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A model for predicting loudness for people with cochlear hearing loss was applied to the problem of the initial fitting of a multi-channel compression hearing aid. The fitting was based on two constraints: (1) The specific loudness pattern evoked by speech of a moderate level (65 dB SPL) should be reasonably flat (equal loudness per critical band), and the overall loudness should be similar to that evoked in a normal listener by 65-dB speech (about 23 sones for binaural listening); (2) Speech with an overall level of 45 dB SPL should just be audible in all frequency bands from 500 Hz up to about 4 kHz, provided that this does not require compression ratios exceeding about 3. These two constraints were used to determine initial values for the gain, compression ratio and compression threshold in each channel of a multi-channel compression system. This initial fitting was based entirely on audiometric thresholds; it does not require suprathreshold loudness measures. The fitting method was evaluated using an experimental fast-acting four-channel compression system. The initial fitting was followed by an adaptive procedure to 'fine tune' the fitting, and the aids were then used in everyday life. Performance was evaluated by use of questionnaires and by measures of speech intelligibility. Although the fine tuning resulted in modest changes in the fitting parameters for some subjects, on average the frequency response shapes and compression ratios were similar before and after the fine tuning. The fittings led to satisfactory loudness impressions in everyday life and to high speech intelligibility over a wide range of levels. It was concluded that the initial fitting method gives reasonable starting values for the fine tuning.

A model for predicting loudness for people with cochlear hearing loss is applied to the problem of the initial fitting of multi-channel fast-acting compression hearing aids. The fitting is based entirely on the pure tone audiogram, and does not require measures of loudness growth. One constraint is always applied: the specific loudness pattern evoked by speech of a moderate level (65 dB SPL) should be reasonably flat (equal loudness per critical band), and the overall loudness should be similar to that evoked in a normal listener by 65-dB speech. This is achieved using the 'Cambridge' formula. For hearing aids where the compression threshold in each channel can be set to a very low value, an additional constraint is used: speech with an overall level of 45 dB SPL should be audible over its entire dynamic range in all frequency channels from 500 Hz up to about 4 kHz. For hearing aids where the compression thresholds cannot be set to very low values, a different additional constraint is used: the specific loudness pattern evoked by speech of a high level (85 dB SPL, and with the spectral characteristics of shouted speech) should be reasonably flat, and the overall loudness should be similar to that evoked in a normal listener by 85-dB speech. For both cases, compression ratios are limited to values below 3. For each of these two cases, we show how to derive compression ratios and gains, and for the first case, compression thresholds, for each channel. The derivations apply to systems with any number of channels. A computer program implementing the derivations is described. The program also calculates target insertion gains at the centre frequency of each channel for input levels of 50, 65 and 80 dB SPL, and target gains at the eardrum measured relative to the level at the reference microphone of a probe microphone system.

A model for predicting loudness for people with cochlear hearing loss is applied to the problem of prescribing the frequency-gain characteristic of a linear hearing aid. It is argued that a reasonable goal is to make all frequency bands of speech equally loud while achieving a comfortable overall loudness; this can maximize the proportion of the speech spectrum that is above the absolute threshold for a given loudness. In terms of the model this means that the specific loudness pattern evoked by speech of a moderate level (65 dB SPL) should be reasonably flat (equal loudness per critical band), and the overall loudness should be similar to that evoked in a normal listener by 65 dB speech (about 23 sones). The model is used to develop a new formula - the 'Cambridge formula' - for prescribing insertion gain from audiometric thresholds. It is shown that, for a fixed overall loudness of 23 sones, the Cambridge formula leads to a higher calculated articulation index than three other commonly used prescriptive methods: NAL(R), FIG6 and DSL.

To correct for the influence of recruitment when the loudness of tinnitus is measured by a balance test in an ear with sensorineural hearing loss, an averaged loudness function was devised, which converts the sensation level (SL) of tinnitus into an estimate of the effective loudness level. This is essentially the same as a phon scale except for the difference in reference level, and is defined as the equivalent SL of the tinnitus as if measured in an ear with a bone-conduction threshold of 0 dB HL at a frequency between 500 Hz and 4000 Hz. Using this function, the median estimated loudness of tinnitus from 301 randomly selected patients was 15 dB 'effective loudness level' with a maximum of more than 60 dB. A nomogram was made for clinical use to determine the effective loudness level easily from the SL of tinnitus and the bone-conduction HTL of the test ear. Although somewhat approximate, the effective loudness level is considered to be an unbiased loudness estimate of tinnitus under the condition that only the SL of tinnitus and the bone-conduction HTL are available, and makes it easier to appreciate the actual loudness compared with a complex loudness unit such as on the sone scale.

The transfer function of the outer ear in humans was determined by using the impulse technique. Signals were delivered from 325 or 393 positions on an imaginary sphere surrounding the experimental subject. Changes of sound pressure level in the ear canal show that certain frequency bands are amplified maximally if they impinge onto the ear from certain directions. For some frequency bands there are two directions of sound incidence that cause best amplification in the ear canal. The directionality of the human pinna appears to increase at higher frequencies. The amount of amplification by the outer ear of frequencies between 2 and 15 kHz was also determined by measuring the free-field transfer function.

If a short duration pulse is added periodically every 30 s to a continuous tone, then the loudness of the continuous tone, which would otherwise remain unchanged, appears to undergo a progressive decline over a period of 3 min. The question at issue is whether the loss of loudness is actually induced by the pulse or merely made obvious. In support of the latter proposition a model has been developed which indicates how the loudness difference between the pulsed and continuous tone will increase as a result of adaptation. However, the model also predicts that a loudness loss should, in addition, be apparent in the pulsed tone itself. This has been confirmed by balancing the loudness in one ear of a 10 dB increment to a continuous tone of 60 dB at 1 kHz with an intermittent pulsed tone of the same frequency in the other. The magnitude of the loudness loss (of the order of 5 dB) accords well with the model prediction. The functional implications are that adaptation of continuous background noise should serve to reduce its masking effect upon speech and other transitory auditory stimuli rendering them more easily detectable.

Many researchers have proposed that multi-channel compression hearing aids should process sounds so as to restore loudness perception to 'normal'. However, procedures for achieving this have generally been based on measurements or calculations using narrowband stimuli, and these procedures may not be accurate for broadband sounds such as speech. Here, a model for predicting loudness for people with cochlear hearing loss is used to calculate the frequency- and level-dependent gains that would be required to restore loudness perception to 'normal' for speech-like signals. The calculations are based entirely on the pure tone audiogram, and do not require measures of loudness growth. The model was applied to several different hypothetical hearing losses, varying in slope and severity. In each case, the model was used to calculate the insertion gains (IGs) that would be required as a function of frequency so that speech-shaped noise with a level of 65 dB SPL would evoke a specific loudness pattern matching that for a normal ear. A similar procedure was applied using speech-shaped noise with a level of 85 dB SPL (with the spectral characteristics of shouted speech). The results were used to derive functions relating the required IG to hearing loss for each audiometric frequency and each speech-shaped noise level. These functions were used in turn to derive compression ratios and gains for each channel of a multi-channel compression system. The derivations apply to systems with any number of channels. The outcome is a method than can be used for the initial fitting of multichannel compression hearing aids, so as to restore loudness perception to near 'normal' for broadband speech-like signals.

A recent study revealed that most patients were wearing National Health Service hearing aids that were capable of exceeding their uncomfortable loudness level (ULL) measured clinically (Munro et al., 1996). However, there is little evidence to show that these clinical measurements are a valid indicator of real-world auditory discomfort. The aim of this study was to investigate the relationship between ULL and real-world discomfort. The study involved 20 adult subjects, aged 41-92 years, who had been fitted monaurally with an NHS hearing aid. ULLs were measured using a probe-tube microphone situated close to the eardrum. Individual real ear to coupler differences were added to the SSPL90 in order to predict the maximum power output (MPO) of the hearing aid at the eardrum. Subjects completed a questionnaire designed to rate the loudness of different environmental sounds. The results show that the more the MPO value exceeded the ULL value, the more likely it was that the subjects reported loudness tolerance problems to environmental sounds of long duration. There was a statistically significant correlation between the ULL and discomfort ratings for sounds of longer duration, such as traffic and wind noise; but not for shorter-duration sounds, such as door banging. Subjects did not express real-world auditory discomfort when the MPO value matched the ULL value. These findings support the argument for setting hearing-aid MPO close to ULL.

A series of studies examining the interaction between the characteristics of individual tinnitus sufferers and the effectiveness of the methods used to assist them has been conducted. The first of these studies provided a baseline description of 96 people with tinnitus, according to a range of audiological and psychological variables. In the present paper four differing tinnitus management programmes are described and the related changes in tinnitus perception reported three months after tinnitus management training. For the majority of subjects, the tinnitus was less annoying and less distressing three months after attending tinnitus management training. However, the majority of subjects reported no change in tinnitus loudness, or tinnitus awareness and no change in their tinnitus coping ability. Subjects receiving low level white noise stimulation reported greater improvement in tinnitus coping ability than subjects who received information and relaxation training, although there was no associated improvement in tinnitus awareness. Subjects' beliefs about tinnitus and preferred coping style may have influenced the reported benefit or otherwise of the differing tinnitus management techniques.

It is generally agreed that the maximum output from a hearing aid should not exceed the subject's uncomfortable loudness level (ULL). However, this relationship is not easily defined as electroacoustic data are usually measured in a 2 cc coupler and auditory measurements are usually obtained from supra-aural transducers calibrated in a 6 cc coupler. The aim of the study was to investigate this relationship in 21 adults who were being fitted with a hearing aid for the first time. A probe-tube microphone system was used to measure the sound pressure level of both variables in the ear canal. The measurement of ULL was determined using the method recommended by the British Society of Audiology (1987). The ULL values were around 110 dB SPL (+/-10) when measured in the ear canal. The maximum output of the hearing aid was obtained by correcting the SSPL90 with the subject's own real ear to coupler difference. The results revealed that the real ear saturation response (RESR) of the newly fitted hearing aid was typically 115-120 dB SPL (+/-8). The RESR exceeded the ULL for 19 (90%) subjects on average at five of the seven frequencies and by 12 dB. While further research is needed to determine whether discomfort occurred in real life situations, the implications are that the subject may use the hearing aid at less than optimum settings to prevent loudness discomfort or may ultimately reject the hearing aid altogether.

Individuals with higher frequency hearing loss, when tested at 1000 Hz, showed more loudness adaptation at 40 dB HL and less at 60 dB HL (ISO) than the normal listeners. Adaptation was measured with the monaural method described by Weiler, Sandman and Pederson (1981), now called the Ipsilateral Comparison Paradigm (ICP) by Dange et al. (1993). Using the same method Korman (1986) had shown that a complex combination of stimulus conditions, including intensity, produced differences between a similar group with high frequency hearing loss and normals. The current results confirm the value of this method for studying adnormalities in the loudness function at middle intensities. Because it is a quick and reliable method we believe it has potential for clinical use but acknowledge considerable research and development is necessary.

In 20 patients diagnosed with Menière's disease, transcutaneous nerve stimulation (TNS) and applied relaxation (AR) were used as a treatment aimed at reducing tinnitus and dizziness and increasing hearing ability. The main aim of the study was to examine whether TNS could be regarded as a more beneficial treatment regimen than AR. An experimental between-group cross-over design was used. The results from the experimental phase (group comparisons) showed a significantly increased ability to hear for the TNS group when measured on visual analogue scales. During the same period, the AR-group showed a significant hearing improvement for the ear not primarily affected by Menière's disease as measured with pure tone audiometry. The vestibular tests did not reveal any significant changes either after TNS or AR intervention. Tinnitus matching showed changes of pitch and loudness before and after both TNS and AR intervention. However, no statistically significant changes between treatment regimes were found on these measures. The results from this study did not show TNS to be superior to AR in reducing tinnitus, dizziness or increasing hearing ability.

This study expanded upon previous work (Gelfand & Silman, 1985) on the relationship between functional components (the difference between the nonorganic and resolved thresholds) and the underlying organic hearing levels. The nature of nonorganic hearing loss (NOHL) was studied with respect to hearing sensitivity after resolution of the nonorganic components in 25 patients with unilateral NOHLs. Most of the subjects had an organic hearing loss underlying the functional components. The configuration of the functional components as a function of frequency was related to that of the resolved hearing levels in a manner similar to that reported for bilateral NOHLs. The strategy employed to exaggerate the loss in the ear with the nonorganic overlay appeared to be unrelated to the nature of the loss in the opposite ear, but the perception of an interaural difference might in some way bias the patient to 'choose' a unilateral NOHL as opposed to a bilateral one. The findings confirm and expand upon the prior ones, suggesting the use of an internalized loudness-based anchor by patients with NOHLs. Thus, the pure tone configuration of NOHL is consistently accounted for on the basis of known and explainable auditory factors regardless of whether the hearing levels are exaggerated in one or both ears.

Four words lists of a German Speech Intelligibility Test (DIN 45621) were recorded at 60 and 75 dB SPL. Both recordings were presented to 20 normally hearing subjects at 75 dB SPL via free-field equalized earphones. Discrimination in noise was significantly better in the original recording at 60 dB SPL. The better understanding may be explained by a more favourable consonant-vowel intensity ratio. Moreover, a significant increase in fundamental frequency could be demonstrated at the higher recording level. The implications for speech audiometry and hearing aids are discussed. Furthermore, it was found from loudness comparisons that both recordings were equally loud at a level of 75 dB SPL. However, significantly increased loudness was indicated in the 75 dB SPL recording by the loudness calculation procedure ISO 532 B.

In a nation-wide investigation, covering all the hearing centres in Sweden, a study was made of adaptation processes, subjective discomfort from tinnitus, subjective loudness of tinnitus and psychological complaints in 3372 subjects by means of a questionnaire. The most important predictors of discomfort from and adaptation to tinnitus were found to be the controllability and the degree of maskability by external sounds, i.e. the subject's coping abilities or internal-external locus of control. Increased control and masking effects from the environment imply a decrease in discomfort and better adaptation. The most important predictor of worsened subjective loudness of tinnitus was the duration of the tinnitus. That is, subjects who had had tinnitus for a longer time perceived the loudness as more intense. The psychosomatic factors which most strongly predicted increased discomfort from and decreased tolerance to tinnitus were depression and insomnia. These findings have theoretical and practical implications for the management and treatment of tinnitus.

An experiment was performed using low-level ultrasound in an attempt to inhibit tinnitus during and after stimulation. The method used a double-blind crossover technique with a placebo. Forty subjects were tested, and they generally reported little or no change in their tinnitus, the results from placebo and ultrasound not being statistically different. It cannot be concluded, therefore, that the ultrasound we were using has any beneficial effect on tinnitus. These results do not confirm the findings of the pilot study using the same ultrasound devices (Carrick et al., 1986).

The present study attempted to fit Weiler and Hood's (1977) quantitative model for loudness coding to an additional set of simultaneous dichotic loudness balance (SDLB) adaptation data. The error of prediction for test values 10 dB above adapting intensity for 12 normal-hearing listeners was –2.7 to –4.7 dB, an average of –3.5 dB. Since the error of prediction was so nearly constant (S.D.=≤.737 dB), it seemed reasonable to attribute it to differences in procedural technique, and to conclude that the loudness model does account for a large component of coding in the adaptation results.The hearing of 24 normal hearing children ranging in age from 18 to 32 months was tested by TROCA and peep-show, two operant conditioning techniques differing only in the type of reward. Children between 18 and 24 months consistently exhibited poorer thresholds (lowest response levels) than children between 25 and 32 months. The older children required fewer trials for threshold determination and took less time in completing ...

This report describes a three-centre study of the effectiveness of tinnitus maskers, combination instruments (masker plus hearing aid), and hearing aids in the management of tinnitus. Some 472 patients entered the study with 382 reaching the first evaluation session after a minimum period of 6 months from fitting, and 206 reaching the second evaluation not less than 6 months after the first. The study included two control groups, by which to assess the comparative benefit to be derived solely from the investigation and counselling of such patients. The principal results were as follows: thorough investigation and careful counselling do much to help the patient; much further benefit is given by tinnitus masking instruments of various kinds; maskers are more often effective than hearing aids, although the latter are frequently the most appropriate first treatment of those patients who have substantial (but not yet treated or insufficiently treated) hearing difficulties as well; there is no evidence of masking having any harmful effect on hearing. None of the audiometric or tinnitus tests currently employed can be regarded as predictive, either of tinnitus severity, or of the eventual outcome of masking therapy, however certain measurements may help as a guide to patient management.

Previous reports indicate that adaptation measured by the technique of successive magnitude estimations is not found above 30 dB SL (Fishken et al., 1977; and others). Although the present study confirmed this finding at 60 dB SPL for the original procedure, it was found that a modification of the magnitude estimation procedure resulted in significant loudness adaptation at this intensity. Introduction of a 20-dB increment for 5 s, every 30 s, resulted in a marked and statistically significant decline in successive loudness judgements of the 60-dB tone. In addition, the decline in reported loudness magnitude was cumulative and progressive throughout the 7-min duration of the monaural stimulus. This is typical of classical results found with simultaneous dichotic loudness balances.

With binaural stimulation the two specific parameters that can modify the neural responses substantially are the intensity differences and the time of arrival of the stimulus at the two ears; these events on electrophysiological evidence, being mediated at the superior olivary complex and at the inferior colliculus, the origins of Waves III and V respectively. Comparison of the brainstem auditory-evoked potentials to monaural stimulation with that due to binaural stimulation reveals a significant increase only in the amplitude of Wave V. The amount of increase is reduced from 68.7% with equal intensities at the two ears to 44% with a 10-dB interaural intensity difference. With a 20-dB interaural intensity difference the amplitude of Wave V reverts to that due to monaural stimulation. The 68.7% greater amplitude for Wave V was not due to effective increase in loudness sensation on binaural stimulation (which is equivalent to a monaural increase in intensity of 3 dB) but to binaural summation. In contrast to Wave V, Wave III decreased in amplitude below that resulting from monaural stimulation with intensity differences of 10 and 20 dB at the two ears. This supports the suggestion of inhibitory processes at that level of the brainstem. As only Wave V shows binaural summation the region of inferior colliculus is suggested as the site for the occurrence of this phenomenon. Binaural interaction can also be demonstrated within a limited range with intensity differences at the two ears.

Above a critical level (CL) of fatiguing tone, temporary threshold shift (TTS) rises rapidly with intensity. Using a fatiguing tone of 1000 Hz, threshold shift following 1 min stimulation at varying intensities was measured at the same frequency in 55 normal subjects and the CL determined for each. In a second and more limited study, TTS was measured at a frequency half an octave above that of the fatiguing tone. A significant inverse correlation was established between hearing level (HL) and CL at the same frequency with a fall of 2.5 dB in the latter for every 10 dB rise in the former. CLs measured half an octave above the fatiguing tone frequency were appreciably lower by 5 to 11 dB. No correlation was apparent between TTS and HTL, implying that TTS and CL are subserved by differing physiological mechanisms. The findings have relevance to the topic of susceptibility to noise-induced hearing loss and the formulation of damage risk criteria.

Studies of the listening habits of personal cassette player users have been carried out in both Southampton and Turin. The results have been compared with other researches carried out independently in London and Nottingham. Patterns of noise exposure have been examined and estimates of hearing damage risk hypothesised. Habitual users of such devices could suffer adverse effects and should be aware of the symptoms associated with temporary threshold shifts in hearing.

(1985). Practical aspects of the instrumental management of tinnitus. British Journal of Audiology: Vol. 19, No. 2, pp. 147-150.

In order to determine the relationship between binaural phase localization and auditory adaptation, subjects were asked to perform a series of phase-based localization tasks, as well as an SDLB adaptation task. A binaurally presented 400 Hz tone was used for midplane localization tasks, and adaptation balances. The tone was presented monaurally during adaptation after binaural localization and the SDLB pre-test. Following 7 min exposure, subjects readjusted phase to centre the binaural stimulus in the midline, and then adjusted intensity to determine dB of adaptation. No consistent or statistically significant change in phase settings occurred. There was a significant decline in the balance intensity as a function of adaptation. A further re-establishment of the midline by phase manipulation also showed no localization effect. For the stimulus values used in the present study, there was no inter-effect of binaural phase localization, and SDLB auditory adaptation.

The loudness of a continuous pure tone does not appear to change with time unless an interrupted tone is introduced at intervals during the course of the test; in consequence it is held that it is the interrupted tone which induces the loudness loss. This, however, cannot be called on to account for the marked change in quality or 'timbre' of a sustained pure tone which occurs over a period of time and which has the attributes of 'tonal adaptation', matching the time course of loudness adaptation revealed by dichotic loudness balance and other procedures. It is argued that the latter have to do with the measurement of sensation while judgement of the loudness of a continuous tone in isolation involves higher-order perceptual processes.

This study was designed to determine the intelligibility of speech at two intensity levels using two different conditions (broad band and high pass filtered speech) and to determine the vowels and consonants most affected by the conditions imposed. The ten subjects were all stimulated with 50 words of the CID W-22 series at two levels of intensity (30 db SL and 15 dB SL) each in the filtered and broad-band (unfiltered) conditions. The results tended to indicate that the type of condition (filtered or unfiltered) did not affect the speech comprehension until the intensity of the filtered signal approached 15 dB SL. It was also determined that consonants and vowels identification were only slightly affected by filtering if the intensity of the signal is above 15 dB SL.

Multivariate statistical techniques were used to re-analyse the data from the recent DHSS multi-centre masker study. These analyses were undertaken to three ends. First, to clarify and attempt to replicate the previously found factor structure of complaints about tinnitus. Secondly, to attempt to identify common factors in the change or improvement measures pre- and post-masker treatment. Thirdly, to identify predictors of any such outcome factors. Two complaint factors were identified; 'Distress' and 'intrusiveness'. A series of analyses were conducted on change measures using different numbers of subjects and variables. When only semantic differential scales were used, the change factors were very similar to the complaint factors noted above. When variables measuring other aspects of improvement were included, several other factors were identified. These included; 'tinnitus helped', 'masking effects', 'residual inhibition' and 'matched loudness'. Twenty-five conceptually distinct predictors of outcome were identified. These predictor variables were quite different for different outcome factors. For example, high-frequency hearing loss was a predictor of tinnitus being helped by the masker, and a low frequency match and a low masking threshold predicted therapeutic success on residual inhibition. Decrease in matched loudness was predicted by louder tinnitus initially.

In two recent articles, Hood and Wade (1982) and Weiler et al. (1981) have argued that the loudness of a steady tone does not appear to decline over time unless listeners are given a reference sound by which to judge loudness. The present experiments show, by the method of successive magnitude estimation, that listeners do not need a reference sound in order (1) to track accurately the decline in the loudness of a tone slowly decreasing from 60 to 40 dB SPL or (2) to track the loudness decline of a constant-intensity tone under special conditions that lead to adaptation. Since a reference sound is not needed by listeners to track a decline in loudness, and since Hood and Wade and Weiler et al. have found a decline with a reference but not without, it follows that adding a reference sound to a sustained sound must induce adaptation that otherwise does not occur. In support of that interpretation, the present measurements show that when subjects are told to ignore the same reference sound as used by Hood and Wade and by Weiler et al.--an increment every 30 s to a steady tone--loudness still declines. The bigger the increment (20 dB v. 5 dB) and the longer (5 s v. 1 s), the more loudness declines. Thus, loudness adaptation may be induced not only by a contralateral intermittent sound (Botte et al., 1982) but also by an ipsilateral intermittent sound. However, under normal listening conditions at levels above about 30 dB SL, loudness does not adapt.

Recently it has been demonstrated that auditory adaptation can be measured with a monaural technique (Weiler and Friedman, 1973; Weiler and Gross, 1976; Feaster and Weiler, 1975). Because the magnitude of adaptation measured monaurally was nearly identical to that measured binaurally in other experiments, it was assumed that they measured the same phenomenon or phenomena. In the present study the same group of subjects were tested for magnitude of adaptation both monaurally and binaurally. The means were 11.75 dB and 12.17 dB, respectively (N=13). Despite nearly identical means for the present conditions there was no significant correlation (r=+.27) between the magnitude of adaptation measured under the two conditions. Except for the possibility that individual differences in the ability to do monaural versus binaural tasks may have obscured individual similarities in adaptation, the only other explanation the authors can suggest is that the two techniques measure different aspects of loudness adaptation.

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.

Critical band estimation was performed in thirty-three patients with sensorineural hearing loss by the method of loudness summation, using noise bands centred around 1 kHZ. In 17 patients the hearing loss was of hereditary origin, in 16 patients of various, mostly unknown, origin. The normal loudness difference between broad band noise and narrow band noise decreased with increasing hearing loss, most pronounced in recruiting ears. Judged individually, 1/3 of the patients appeared to have a widened critical band, but several biases appeared to be responsible for these results. The pooled data indicated a normal critical band, both in patients with hearing losses less than 50 dB HL and in patients with hearing losses greater than or equal to 50 dB HL. Based on this finding, the validity of the critical band as a measure of the frequency selectivity of the ear is discussed and a theory is proposed for the anatomical and functional correlate of the critical band in loudness summation.

Short latency (10 ms post-stimulus-time) auditory evoked potentials are a useful tool for assessing the hearing integrity at different frequency bands, especially if frequency-specific stimuli, like tone bursts, are used. However, a proper interpretation of the evoked potentials should rely upon the understanding of the single auditory nerve units activity patterns and their relations with the gross potentials, under the same stimulating conditions. In this paper, the basic properties of the burst evoked PST histograms of single units are explained with the aid of a model for the cochlear events. The relationships between single units activity and the gross potentials are then analysed on this ground, in particular for what concerns the Action Potential input-output latency curve, the off-response rising at the burst offset and the growth of N2.

Techniques have been devised whereby the levels at which users of personal cassette players listen to tape-recorded sounds through lightweight headphones may be measured and expressed in terms of free-field equivalent continuous A-weighted sound pressure levels. Data have been obtained on over 60 users of such devices who variously listened, in laboratory and field conditions, to music and speech against quiet and noisy backgrounds. The results have been interpreted in terms of noise exposure. Comparison with damage risk criteria indicates that 5% of the sample are listening in such a manner that habitual use would constitute a damage risk to hearing.

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.

A monaural simultaneous balance technique was used to compare amounts of adaptation for two conditions: (1) with the test intensity equal to the adapting intensity, and (2) with the test intensity +10 dB above the adapting intensity. Previous, findings (Weiler and Hood, 1977) showed a decline in measured adaptation for the second condition using simultaneous binaural balances. That this was not the case for the monaural balances investigated in this study may indicate different adaptation-induced auditory changes are being measured monaurally vs. binaurally.