Tinnitus rehabilitation device and method Number:7,520,851 from the United States Patent and Trademark Office (PTO) owispatent

Title: Tinnitus rehabilitation device and method

Abstract: A tinnitus method and device for providing relief to a person suffering from the disturbing effects of tinnitus is described. The method can be implemented entirely in software to spectrally modify an audio signal in accordance with a predetermined masking algorithm which modifies the intensity of the audio signal at selected frequencies. A predetermined masking algorithm is described which provides intermittent masking of the tinnitus wherein, at a comfortable listening level, during peaks of the audio signal the tinnitus is completely obscured, whereas during troughs the perception of the tinnitus occasionally emerges. In practice it has been found that such intermittent masking provides an immediate sense of relief, control and relaxation for the person, whilst enabling sufficient perception of the tinnitus for habituation and long term treatment to occur. Advantageously the predetermined masking algorithm is specifically tailored to the audiometric configuration of the person. For example, the masking algorithm may be partly tailored to the hearing loss characteristic of the person. A tinnitus rehabilitation device used in conjunction with a personal sound reproducing system is also described.

Patent Number: 7,520,851 Issued on 04/21/2009 to Davis,   et al.

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Inventors:	Davis; Paul B. (Fremantle, AU), James; Lachlan S. (Turramurra, AU), McSweeney; Benjamin A. (Cheltenham, AU), Laidlaw; Linda E. (Marsfield, AU), Frater; Robert H. (Lindfield, AU), Hanley; Peter J. (Naremburn, AU)
Assignee:	Neurominics Pty Limited (Chatswood, New South Wales, unknown)
Appl. No.:	10/727,036
Filed:	December 4, 2003

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Related U.S. Patent Documents

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	Application Number	Filing Date	Patent Number	Issue Date
	09936687		6682472
	PCT/AU00/00207	Mar., 2000

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Foreign Application Priority Data

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Mar 17, 1999 [AU]			PP9275

Current U.S. Class:	600/25
Current International Class:	H04R 25/00 (20060101)
Field of Search:	600/23-27 128/864,897-899 381/312-315,320-321,124 607/55-57

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References Cited [Referenced By]

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Other References

Sony, User and Service Manual for Models TCD-D8 and D-171, 1995 and 1996. Available at www.sony.net and www.sony.com. cited by examiner . Vernon et al. "Tinnitus masking: Unresolved Problems" Tinnitus (1981) 239-262. cited by other . Al-Jassim, A. H. "The use of Walkman mini-stereo system as a tinnitus masker" Journal of Laryngology and Otology (Jan. 1988) vol. 102, 27-28. cited by other . International Search Report for related International Application No. PCT/AU2004/001700 dated Feb. 1, 2005. cited by other . Australian Search Report and Written Opinion for related Application No. SG 20063732-9 dated Apr. 21, 2008. cited by other . First Office Action for related Chinese Application No. 200480041291.3 dated Oct. 26, 2007. cited by other . Office Action for related Japanese Application No. 2000-605446 dated Dec. 4, 2007. cited by other.

Primary Examiner: Gilbert; Samuel G
Attorney, Agent or Firm: Jones Day

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Parent Case Text

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CROSS-REFERENCE TO RELATED APPLICATIONS

This Application is a Continuation-In-Part of U.S. application Ser. No. 09/936,687, filed on Sep. 17, 2001, which is the national stage of International Application No. PCT/AU00/00207, filed on Mar. 17, 2000, which designates the United States. These applications, in their entirety, are herein incorporated by reference.

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Claims

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What is claimed is:

1. A device for providing treatment of an auditory system disorder comprising: a computer readable medium storing a treatment signal; an output for outputting the signal for treating the auditory system disorder; a processor configured to reset the volume of the treatment signal to a minimum non-zero value and below a volume for intermittently or fully masking the auditory system disorder between each treatment session; and a volume adjusting feature that is configured to allow the patient to adjust the volume of the treatment signal at the beginning of each treatment session to intermittently or fully mask the auditory system disorder.

2. The device as claimed in claim 1, wherein the auditory system disorder is tinnitus and the treatment signal is a highly dynamic masking signal whose spectral content and intensity constantly varies over time.

3. The device as claimed in claim 1, wherein the auditory system disorder includes conditions of sound loudness discomfort such as hyperacusis.

4. The device as claimed in claim 1, further comprising a compliance monitoring device for allowing a patient to monitor how much time the patient has used the device during a fixed time period.

5. The device as claimed in claim 1, further comprising a battery for supplying power to the device with sufficient battery life to allow extended use without recharging.

6. The device as claimed in claim 5, wherein the battery has a life approximately equivalent to at least one week of treatment.

7. The device as claimed in claim 1, wherein the computer readable medium has a storage capacity sufficient to provide a choice, range, or diversity of treatment signals.

8. The device as claimed in claim 7, wherein the computer readable medium storage capacity is approximately equivalent to 4 hours of the treatment signal.

9. The device as claimed in claim 1, further comprising a safety locking function for preventing a patient from using the device if the computer readable medium does not contain the patient's treatment signal.

10. The device as claimed in claim 1, further comprising coding of the treatment signal, for example by encryption, so as to prevent use of a corrupted or otherwise modified audio signal.

11. The device as claimed in claim 1, further comprising a patient identification code in order to allow correct identification of the patient's own device.

12. The device as claimed in claim 1, further comprising a data downloading function for downloading logged information, wherein the logged information contains information relating to the patient's use of the device.

13. The device as claimed in claim 12, wherein the data downloading function is performed by at least one of a wired interface, an infrared interface, or a wireless interface.

14. The device as claimed in claim 1, wherein the processor is configured to reset the volume of the treatment signal to a volume that is selected based on a patient profile.

15. The device as claimed in claim 1, wherein the processor is configured to reset the volume of the treatment signal to a volume that is just audible by the patient.

16. A device for providing treatment of an auditory system disorder comprising: a computer readable medium for storing a treatment signal; an output for outputting the signal for treating the auditory system disorder; a volume adjusting feature; and a safety locking function for preventing a patient from using the device if the computer readable medium does not contain the patient's treatment signal.

17. The device as claimed in claim 16, wherein the auditory system disorder is tinnitus and the treatment signal is a highly dynamic masking signal whose spectral content and intensity constantly varies over time.

18. The device as claimed in claim 16, further comprising a battery for supplying power to the device with sufficient battery life to allow extended use without recharging.

19. The device as claimed in claim 18, wherein the battery has a life approximately equivalent to at least one week of treatment.

20. The device as claimed in claim 16, wherein the computer readable medium has a storage capacity sufficient to provide a choice, range, or diversity of treatment signals.

21. The device as claimed in claim 20, wherein the computer readable medium storage capacity is approximately equivalent to 4 hours of the treatment signal.

22. The device as claimed in claim 16, further comprising a compliance monitoring device for allowing a patient to monitor how much time the patient has used the device during a fixed time period.

23. The device as claimed in claim 16, further comprising coding of the treatment signal, for example by encryption, so as to prevent use of a corrupted or otherwise modified audio signal.

24. The device as claimed in claim 16, further comprising a patient identification code in order to allow correct identification of the patient's own device.

25. The device as claimed in claim 16, further comprising a data downloading function for downloading logged information, wherein the logged information contains information relating to the patient's use of the device.

26. The device as claimed in claim 25, wherein the data downloading function is performed by at least one of a wired interface, an infrared interface, or a wireless interface.

27. The device as claimed in claim 16, wherein the auditory system disorder includes conditions of sound loudness discomfort such as hyperacusis.

28. A device for providing treatment of tinnitus comprising: a signal filtering means configured to generate a treatment signal with peaks and troughs by spectrally modifying at least a portion of an input signal to account for the basic audiometric configuration of a person; an output for outputting the signal for treating the tinnitus; a processor configured to reset the volume of the treatment signal to a minimum non-zero value and below a volume for intermittently or fully masking the tinnitus between each treatment session; and a volume adjusting feature that is configured to allow the patient to adjust the volume of the treatment signal at the beginning of each treatment session to intermittently or fully mask the tinnitus.

29. The tinnitus treatment device as claimed in claim 28, wherein the signal filtering means accounts for a person suffering from conditions of sound loudness discomfort such as hyperacusis.

30. The device as claimed in claim 28, further comprising a compliance monitoring device for allowing a patient to monitor how much time the patient has used the device during a fixed time period.

31. The device as claimed in claim 28, further comprising a battery for supplying power to the device with sufficient battery life to allow extended use without recharging.

32. The device as claimed in claim 31, wherein the battery has a life approximately equivalent to at least one week of treatment.

33. The device as claimed in claim 28, further comprising a computer readable medium having a storage capacity sufficient to provide a choice, range, or diversity of treatment signals.

34. The device as claimed in claim 33, wherein the computer readable medium storage capacity is approximately equivalent to 4 hours of the treatment signal.

35. The device as claimed in claim 28, further comprising a computer readable medium and a safety locking function for preventing a patient from using the device if the computer readable medium does not contain the patient's treatment signal.

36. The device as claimed in claim 28, further comprising coding of the treatment signal, for example by encryption, so as to prevent use of a corrupted or otherwise modified audio signal.

37. The device as claimed in claim 28, further comprising a patient identification code in order to allow correct identification of the patient's own device.

38. The device as claimed in claim 28, further comprising a data downloading function for downloading logged information, wherein the logged information contains information relating to the patient's use of the device.

39. The device as claimed in claim 38, wherein the data downloading function is performed by at least one of a wired interface, an infrared interface, or a wireless interface.

40. The device as claimed in claim 28, whereby, when the treatment signal is heard by the person at a comfortable listening level, during the peaks, the tinnitus is substantially completely obscured and the person perceives significant masking of the tinnitus, and during troughs, the person may occasionally perceive the tinnitus.

41. The device claimed in claim 28, wherein the processor is configured to reset the volume of the treatment signal to a volume that is selected based on a patient profile.

42. The device as claimed in claim 28, wherein the processor is configured to reset the volume of the treatment signal to a volume that is just audible by the patient.

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Description

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BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a tinnitus rehabilitation device and a method for providing relief and treatment to persons suffering from the disturbing effects of tinnitus. More particularly, though not exclusively, the present invention relates to such a method and device that employs intermittent masking of the tinnitus.

2. Description of Related Art

Tinnitus is the perception of a sound in the absence of any corresponding external sound. It is most commonly perceived as a ringing, buzzing, whirring type sound, but can also be perceived as a beating, or pounding sensation. Approximately one third of the people who suffer from tinnitus can be highly disturbed by it. Continuous perception of tinnitus can lead to insomnia, an inability to relax, state and trait anxiety, depression, and even suicide in extreme cases. Often closely associated with tinnitus is the perception of hyperacusis, which is a great intolerance to external sounds, even the softer everyday sounds. This distressing condition can even occur as a precursor to tinnitus, and is thought to share the same underlying causes. Thus, every reference to tinnitus in this document should be construed as including the phenomena of hyperacusis or other types of loudness discomfort.

There are very few effective treatment options available for tinnitus sufferers, with the vast majority only being advised that "you'll have to learn to live with it". Most patients find that they can far more readily ignore an external sound than their tinnitus. One palliative method has been to use hearing aid-style devices that produce a band of noise to totally mask the perception of the tinnitus. A variety of such devices have been described, including a tinnitus masker that produces sounds of from 1,000 Hz to 5,000 Hz (U.S. Pat. No. 4,222,393), a patient-controlled master hearing aid (U.S. Pat. No. 4,759,070), a masker that produces a sound spectrum containing a line spectrum with a fundamental tone that is adjustable from 125 Hz to 20,000 Hz (U.S. Pat. No. 5,167,236), a masker whose output slowly cycles through a frequency range (U.S. Pat. No. 5,325,827), a masker with a bandwidth selector function (U.S. Pat. No. 5,403,262), a masker comprising a frequency response analyzer and shaping apparatus (U.S. Pat. No. 5,663,727). Such masking can give a sense of relief and control over the tinnitus in up to half of patients, but usually has no long-term effect. The prohibitive cost and aesthetic considerations limits the proportion of sufferers for whom this is a viable measure. The presence of hearing loss for external sounds in the tinnitus region often means that the masking noise needs to be unpleasantly loud before the tinnitus can be masked, and the noise is often judged to be not much better than the tinnitus itself.

Other reported devices attempt to achieve masking using devices that deliver vibrations (U.S. Pat. No. 5,692,056), pulsed ultrasonic stimulation (U.S. Pat. No. 6,394,969) or radio frequency waves (eg. "Theraband..TM.") to the patient, while other reported devices (eg. U.S. Pat. No. 5,697,975) seek to achieve stimulation through direct electrical discharge to the brain. Yet another seeks to provide relief by delivering an acoustic stimulus at a level that is inaudible to the patient (PCT WO 0170110).

Over the past decade, a new understanding of the neurophysiological processes underlying tinnitus has been published, emphasizing the role of the neural pathways in the emergence of distressing tinnitus and the possibility of using this neural plasticity to retrain its perception. This has been dubbed "Tinnitus Retraining Therapy" or TRT. In this technique, patients are given intensive counseling, and use noise generators at a volume that does not completely mask the tinnitus. Long term reductions in tinnitus disturbance have been achieved in some patients, but it is usual for this process to take at least 18 months of therapy before any substantial benefit occurs. TRT also offers very little immediate sense of relief from the tinnitus, and no relief from the associated sleep disturbance and inability to relax.

The closest known prior art to the invention is the "Silentia Set" developed by Starkey Corp., which is a pair of hearing aid devices which wirelessly receive signals from a stereo system via an induction loop under a pillow at bedtime. Recording of high frequency noise bands ("water sounds"), babble noise, traffic sounds and music have been used to mask tinnitus using this system, however the high cost of the Silentia Set make it prohibitive for many sufferers.

Other prior art audiotherapeutic techniques using music are the Tomatis Method developed by Alfred A. Tomatis, and Auditory Integration Training. While neither method is designed for the treatment of tinnitus, the two techniques have some similarities in that they modify music for the treatment of auditory disorders. The Tomatis Method employs an "Electronic Ear" developed by Alfred Tomatis, (U.S. Pat. No. 4,021,611). It has its origins from an extremely outdated model of how the auditory system works, and has been widely debunked by audiological organizations. Auditory Integration Training is based on the Tomatis Method, but presents the music at extremely loud levels, that may result in hearing damage, and importation of devices using this technique have been banned by the American Food and Drug Administration.

BRIEF SUMMARY OF THE INVENTION

The present invention was developed with a view to providing a more effective rehabilitation technique and device for tinnitus sufferers that is consistent with contemporary understandings of the underlying pathology in the auditory system, of which tinnitus is a symptom.

Throughout this specification the term "comprising" is used inclusively, in the sense that there may be other features and/or steps included in the invention not expressly defined or comprehended in the features or steps subsequently defined or described. What such other features and/or steps may include will be apparent from the specification read as a whole.

According to an aspect of the present invention there is provided a tinnitus rehabilitation method for providing relief to a person suffering from the disturbing effects of tinnitus, comprising: providing an audio signal spectrally modified in accordance with a predetermined masking algorithm designed to modify the intensity of the audio signal at selected frequencies whereby, in use, when the spectrally modified audio signal is heard by the person it provides significant masking of the tinnitus.

The method may further comprise: transmitting, using a computer, data representing an audiogram of the person suffering from tinnitus; processing the audiogram data at a remote location and producing required equalization response data based on the audiogram data using the predetermined masking algorithm; receiving, using a computer, the required equalization response data; and, combining the required equalization response data with audio data representing the audio signal to produce the spectrally modified audio signal.

According to another aspect of the invention there is provided a method of using a computer to provide access to a predetermined masking algorithm used in tinnitus rehabilitation, for providing relief to a person suffering from the disturbing effects of tinnitus, comprising: receiving on-line, from a user, data representing an audiogram of the person suffering from tinnitus; processing the audiogram data using the predetermined masking algorithm to produce required equalization response data based on the audiogram data; and, transmitting the required equalization response data to the user.

According to another aspect of the present invention there is provided a tinnitus rehabilitation sound recording for providing relief to a person suffering from the disturbing effects of tinnitus, comprising: an audio signal spectrally modified in accordance with a predetermined masking algorithm designed to modify the intensity of the audio signal at selected frequencies whereby, in use, when the sound recording is heard by the person it provides significant masking of the tinnitus.

The predetermined masking algorithm may provide intermittent masking of the tinnitus wherein, at a comfortable listening level, during peaks of the audio signal the tinnitus is substantially completely obscured, whereas during troughs the perception of the tinnitus occasionally emerges. In practice it has been found that such intermittent masking can provide an immediate sense of relief, control and relaxation for the person, whilst enabling sufficient perception of the tinnitus for habituation and long term treatment to occur.

The predetermined masking algorithm may be designed to modify the intensity of the audio signal across substantially the full spectral range of the audio signal. The audio signal may be a highly dynamic signal in which the spectral content and intensity constantly varies over time. The audio signal may be a music signal. However other types of signals including speech or noise might also be employed.

The predetermined masking algorithm may be at least partly tailored to the audiometric configuration of the person. The predetermined masking algorithm may be partly tailored to the hearing loss characteristic of the person. The spectral qualities of the audio signal may be modified by the masking algorithm so as to provide a relatively equal sensation level across a major portion of the audio spectrum in both ears. The predetermined masking algorithm may also incorporate a set of calibration figures such as for converting dB HL (Hearing Level) to dB SPL (Sound Pressure Level), or to correct for the presence of various coupling system types.

According to another aspect of the present invention there is provided a tinnitus rehabilitation device for providing relief to a person suffering from the disturbing effects of tinnitus comprising: signal filtering means adapted to spectrally modify an audio signal in accordance with a predetermined masking algorithm designed to modify the intensity of the audio signal at selected frequencies whereby, in use, when the spectrally modified audio signal is heard by the person it provides significant masking of the tinnitus.

The signal filtering means may be a programmable signal filtering means whereby, in use, the device can be programmed with a predetermined masking algorithm adapted to the particular needs of the individual suffering from tinnitus.

In an embodiment of the device the predetermined masking algorithm is of the form: REQ=M(SPL+ELC(0.25, 0.5, 1, 2, 3, 4, 6, 8, 10, 12 kHz)-Baseline) Where: REQ=Required equalization response of the Tinnitus Retraining Protocol Baseline=0.5(A-B)+B A=mean dB SPL at the two adjacent greatest hearing loss frequencies in the greatest hearing loss ear B=mean dB SPL at the two adjacent least hearing loss frequencies in the least hearing loss ear SPL=hearing thresholds (in dB HL) converted to dB SPL ELC=transfer values for 40 Phon Equal Loudness Contours M=gain multiplier=0.3 to 0.95, and Preferably M=0.4

However, in an alternative software embodiment of the invention, the mathematical algorithm by which the individual prescription of the audio signal is calculated may differ from the above algorithm. Such other embodiments of the invention would be consistent with the essential clinical technique that is intended to provide a modification of the intensity of an audio signal to account for hearing levels specifically for the relief and/or treatment of tinnitus and hyperacusis.

The device may be employed in conjunction with a personal music player (PMP) and has an input adapted to connect to the audio output headphone jack on the PMP. The device may have a standard headphone jack to which a standard PMP headphone can be connected. Alternately, a transmitter may be used to transmit a signal to a wireless type of receiver that may be placed in the ear canal, concha area, behind the ear, or some other area relatively close to the ear.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to facilitate a more detailed understanding of the nature of the invention preferred embodiments of the tinnitus rehabilitation device and method will now be described in detail, by way of example only, with reference to the accompanying drawings in which:

FIG. 1 is a graphical representation of the long-term spectra of both a music recording and a typical prior art tinnitus masker;

FIG. 2 is a graphical representation of a typical patient's hearing thresholds and their required equalization curve calculated using a first embodiment of the masking algorithm;

FIG. 3 is a schematic diagram graphically illustrating intermittent tinnitus masking with music;

FIG. 4 is a graphical representation of the same patient's hearing thresholds and their required equalization curves calculated using a second embodiment of the masking algorithm;

FIG. 5 is a schematic block diagram of a possible embodiment of a tinnitus rehabilitation device in accordance with the invention;

FIGS. 6A-E and 7A-E are flowcharts illustrating a preferred method of providing a tinnitus rehabilitation sound recording in accordance with the present invention, and

FIG. 8 is a schematic diagram of an embodiment of a tinnitus rehabilitation method.

FIG. 9 is a schematic diagram of an embodiment of a tinnitus rehabilitation device.

DETAILED DESCRIPTION OF THE INVENTION

Tinnitus masking can be broadly defined as the obscuring of tinnitus perception with an external sound. Hearing aids can provide an effective form of environmental noise masking for only around 10% of sufferers. The most reliable audiometric measure of the effectiveness of tinnitus maskers is the amount of noise required to just mask an individual's tinnitus. This measure is known as the Minimum Masking Level ("MML"). Amongst the most important criteria for successful masking is that the acceptability of a masking stimulus is inversely proportional to its MML, and that the stimulus needs to be a sufficiently pleasant substitute for the tinnitus. In the present inventor's clinical practice, several sufferers have reported attempting to use music to find relief from their tinnitus, but often found that the volume required to mask their tinnitus was unacceptably high. Most of these persons tended to have a steeply sloping hearing loss characteristic, and a tinnitus pitch which closely corresponded with the edge of the maximal hearing loss frequencies. One of the reasons why previous attempts at using music have not always been successful may be the extremely high co-morbidity of high frequency hearing loss with tinnitus.

Typically, the presence of a sloping high frequency hearing loss would mean that at a relaxing sound volume level, only the low pitch components of the music are heard, and therefore the perception of any musicality and high frequency available for masking is inhibited. The long term spectra of both a music recording and a typical prior art tinnitus masker (a Starkey TM5) are illustrated in FIG. 1. A sound level analyzer was used to average the response of each of the two recordings over a 64 second period. The spectra were then matched at 1 kHz to enable a comparison of the frequency composition of the two spectra, irrespective of overall sound pressure levels. As can be seen from FIG. 1, if the masker is assumed to be the optimal frequency response for hearing impaired listeners, then the unfiltered music has insufficient high frequency energy and excessive low frequency response. Therefore, the present inventor has developed a tinnitus masking protocol which modifies the frequency response characteristics of an audio signal with a view to overcoming some of the shortcomings of traditional tinnitus maskers.

Although the following description will be made primarily with reference to modifying the frequency response characteristics of music, it is to be understood that a tinnitus masking protocol in accordance with the invention may also be applied to other types of audio signal suitable for masking of tinnitus, or for providing auditory stimulation for tinnitus and hypercusis therapy without masking. The following description will give particular emphasis to the use of conventional, insert or wireless headphone systems or insert type headphones in conjunction with a suitable personal sound reproduction system such as a high fidelity personal music player (PMP) for audio cassette, CD, MP3, or WMA recordings. In Australia, the retail cost of a high fidelity PMP is around one-tenth the cost of conventional binaural maskers. However, it is to be understood that the tinnitus masking protocol according to the invention may also be applicable to conventional hearing aid-style maskers. The technique can also be applicable to the setting of additional user programs in hearing aids, or the modified signal may be transmitted to the tinnitus sufferer through their hearing aids' telecoil or induction coil facility.

In addition to the low cost and high portability of PMPs, they generally possess small headphones with long-throw transducers that enable far superior fidelity compared to most free field loudspeaker systems. Furthermore, headphones are generally more effective than loud speakers because they circumvent the extensive attenuation of high frequency sounds that occurs through a free field. Changes in PMP earphone position on the pinna have been shown to have very limited effects on the spectral composition of toned sweeps measured in a KEMAR (Knowles Electronic Mannequin for Acoustic Research).

In developing a tinnitus masking protocol, the required extended upper frequency stimulus presented challenges for the conversion of audiogram results to the required real ear response, given that there are as yet no internationally agreed-upon standards for the conversion between dB HL to dB SPL for 10 and 12 kHz pure tone and narrow band noise stimuli. The manufacturer's calibration specifications for a Madsen OB 822 audiometer were used to extrapolate the required values for use with a telephonics TDH 39 headphones and MX 41/AR cushions. The audiometer was professionally calibrated accordingly. The values for 10 kHz were 50 dB HL=59.5 dB SPL and at 12 kHz, 50 dB HL=61 dB SPL. All ISO hearing level frequencies below 10 kHz were calibrated as per the relevant Australian standards (AS 1591.2-1987). Table 1 lists the transfer/calibration values in inverted format used for converting dB HL to dB SPL.

TABLE-US-00001 TABLE 1 Frequency kHz 0.25 0.5 1 1.5 2 3 3 6 8 10 12 dB 25.5 11.5 7.0 6.5 9.0 10.5 10.5 16.5 12.0 9.5 11.0

A further feature of the first tinnitus masking protocol (TMP1) developed by the inventor, was an adaptation of the half gain rule, whereby amplification for hearing loss is most effective when it compensates for only around one half of the hearing deficit. This rule underlies most current hearing aid prescriptive practices. The TMP1 attempted to maximize the acoustic energy centered around the pitch of the individual's tinnitus, and to "balance" the headphone output to correct for any asymmetrical hearing loss. A further goal was to enable the balanced perception of the masking stimulus throughout the person's head, rather than at the ear level like traditional uncorrelated tinnitus maskers.

All PMPs have a volume control range that far exceeds what is available in hearing aids, and so the TMP1 did not need to specify absolute gain figures. However, PMPs generally do not possess a left/right balance control, and this was expected to reduce their acceptability in cases of asymmetrical hearing loss and its associated loudness recruitment. As the TMP1 formulae aimed to minimize the perceptual loudness of the music or noise required to mask an individual's tinnitus, it thus only needed to specify the relative frequency response characteristics for each ear when presented in those reproduction systems that do not provide individual control of each stereo channel.

The procedure for applying the TMP1 was thus as follows: (i) The individual's pure tone hearing level thresholds at each frequency were converted to dB SPL by the addition of the transfer values in Table 1. (ii) The tinnitus pitch match frequency in the most severely affected ear was chosen for the maximal point of the base line calculation. The two adjacent best hearing thresholds of the lesser hearing loss ear was always chosen as the minimum point of the calculation. When a reliable pitch match was not found using pure tones, it was substituted with the mean of the two adjacent best hearing frequencies. Thus, the base line constituted a mid line value between the two greatest audiometric extremities. (iii) The final equalization values were then derived by subtracting the base line from the hearing threshold (expressed in dB SPL) for each frequency and each ear. Thus the algorithm for patients whose tinnitus pitch could not be reliably determined was: Baseline=0.5(A-B)+B Required Equalization, REQ=0.5 {SPL(0.25, 0.5, 1, 2, 3, 4, 6, 8, 10, 12 kHz)-Baseline}

The algorithm for non-tonal tinnitus was: Baseline=0.5(C-B)+B REQ=0.5{SPL(0.25, 0.5, 1, 2, 3, 4, 6, 8, 10, 12 kHz)-Baseline} Wherein, A=hearing threshold (dB SPL) at frequency of tinnitus pitch match. B=mean dB SPL at the 2 adjacent least hearing loss frequencies. C=mean dB SPL at the 2 adjacent greatest hearing loss frequencies.

EXAMPLE 1

FIG. 2 is a graphical representation of the relationship between a typical individual's hearing levels, tinnitus and their required TMP1 equalization curves. This individual has a steeply sloping high frequency bilateral hearing loss and tinnitus at 10,000 Hz, both greater on the left side. Consequently, the required equalization curves revolve around the equalizer's baseline, achieving a partial correction for hearing loss by boosting the amount of high frequency gain and also correspondingly attenuating the low frequencies. As the hearing loss and tinnitus is worse on the left, that ear receives correspondingly greater amplification. Because of the abnormal growth of loudness perception which usually accompanies sensorineural hearing loss, (recruitment, and/or the presence of hyperacusis), complete correction for hearing levels is not provided, as this may exceed the individual's loudness discomfort levels.

A tinnitus rehabilitation sound recording was then produced on an audio cassette tape for use in the individual's PMP. A stereo frequency equalizer (Genexxa 31-9082) was used in this procedure, which includes ten adjustable frequency bands per channel, with centre frequencies at 0.031, 0.062, 0.125, 0.25, 0.5, 1, 2, 4, 8, 16 kHz. Each control had a range of + or -12 dB SPL. The equalizer featured an "EQ record" facility, so that the audio signal could be passed through the equalizer circuit before being recorded. The equalizer's controls for each of the ten frequency bands was set to the calculated values for the left ear in the left channel of the equalizer, and the right ear values set in the right channel, in accordance with the particular individual's equalization values as calculated by the TMP1 algorithm. The stereo output from a broadcast quality cassette recorder was connected to the stereographic equalizer, which then had its output routed to another high fidelity cassette deck for recording onto high fidelity audio cassette tape. Dual leads and stereo RCA connecters were used to preserve L/R channel separation.

Modified sound recordings of both music and white noise were made for use in clinical trials with 30 participants. Each participant was counseled as to the rationale behind masking therapy and the possible benefits of using the tinnitus rehabilitation sound recording. Each participant was issued with a new PMP with standard insert headphones (Sony MDR E552) that fit into the concha and thus do not require a headband. Sound level-peak analysis measures were then performed. With their custom-made tape playing in the PMP, they were asked to slowly turn up the volume until they could just no longer perceive their own tinnitus. This level was marked on the volume control wheel. Each participant was told to notify the audiologist if they subsequently needed to turn up the volume further than the marked position. They were encouraged to experiment downwards with the volume control over the course of each masking session, as they might find that they require progressively less volume to totally mask if residual inhibition occurred.

One group of participants was given a noise tape whereas the other group was given a music tape. While both treatment groups has similar levels of pre-therapy distress associated with their tinnitus, the music group displayed a much greater improvement by mid-therapy and these gains were maintained at the two-year post-therapy follow up. The noise group also displayed some improvement, but much less dramatic then the music group. 96% of the participants found their music or noise tapes to be an effective masker, which is a far higher acceptance rate than for conventional ear level tinnitus maskers.

In some cases, the TMP1 appeared to present an unbalanced perception of loudness where the individual possessed a substantial inter-aural asymmetry. The real-ear perception of loudness may have deviated from the prescribed response due to perception of loudness differences at various points across the frequency range. It was also thought that the half gain rule for hearing aids might be best suited for the moderate hearing loss population, and that a mild hearing loss might only require one-third gain. Furthermore, it is possible that the recruitment of loudness phenomena might be greater in tinnitus patients than non-tinnitus patients, particularly given its high co-morbidity with hyperacusis and phonophobia (the fear of external sounds). These factors suggested that the TMP1 might be over-compensating for hearing loss, and that further modifications were required to optimize the procedure.

The main purpose of the TMP1 algorithm was to produce an acceptable substitute for the tinnitus at the lowest possible MML and to accommodate for any interaural symmetries. However, it was subsequently realized that an improved masking algorithm would be more robust if the prescription of the required equalization response was performed solely on the basis of maximum and minimum hearing levels, and thereby attempt to provide relatively equal sensation levels at all frequencies. Data from the TMP1 study indicated that 44.4% of the music group, and 28.6% of the noise group participants preferred to set the volume of their audio tapes at a level which only partially masked their tinnitus. This occurred despite being instructed that the optimal setting was to totally mask. The differences in masking level preferences between the two types of stimuli also suggests that music was more acceptable than noise when used at volume levels where the tinnitus could still be partly perceived. Whilst the historical approach has been to totally mask tinnitus, and the current clinical trend is to partially mask, the present inventor has developed an improved tinnitus masking protocol based on intermittent masking. Since music is a highly dynamic signal, it appears possible that the intensity of music which partially masks might actually constitute a form of intermittent masking. A schematic representation of intermittent tinnitus masking using a music signal is illustrated in FIG. 3.

Without wishing to be bound by theory, it is believed that the intermittent masking of tinnitus with a relaxing stimulus (such as music) may be effective on a psychological, as well as on an acoustic or neural level. In theory, it is feasible that intermittent tinnitus masking with music might constitute a form of systematic desensitization. Whilst in a relaxed state, the listener might be alternatively perceiving, then not perceiving the tinnitus, according to the fluctuations in the peak levels of the music. The predictability of the music may mean that the tinnitus might not even be consciously perceived during the "troughs" of the music. Additionally, the tinnitus might "reappear" from the music often enough for habituation to occur. But the ongoing dynamic nature of the music signal prevents this limited exposure from being disturbing, and this may reduce any limbic system enhancement. Thus, the proposed intermittent-masking-with-relaxation-music technique may promote a synergetic effect through its additional mechanisms of facilitating a sense of control, a reduction in general anxiety levels, and a form of auto-hypnosis leading to a reduction of fear about the tinnitus itself. Therefore, an improved masking algorithm based on a tinnitus retraining protocol (TRP) was developed that was designed to produce intermittent masking of the tinnitus.

In practice, the TMP1 algorithm's use of the half-gain rule appeared to over-compensate for hearing loss as noted above, sometimes making the recording seem unbalanced or "tinny". Conversely, there were several factors that suggested that the one-third rule might not provide sufficient equalization. The long term music spectrum has considerably less high frequency energy than what is typically available from conventional tinnitus maskers, and yet the greatest hearing loss is typically concentrated in this region (see FIG. 1). Therefore, any substantial reduction of gain could prevent achieving adequate high frequency equalization to overcome the limitations in the music spectra and the effects of hearing loss. Therefore, because the half gain rule was sometimes excessive, but one third gain may be insufficient for the purposes of modifying music for long term tinnitus retraining, a medium was selected by the incorporation of a 0.4 gain multiplier, (M).

To further facilitate the provision of equal sensation levels of music across the full spectral range of the music signal, the improved TRP algorithm adopted the ISO Equal Loudness Contours (ELC). The ELC transfer values correct for any differences in loudness perception depending on the discreet frequencies (International Standards Association, 1961). The 40 phon contour curve was selected because the earlier study found that the mean participant's customized music recordings, under total masking conditions, displayed a RMS of 45.7 dB SPL. Thus, with 8 dB representing an approximate doubling of perceived loudness, 37.7 dB was extrapolated to be the midpoint between the threshold and total masking, and thus representative of the intensity around which intermittent masking would occur with those with a mild to moderate sloping hearing loss. The 40 phon contour was thus utilized because it was the closest to this mid point, and choice of the lower value curve also helped compensate for loudness recruitment.

The standard audiometric procedure is to obtain hearing thresholds using TDH 39 headphones, and the results are expressed in dB HL (Hearing Level). However, the convention for specifying hearing aid characteristics is to utilize dB SPL (Sound Pressure Level) values. Consequently the hearing thresholds (dB HL) obtained in the 6 cm.sup.3 headphones need to be converted into dB SPL by the addition of the transfer values in Table 1.

These transfer values were then summated with the 40 Phon contour values. The resulting transfer/calibration values are displayed in Table 2.

TABLE-US-00002 TABLE 2 Frequency kHz .25 .5 .75 1 1.5 2 3 4 6 8 10 12 Corrections 23.5 7.5 5.5 7 6.5 7 5.5 2.5 16.5 21 16.5 13

The tinnitus retraining protocol (TRP) algorithm is a modification of the TMP1 algorithm given above, and is as follows: REQ=0.4{ELC+SPL(0.25, 0.5, 1, 2, 3, 4, 6, 8, 10, 12 kHz)-Baseline} Where: Baseline=0.5(A-B)+B A=mean dB SPL at the two adjacent greatest hearing loss frequencies in the greatest hearing loss ear. B=Mean dB SPL at the two adjacent least hearing loss frequencies in the least hearing loss ear. SPL=hearing thresholds (in dB HL), converted to dB SPL. ELC=Transfer values for 40 Phon Equal Loudness Contours.

Alternatively, the patient's hearing thresholds may be obtained using 1/3 octave narrow band noises, and the gain multiplier (M) becomes 0.7 (or between the range of 0.5 to 0.95).

The procedure for applying the TRP was as follows: (i) The person's audiogram was perused to ascertain the two adjacent greatest hearing loss frequencies in the greatest hearing loss ear (A), and also the two adjacent least hearing loss frequencies in the least hearing loss ear (B). (ii) These four dB HL values were then converted to dB SPL by the addition of the transfer values in Table 1. (iii) The dB SPL mean of the two adjacent greatest hearing loss frequencies in the greatest hearing loss ear (A) was then calculated in dB SPL, and the procedure repeated for the two adjacent least hearing loss frequencies in the least hearing loss ear (B). (iv) A midline value was then calculated by the subtraction of B from A, which value is then halved, and the result added to the B value. This is the TRP baseline. (v) All of the dB HL thresholds from the audiogram were then added to the values in Table 2 above which is the summation of the ISO 40 Phon ELC correction values, and the dB HL to dB SPL transfer functions. This produces a measure of hearing in terms of the relative perceived loudness of stimuli at each of the discrete frequencies. The values were expressed in dB SPL so that the desired equalization frequency response could be determined within the 24 dB SPL range of the graphic equalizer. (vi) The baseline value was then subtracted from each transformed threshold, and its result then multiplied by the 0.4 gain rule. This process is repeated for each frequency of each ear. (vii) These values were then used to manually set the graphic equalizer with the left ear's required equalization response (REQ) used in the left channel, and the right ear's REQ used in the right channel of the equalizer.

EXAMPLE 2

The audiogram for the participant chosen to demonstrate how the TMP1 accounts for a steeply-sloping asymmetrical hearing loss (see Example 1 above), was also chosen to demonstrate how the TRP algorithm modifies the intensity of the audio signal at selected frequencies to provide intermittent masking of the tinnitus. Tables 3 and 4 below show the calculations at each frequency for the left and right ears respectively using the TRP algorithm above. The baseline calculation was made as follows:

.times..times..times..times..times..times..times..times..times..times..ti- mes..times..times..times..times..times..times..times..times..times..times.- .times..times..times..times..times..times..times..times..times..times..tim- es..times..times..times..times..times..times..times..times..times..times..- times..times..times. ##EQU00001##

TABLE-US-00003 TABLE 3 Corrections and Calculations ELC & SPL L. Freq P's P's transfer - (Hz) dB HL SPL functions = Baseline = .times.0.4 = REQ 250 5 23.5 28.5 47.625 -19.15 .times.0.4 -7.66 500 -10 7.5 -2.5 47.625 -50.15 .times.0.4 -20.06 750 2.5 5.5 8 47.625 -39.65 .times.0.4 -15.86 1000 15 7 22 47.625 -25.65 .times.0.4 -10.26 1500 25 6.5 31.5 47.625 -16.15 .times.0.4 -6.46 2000 40 7 47 47.625 -0.65 .times.0.4 -0.26 3000 65 5.5 70.5 47.625 22.85 .times.0.4 9.14 4000 60 2.5 62.5 47.625 14.85 .times.0.4 5.94 6000 60 16.5 76.5 47.625 28.85 .times.0.4 11.54 8000 60 21 81 47.625 33.35 .times.0.4 13.34 10000 80 89.5 16.5 96.5 47.625 48.85 .times.0.4 19.54 12000 80 91 13 93 47.625 45.35 .times.0.4 18.14

TABLE-US-00004 TABLE 4 Corrections and Calculations ELC & SPL L. Freq P's P's transfer - (Hz) dB HL SPL functions = Baseline = .times.0.4 = REQ 250 20 23.5 43.5 47.625 -4.15 .times.0.4 -1.66 500 -10 1.5 7.5 -2.5 47.625 -50.15 .times.0.4 -20.66 750 0 8.5 5.5 5.5 47.625 -40.12 .times.0.4 -16.85 1000 5 7 12 47.625 -35.65 .times.0.4 -14.26 1500 0 6.5 6.5 47.625 -41.15 .times.0.4 -16.46 2000 15 7 22 47.625 -25.65 .times.0.4 -10.26 3000 45 5.5 50.5 47.625 2.85 .times.0.4 1.14 4000 30 2.5 32.5 47.625 -15.15 .times.0.4 -6.06 6000 30 16.5 46.5 47.625 -1.15 .times.0.4 -0.46 8000 20 21 41 47.625 -6.65 .times.0.4 -2.66 10000 60 16.5 76.5 47.625 28.85 .times.0.4 11.54 12000 75 13 88 47.625 40.35 .times.0.4 16.14

The REQ equalization curves for both ears are illustrated graphically in FIG. 4. A comparison of FIG. 4 with FIG. 2 will confirm that the patient's right and left hearing thresholds [HTL (SPL)] curves are identical.

A second clinical study was conducted in which 90 people who suffer from tinnitus participated. The participants were allocated with block randomization into one of four treatment groups: one group to test a second generation total masking algorithm (TMP2), one to test the tinnitus retraining algorithm (TRP), one to empirically measure the current TRT approach of using low-level broadband noise stimulants, and a quasi-control group to receive counseling alone. The second study exceeded expectations, with dramatic levels of habituation experienced by more than three-quarters of the participants using spectrally modified music. The adoption of bibliotherapy and TRT-style counseling resulted in significant improvements in clinical outcomes for all treatment groups. However, counseling alone appeared to be insufficient treatment for most participants. An important finding was that the TRP group experienced the greatest mean improvements in tinnitus distress. The TMP2 stimulus group initially displayed a more rapid improvement, but the more gradual gains of the TRP group were sustained for longer, and ultimately were superior. There was little difference between the noise and counseling alone groups at post therapy and follow-up, although the mean improvements experienced by the counseling alone group were ultimately not statistically significant. While all treatment groups recorded mean reductions in tinnitus distress over therapy, the two music groups ultimately appeared to be the most effective. Approximately three-quarters of the two music group participants experienced significant habituation to their tinnitus (TMP2=78.6%, TRP=75%).

There were substantial reductions in hyperacusis scores for both music groups, and a slight reduction for the noise group. The group without acoustic stimulation (Counseling-only) displayed an increase in hyperacusis over the same period, strongly indicating that the provision of acoustic stimulation was a key ingredient in the hyperacusis improvements. The music group participants often reported that their hyperacusis levels tended to improve faster than their tinnitus perception.

The clinical studies therefore suggest that total masking with music is more effective to facilitate a rapid improvement in distress and relaxation levels, despite the fact that intermittent masking with music eventually proved to be more effective on several measures. This indicates that a two-stage approach might be most efficient, whereby patients initially should employ a total masking algorithm to give a stronger sense of relief and control, then later switch to intermittent masking to remove the tinnitus detection.

An embodiment of the