Tinnitus Facts, Theories, and Treatments (1982) / Chapter Skim
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3 Measurement Procedures
3 Measurement Procedures
Pages 32-54
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From page 32... ...
the psychophysical procedures, which are already unusual and troublesome for many naive subjects, can be made additionally difficult and frustrating by short-term fluctuations in the tinnitus; and (2) these short-term and long-term fluctuations necessarily create an uncertainty as to whether what is measured on a given day is truly representative of the tinnitus experienced by the sufferer.
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From page 33... ...
What a "high-pitched squeal" is to a piccolo player and to a nonmusician who has considerable highfrequency hearing loss obviously could be very different. Further, the words chosen by a tinnitus sufferer as best describing his or her experience may or may not touch upon all of the dimensions of interest to the scientist, and, unfortunately, the questioner may not always ask the follow-up question(s)
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From page 34... ...
. Until more is known, it should be clear that the pitch-matching and masking procedures described below should be done with headphones, not free-field presentations, so that there is at least the opportunity for the patient and the examiner to detect different origins for different aspects of the tinnitus.
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From page 35... ...
Further, in the best of circumstances, pitch matching is a difficult task even for highly practiced subjects, let alone for relatively inexperienced patients. In both populations, it is common to see so-called octave errors -- settings for a match that are actually twice or one-half the frequency of the sound being matched (see Vernon, 1977)
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From page 36... ...
Nearly all tinnitus sufferers comment on the fluctuating nature of their perception, but it seems safe to assert that few investigators realized that it varied so much in frequency. If it does, it has obvious implications for the design of tinnitus maskers/instruments (see "Tinnitus Maskers/Instruments" in Chapter 4)
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From page 37... ...
Apparently he saw this contralateral masking effect most regularly with Meniere's and sudden deafness patients, but it was also present in presbycusic and noise trauma patients. Note that a contralateral masking effect can be explained in a least two ways:
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From page 38... ...
The tinnitus was viewed as a signal, and each of a set of pure-tone maskers was adjusted in turn until it "just masked" the tinnitus. When the signal is an external tone, the pattern of masker intensities obtained with such a procedure has a characteristic shape (see Small, 1959)
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From page 39... ...
m is masking procedure has the virtue of providing a relatively precise estimate of the spectral locus of the tinnitus -- be it tonal or narrowband -- but it has the drawback of being relatively time-consuming and thus may not see wide application clinically. Relevant to the come mon assertion that tinnitus magnitude fluctuates greatly is the observation by Formby and Gjerdingen that substantially different masker levels were necessary in different sessions to mask the tinnitus.
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From page 40... ...
would decline with time, but because both masker and signal were being about equally affected, the noise intensity for equal masking would stay about the same. mat the intensity does not remain the same when masking the tinnitus implies either that external sounds and peripheral tinnitus do not affect primary fibers in the same way or that in these subjects the tinnitus is originating at a site beyond the (adapting)
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From page 41... ...
The resulting pair of cutoff frequencies-the "masking interval" -- is taken as the bandwidth of the tinnitus. As noted above, the possibility of binaural tinnitus that is not spectrally or Qualitatively similar in the two ears points out the need for masking measurements to be made using headphones, with monaural presentations made first to one ear and then the other, while the contralateral ear receives a broadband masker of reasonable intensity.
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From page 42... ...
Many auditory scientists believe that a more direct measure of tinnitus magnitude is obtained from loudnessmatching procedures (see Scharf, 1983) than from masking procedures.
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From page 43... ...
Since it is not possible to interrupt the continuous (say) monaural tinnitus when the matching sound is presented, the situation is analogous to the task known as the simultaneous binaural loudness balance, which has been controversial over the years just because of this uncertainty about the stimulus basis for the subjects' responses (see Elliott and Fraser, 1970; Scharf, 1983)
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From page 44... ...
or less to match the loudness of their tinnitus, and only 5 percent needed more than 30 dB SL. While this widely cited survey is informative, interpretation of the data is hampered by obstacle 5 noted above; namely, when there are intermural differences in audibility in the spectral region of the tinnitus and the match is reported in terms of SL in the contralateral ear, there is necessarily uncertainty about the actual intensity needed for the match.
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From page 45... ...
The barely audible crinkling of a cellophane candy wrapper can be highly distracting and annoying even during the loudest segment of a concerto with full orchestra. Beyond everyday examples, the noncorrespondence between physical and psychophysical measures of sound and its capacity to annoy has long plagued scientists interested in quantifying annoyance (see, for example, Fidell, 1978; Schultz, 1978)
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From page 46... ...
More recent discussions of the discrepancy between the apparent magnitude and the annoyance of tinnitus have tried to emphasize the possibility of a basis for the effect other than a "psychological" one. The reader should recall here that tinnitus magnitude is typically reported in units of SL -- decibels above the subject's own absolute threshold at that frequency.
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From page 47... ...
Whatever the eventual neurophysiological explanation of this effect it is clear that the tinnitus is behaving aberrantly. Expanding on the comment of Penner et al., it may be that this and other aberrant behaviors "bring the tinnitus to the attention" of certain neural mechanisms that persist in unsuccessful attempts to force the tinnitus to conform to the behavior of external sounds and that their ongoing failure reaches consciousness as annoyance.
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From page 48... ...
It is believable that the feeling of helplessness induced by this lack of control over their tinnitus is an important contributor to the annoyance reported by many tinnitus sufferers. In summary, when attempting to comprehend the annoyance I S THE TINNITUS MONAURAL OR BINAURAL ?
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From page 49... ...
When external sounds that are similar spectrally and equal in intensity are presented to the two ears, the phenomenological experience is of a single fused image located in the center of the head. (In everyday listening, of course, sounds correctly appear to originate outside the head from locations in auditory space, but, with headphone listening and with self-generated sounds such as tinnitus, the sounds appear to originate from a location somewhere within the head; this difference between localization and lateralization, respectively, has never been fully explained -- but see Schroeder [1975]
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From page 50... ...
Once a subject has matched his or her tinnitus for center frequency, complexity, and intensity, a similar waveform -- but located in a spectral region adjacent to the tinnitus -- could be presented binaurally and the subject asked to adjust the intensity in the ear opposite the perceived tinnitus until the image of this external sound appeared to originate from the same intracranial location as the tinnitus. If the intensity difference required for this match is small, it would be evidence for a binaural origin of the tinnitus; if it is relatively large, or if the patient is satisfied with a match to a monaural stimulus, it would argue for a monaural origin.
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From page 51... ...
For example, he found combinations of frequency and intensity of the external tone that should have produced beats but that instead produced "complete silence. n Over the years, Wegel's report has been widely cited, but it has generally been viewed with skepticism and dismissed; however, recent developments have brought new attention and credibility to it.
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From page 52... ...
Two external tones to different ears can produce beats -- they are called binaural beats -- but such beats are different from monaural beats in many ways. Of primary interest here is the fact that binaural beats cannot be produced above about 800-1000 Hz using a single pure tone to each ear (Licklider et al., 1950; Perrott and Nelson, 1969; but compare McFadden and Pasanen, 1975)
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From page 53... ...
. For external sounds, masking can only be accomplished by sounds within certain spectral regions surrounding the signal; those regions do increase with increasing masker intensity, but they never reach the point of being several octaves above or below the signal, as has sometimes been reported for tinnitus "masking" (Vernon and Meikle, 1981)
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From page 54... ...
. In itself this is not unlike the behavior of external sounds -- an external sound can mask a contralateral external signal via either crossconduction or central masking.
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