Data processing: speech signal processing – linguistics – language – Speech signal processing – Application
Reexamination Certificate
2000-02-02
2002-10-15
{haeck over (S)}mits, T{overscore (a)}livaldis Ivars (Department: 2654)
Data processing: speech signal processing, linguistics, language
Speech signal processing
Application
C340S407100, C607S056000
Reexamination Certificate
active
06466911
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to improvements in electrotactile vocoders.
BACKGROUND OF THE INVENTION
Hearing impairment limits access to speech cues and other acoustic information. The degree and ability of patients to use any residual hearing will determine how much the hearing-impaired person is able to understand using hearing aids. Most people with a significant hearing loss will need to use lip-reading to gain further speech information. Some cues to speech, such as place of consonant articulation, are relatively visible, however other speech cues, such as the formants of back vowels, and in particular consonant voicing, cannot be distinguished using visual cues. The role of tactile devices is to provide supplementary information which the hearing-impaired person can add to the visual and auditory information they receive. Tactile devices do not function as a complete speech information channel, and the wearer must continue to use visual and any available auditory information to maximise speech understanding.
Tactile devices provide speech information through electrotactile or vibrotactile stimulation of the tactile sense. Electrotactile devices use electrodes and low level electric current to stimulate the nerves endings of the tactile sense. Vibrotactile devices use vibrators to stimulate the tactile sense. Two different types of approaches may be employed to present speech information via tactile devices. The speech processing approach involves the tactile device selecting from the speech input certain aspects of the speech which are considered to be important for understanding the message. Alternatively, the bandpass approach involves filtering the entire speech input into a number of bands which are defined by frequency boundaries.
Many different body sites have been employed for use with tactile devices, some of the most common are the forearm, wrist, stomach, sternum and fingers. The transducers are usually held firmly against the skin—using elastic straps or a type of handset. See for example U.S. Pat. No. 4,982,432 (Clark et al) and U.S. Pat. No. 5,035,242 (Franklin et al). In general the user must also wear a microphone and a box which contains the speech processor or filter for the speech input, the stimulator circuitry and the power supply.
In our U.S. Pat. No. 4,982,432, in particular, the entire contents of which are incorporated herein by cross-reference, we have disclosed an electrotactile vocoder which has been found to assist severely and profoundly deaf adults, as well as providing assistance to speech perception and to articulation when used as a self-feedback device. Information provided through the tactile sense can be used directly, or combined with information provided through other sense modalities, such as vision (speech reading) or audition (hearing aids).
Trials of the electrotactile vocoder described in the above United States patent have been undertaken, and these trials have clearly established that the device can provide assistance to speech perception, and to articulation to persons having hearing impairment.
The electrotactile vocoder described in the above US patent comprises two main component elements:
(i) a handset and associated cabling, which incorporate eight electrodes positioned over the digital nerve bundles on each side of the four fingers of one hand, the purpose of which is to transmit the electrically-encoded speech information to the user; and
(ii) a speech processor/stimulator unit and associated input microphone and cabling; the purpose of which is to detect incoming speech information, analyse and process this information, extract certain specific speech feature components as directed by the speech processing program implemented, electrically encode this information as changes in the stimulus electrical parameters of electrode selected, stimulus pulse width, and stimulus pulse rate, and send the electrical stimulus to the electrode handset for delivery to the user.
The trials referred to above have established that the electrotactile vocoder described in the above United States patent needed improvement in the following areas:
(i) the design of the electrotactile handset through which information is transmitted to the user and particularly the use of a large return electrode at the wrist;
(ii) the design of the speech processing strategy which is used to encode speech information for the user;
(iii) the circuitry and method of providing the electrical stimulus to the user, including the need for a large return electrode at the wrist, and for programming of the speech processor.
SUMMARY OF THE INVENTION AND OBJECT
It is the object of the present invention to provide improvements in electrotactile vocoders of the type described in the above US patent to thereby improve the ability of the electrotactile vocoder to provide benefit to hearing-impaired persons.
In a first aspect, the invention provides an electrotactile vocoder including a handset carrying stimulating electrodes which are positioned by the handset when worn to be in electrical contact with the fingers to facilitate stimulation of the digital nerves of the user, a speech processor/stimulator unit for producing electrical stimulus at the electrodes based on incoming speech and other information, said stimulator including circuit means for applying stimulating current to said electrodes and for switching at least selected ones of said electrodes to a non-active state when stimulating current is applied to any one of the other electrodes, and means for utilising the electrodes in said non-active state as ground or return electrodes.
By adopting the above strategy, the wrist electrode described in the United States patent referred to above is no longer required thereby substantially increasing the ease of use of the device, including the ability to provide an essentially one-piece handset which may be conveniently used by the hearing-impaired person and overcoming the electrophysiological problem of dielectric breakdown at the wrist electrode, which causes unpleasant levels of stimulation at the large return electrode under specified conditions, including dry climates.
In a preferred form, all electrodes which are in said non-active state are utilised as ground or return electrodes.
In another aspect, the invention provides an electrode handset for an electrotactile vocoder, including a body, four finger members extending outwardly from said body, each finger member having a shaped opening for receiving a finger and defining a ring-like member encircling the finger while leaving the fingers substantially free, opposed pairs of electrodes positioned adjacent each opening so as to make electrical contact with opposite sides of each finger in the region of the digital nerve when the fingers are inserted into the finger openings of the finger members, said ring-like members holding said electrodes in electrical contact with said fingers while allowing flexing of the hand or fingers without substantially affecting said electrical contact, said body also including an opening defining a wrist engaging strap for holding the handset on a hand with said electrodes engaging said fingers.
The body is most conveniently made of a resilient material, such as neoprene, and conductive wires extend from the electrodes to an electrical connector adapted for connection to the speech processor/stimulator of an electrotactile vocoder.
The wires are preferably mounted on the surface of the electrode handset body and may be retained in position by an adhesive overlay or any other suitable means. In this way, the wiring is integrated into the body of the handset thereby reducing the likelihood of dielectric breakdown while ensuring a pleasant and effective stimulus delivered through the electrodes.
The speech processor/stimulator unit also incorporates a speech processing strategy which modifies the strategy utilised in the case of the electrotactile vocoder described in the above US Patent. In that strategy which was based on the multichannel cochlear implant developed b
Cowan Robert S C.
Galvin Karyn L.
Lu Bich D.
Millard Rodney E.
Nixon & Vanderhye
The University of Melbourne
{haeck over (S)}mits T{overscore (a)}livaldis Ivars
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