaural loudness summation, (b) temporal loudness summation, and (c) judgments of loudness intervals. The loudness scales that underlay the additive binaural summation closely approximated S. S. Stevens's (1956) sone scale but were nonlinearly related to the scales that underlay the subtractive interval judgments, the latter approximating Garner's (1954) lambda scale. Interindividual differences in temporal summation were unrelated to differences in scaling performance or in binaural summation. Although the exponents of magnitude-estimation functions and the exponents underlying interval judgments varied considerably from subject to subject, exponents computed on the basis of underlying binaural summation varied less. The results suggest that interindividual variation in the exponent of magnitude-estimation functions largely reflects differences in the ways that subjects use numbers to describe loudnesses and that the sensory representations of loudness are fairly uniform, though probably not wholly uniform, among people with normal hearing. The magnitude of individual variation in at least one measure of auditory intensity processing, namely, temporal summation, seems at least as great as the magnitude of the variation in the underlying loudness scale.

Loudness scaling and masking in rats.

Loudness scaling and masking in rats.

Loudness scaling and masking in rats.

Two groups of rats were trained on operant discriminations in which the discriminanda were two different sound pressure levels of a 4-kHz tone. The discriminanda were chosen so that the loudness difference between stimuli was equivalent for each group when calculated from a power function with an exponent of .35. Half of each group learned the discrimination in quiet, and the other half learned it in a background of white noise. Within the quiet and the noise conditions, the asymptotic discriminability of stimuli separated by equal loudness differences was equivalent, and discriminability was lower in noise. This is consistent with both the human literature on masked loudness and a model of psychophysical scaling (Pierrel-Sorrentino & Raslear, 1980) in which animals judge perceived differences between stimuli.

Parametric studies of tinnitus masking and residual inhibition.

A study was made of the relation between tinnitus masker composition (frequency, bandwidth, intensity duration) and the time course and magnitude of residual inhibition (RI). RI was determined by methods of (a) loudness estimation - where the subject varied the pointer position on a loudness scale (b) loudness balance - where the tinnitus loudness was maintained in loudness balance in the period following masking with a tone of variable intensity presented to the opposite ear. In addition, sensitivity change (temporary threshold shift, TTS) in the tinnitus and masker frequency regions was measured by determining tone thresholds (using a tracking technique) before and after masker presentation. The key findings were as follows: (I) RI depends on masker centre frequency. The frequency producing maximal RI is usually lower than the tinnitus frequency (as determined by pitch matching). (2) In some subjects only narrow-band noise produces RI. (3) RI is proportional to the masker intensity provided the tinnitus is completely masked; little or no RI is produced by a partial masker. (4) For the masker durations used (in the range 10 s to 10 min) RI duration is linearly related to the logarithm of masker duration. (5) A second masker presentation during RI does not potentiate RI. (6) Contralateral masking did not produce RI. (7) maskers producing RI also produce TTS around the tinnitus frequency. (8) The TTS magnitude and the time course of TTS appear to be related to RI.

Bright sneezes and dark coughs, loud sunlight and soft moonlight.

Synesthetic metaphors (such as "the dawn comes up like thunder") are expressions in which words or phrases describing experiences proper to one sense modality transfer their meanings to another modality. In a series of four experiments, subjects used scales of loudness, pitch, and brightness to evaluate the meanings of a variety of synesthetic (auditory-visual) metaphors. Loudness and pitch expressed themselves metaphorically as greater brightness; in turn, brightness expressed itself as greater loudness and as higher pitch. Although loudness thus shared with brightness a metaphorical connection, pitch and brightness showed a connection that was closer and that applied more generally to different kinds of visual brightness. The ways that people evaluate synesthetic metaphors emulate the characteristics of synesthetic perception, thereby suggesting that synesthesia in perception and synesthesia in language both may emenate from the same source-from a phenomenological similarity in the makeup of sensory experiences of different modalities.

Loudness adaptation: real or illusory.

There is general agreement that, except at low sensation levels, the loudness of a continuous pure tone does not appear to change with time. By contrast, using a simultaneous dichotic loudness balancing procedure (SDLB) a substantial fall in loudness can be revealed. As a result it has been held that the latter does not represent a loudness loss in real terms but is a manifestation of some form of central binaural interaction possibly involving localization mechanisms. In two studies reported here, one involving a loudness scaling procedure using as a standard a reference tone of 65 dB (HL) and the other a loudness doubling procedure, a loudness loss has been clearly demonstrated following sustained stimulation with a continuous 60-dB (HL), 1000-Hz tone applied monaurally. The progression of the loudness loss with time follows a similar course to that found with the SDLB procedure. In consequence it is concluded that both represent a loudness loss in real terms and that inability to detect a change in loudness over time of a continuous tone results from the absence of any reference standard by which it can be judged.

Survey of cochlear implant work

The cochlear implant has recently seemed useful enough to be considered by some as a clinical procedure. This paper presents a review of the progress made on cochlear implants worldwide. Data are presented which contrast the results obtained in different labs on similar tests: threshold detection, pitch and loudness scaling, chronaxie, and difference limen tests. Models to account for some of these results are given. Four centers (San Francisco, Vienna, Salt Lake City, and Melbourne) have reported surprisingly good speech comprehension scores. We discuss the psychoacoustic characteristics which may relate to these scores and demonstrate that many implant patients show results which are expected quite typically in cochlear dysfunction. Thus the limits on speech processing in the hard-of-hearing may apply as well to implant patients, regardless of the method of speech coding. We also stress the lack of evidence confirming the assumed greater usefulness of multi-channel implants over single channel devices. Finally, a careful look is given to the risks involved in these procedures, specifically those of bone and tumor growth, device replacement, and the psychological effects from device failure.

Loudness and reaction time: I.

It is widely assumed, based on Chocholle’s (1940) research, that stimuli that appear equal in loudness will generate the same reaction times. In Experiment 1, we first obtained equal-loudness functions for five stimulus frequencies at four different intensity levels. It was found that equal loudness produced equal RT at 80 phons and 60 phons, but not at 40 phons and 20 phons. It is likely that Chocholle obtained equivalence between loudness and RT at all intensity levels because of relay-click transients in his RT signals. One main conclusion drawn from Experiment 1 is that signal detection (in reaction time) and stimulus discrimination (in loudness estimation) require different perceptual processes. In the second phase of this investigation, the RT-intensity functions from six different experiments were used to generate scales of auditory intensity. Our analyses indicate that when the nonsensory or “residual” component is removed from auditory RT measures, the remaining sensory-detection component is inversely related to sound pressure according to a power function whose exponent is about — 3. The absolute value of this exponent is the same as the .3 exponent for loudness when interval-scaling procedures are used, and is one-half the size of the .6 exponent which is commonly assumed for loudness scaling.

Experimental Investigation in the Anechoic Chamber on the Loudness of Acoustic Noise Caused by A.C. Corona

The paper reports on an experimental investigation in the anechoic chamber on the physiological effects of the acoustic noise caused by a.c. corona. The first part of the investigation includes a comparison of loudness of a few corona noises having different frequency spectra anid, in particular, different levels of the 100 Hz component. On the basis of the results obtained, conclusions are drawn on the most suitable weighting methods for the corona noise and possible corrections to the usual A-weighting method are suggested. The second part of the investigation considers the problem of the scale of loudness for the corona noise (variation of the loudness with the sound pressure level of the noise) and includes also a comparison of loudness of the corona noise with other types of noises. The results obtained may be useful in defining rational criteria for the choice of the acceptable levels of corona noise.