US 3566858 A
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United States Patent 72] Inventors Stephen R. Larson Evanston;
John C. Sinclair, Oak Park, Ill. 773,068
Nov. 4, l 968 Mar. 2, 1971 Zenith Radio Corporation Chicago, Ill.
[21 Appl. No.  Filed  Patented  Assignee [5 4] AN Tl-STUTTERING THERAPEUTIC DEVICE Audio An m1 n ier Pu 156 Shaping Circuit 23 Primary Examiner-Richard A. Gaudet Assistant Examinerl(yle L. Howell Attorney-John J. Pederson ABSTRACT: A therapeutic device which provides voice masking to assist a patient in overcoming a speech deficiency such as stuttering. A microphone, selectively responsive to the patients voice, receives his speech and converts it into electrical signals which are utilized to develop a control signal. An audio oscillator generates an audiofrequency pulsed wave which is varied in frequency in proportion to pitch changes in the patients voice by a circuit responsive to the control signal. An output transducer converts the audiofrequency pulsed wave into a corresponding sound wave which is applied to the patients ear. A switching circuit, also responsive to the control signal, enables application of the sound wave only while the patient is speaking or attempting to speak.
PATENTEU MAR 2 l97l Invenrors phen R. Larson John C. Sinclair AN TI-STUTTERING THERAPEUTIC DEVICE BACKGROUND OF THE INVENTION It is known that a persons speech deficiency, such as stuttering, is at least partially caused by the person hearing himself speak. Hence, devices to treat such a disorder have been developed which typically reduce the persons hearing response to his own voice by generating a masking signal. A conventional device of this nature uses a microphone to monitor the persons speech and develop a signal to trigger a soundproducing device to cause the latter to'deliver the masking signal while the person is speaking. Vented earpieces are used to couple the masking signal to the patients ear and permit him to hear others when he is not speaking. Thus, the person may use such a device and simultaneously carry on a normal conversation while he is overcoming his tendency to stutter.
The type of masking sound used in the conventional system may be a random sound also referred to as white noise. It is a sound composed of 'each frequency component in the audio frequency spectrum produced at random with approximately the same amplitude. Speech, on the other hand, is essentially composed of a fundamental frequency and higher harmonics thereof and occupies a relatively small portion of the audio frequency spectrum. Moreover, as the pitch of a persons voice changes so, naturally, does the fundamental frequency and its harmonics. Masking is accomplished by blocking the sound of the patients speech. In order to obtain sufficient amplitude for the frequency components of speech necessary to reduce a persons hearing response to his own voice and thereby obtain effective masking, a relatively large amplitude white noise signal is required. Thisnecessarily requires a large amount of amplification and, in the example of a wearable battery-operated device, greater battery drain and con- SUMMARY OF THE INVENTION In accordance with the invention, a new and. improved therapeutic system for assisting a patient to overcome a tendency to stutter, of the type comprising a microphone for monitoring the speech of the patient, a sound-producing device to be worn by the patient, and means for delivering a masking signal to the sound-producing device to cause the latter to reduce the patients hearing response to his own voice, comprises the improvement of providing means coupled to said microphone for effecting variations in the frequency of the masking signal in accordance with the variation in pitch of the patients voice.
BRIEF DESCRIPTION OF THE DRAWING The features of the present invention which are believed to be novel are set forth with particularity in the appended claims. The invention, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawing, the single FIGURE of which is a schematic diagram of a preferred embodiment of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the FIGURE, an improved antistuttering therapeutic device includes a microphone which preferably is selectively responsive only to speech sound waves from a patient using the device. These sound waves may be received by placing such a microphone near the patients throat, substernal triangle, or other portions of the body where speech vibrations are prevalent. Using a selective microphone substantially eliminates the possibility of extraneous noises interferring with the operation of the device.
In general, the electrical signal output of the microphone 10 is coupled to an amplifier system 20 wherein the electrical signal is converted into a control signal which appears at terminal B. An oscillator circuit 50 generates an audiofrequency signal which is coupled to an amplifier circuit 60 wherein it is amplified to a level sufficient to operate output transducer 70 for subsequent application of the audio sound wave to the user's ears. The output-transducer 70 is also structured such that sounds other than the patients own voice are permitted to reach his ear so that the system does not interfere with his hearing when he is not talking. A switching circuit 40 is responsive to the control signalat terminal B for enabling operation of oscillator circuit 50 only while the patient is speaking.
In accordance with the invention, it has been found that greatly increased masking is obtained by employing a masking signal whose dominant frequency components follow the pitch variations in the patients speech. To this end, a circuit 30 is provided which is also responsive to the control signal at terminal B for effecting variations in the frequency of oscillation of oscillator circuit 50 in proportion to the changes in pitch of the patients voice. The frequency ,of the oscillator 50 may be any audiofrequency; but preferably it is made equal to the fundamental speech frequency. In addition, the output signal of the oscillator 50 is fashioned such that it is a pulsed signal wave in order to obtain substantial amounts of harmonic signal components. Thus, the output of transducer 70 is a masking sound of a fundamental frequency which follows the variation in the fundamental speech frequency resulting from changes in pitch. Moreover, by utilizing a pulsed signal wave for the masking signal, the higher harmonics of the fundamental frequency are produced and arealso varied in accordance with the variations in pitch of the patients voice. Thus, the masking sound comprises essentially the same dominant frequency components and is varied proportionally with the patients voice to achieve optimum voice masking. This is not to say, however, that the device reproduces the patients voice, which would be defeating its purpose, but rather it generates essentially the same dominant frequency components as those comprising the patients speech but in an unintelligible manner. In addition, increased efficiency of the output stage may be achieved because the pulsed signal wave may operate with a low duty cycle and still provide effective masking. Furthermore, it maintains optimum masking even as the pitch of the patients voice changes. To give a better understanding of the operation of the invention, a more detailed explanation of the circuit in the FIGURE follows below.
Referring again to the amplifying system 20, it is shown to comprise an audio amplifier 21, a pulse shaping circuit 22, a diode 23, and transistors Q and Q connected as a monostable multivibrator 24. Circuit 22 receives the amplified audio signals from audio amplifier 21 and produces a pulse train at terminal A of a frequency corresponding to the fundamental frequency of the patients voice. In this embodiment, circuit 22 produces a pulse train of a frequency equal to that of the fundamental frequency of the patients voice, although the advantageous results of the invention may still be at least partially achieved by using any desired proportional frequency relationship. Diode 23 transmits only the negative pulses appearing at terminal A to trigger multivibrator 24. Thus, the
multivibrator 24 oscillates at a rate corresponding to the fundamental frequency of the patients voice. The resulting output signal of multivibrator 24, appearing at terminal B, is a series of pulses of sufficient amplitude and width to operate circuit 30 and switching circuit 40.
In this embodiment, switching circuit 40 is in the form of a transistor 0 in series with a half-wave rectifying circuit consisting of diode 41, resistor 42, and capacitor 43. It is responsive to the signal at terminal B to turn on transistor Q and thereby enable operation of the oscillator circuit 50 by completing its energy source path from a supply potential V to ground. This controls the device so as to produce an output signal at the patients ears only while he is speaking. The time constant of resistor 42 and condenser 43 is preferably set at approximately 200 milliseconds to provide masking between normally spaced words while permitting the patient to hear environmental sounds when he is not speaking. A manual switch S is also incorporated in parallel with transistor to provide means for operating the device continuously (position 1) or automatically (position 2). Of course, the switching circuit is not limited to use with the oscillator. A similar circuit may be used in conjunction with the amplifier circuit 60 or the output transducer 70, for example, to achieve the same result.
Oscillator circuit 50 is an essentially conventional astable multivibrator 51 consisting of transistors Q and Q and associated biasing and timing circuitry. A variable resistor 52 is provided in the timing network so that the frequency of oscillation of the circuit may be adjusted to an appropriate nominal frequency in relation to the frequency range of the voice of the particular patient using the device. This pitch control may provide control of nominal frequency within the range from 75 to 250 hertz and permits persons, both male and female, having voices with different pitch characteristics to use the invention with equal benefit. The waveform of the output signal of this particular oscillator circuit is a low duty cycle (e.g., percent) rectangular wave. It therefore contains substantial amounts of the harmonic frequencies of the fundamental frequency. The invention is not, however, limited to this particular type of output signal as any signal having a relatively high harmonic content is sufficient.
Circuit 30 is a conventional RC differentiating network which responds to the essentially rectangular pulses at terminal B and develops very sharp transient pulses therefrom at terminal C. In accordance with the invention, the signal appearing at terminal C is coupled to the base of transistor Q through resistor 31. In operation, the free-running frequency of the multivibrator 51 is set to a frequency, depending on the pitch of the patients voice, lower than the patients fundamental voice frequency by pitch control 52 so that the pulse signal from terminal C overrides the voltage on the base of transistor 0 and thereby increases the frequency of operation of the multivibrator 51 to that of the fundamental voice frequency. Thus, the signal appearing at the output transducer 70 corresponds to the fundamental frequency and harmonics of the patients voice and automatically maintains this relationship even as the patients voice changes in pitch. Because the rectangular wave provides masking superior to that of prior devices using white noise masking signals, a low duty cycle may be used to thereby significantly lower the power requirements of the overall system, permitting more efficient battery use in a wearable device.
Thus the invention provides a new and improved antistuttering therapeutic device which operates more effectively and more efficiently then prior art devices. By providing a masking sound which follows the variations in pitch of the patients voice and by utilizing a signal with a relatively high harmonic content, optimum voice masking is achieved in a simple and efficient manner.
While a particular embodiment of the invention has been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects, and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of the invention.
1. In a therapeutic system for assisting a patient to overcome a tendency to stutter, of the type comprising a microphone for monitoring the speech of the patient, a sound producing device adapted to be worn by the patient, and means for delivering a masking signal to the sound-producing device to cause the latter to reduce the patients hearing response to his own voice, the improvement which comprises; means coupled to said microphone and to said masking-signal means for effecting variations in the frequency of said masking signal in accordance with variations in the pitch of the patients voice.
2. A therapeutic system as defined in claim 1, which further comprises means for maintaining the application of the masking sound for approximately 200 milliseconds after the voice of the patient ceases, thereby providing masking between normally spaced words while permitting the patient to hear environmental sounds when he is not speaking.
3. A therapeutic system for assisting a patient to overcome a tendency to stutter, of the type comprising a microphone for monitoring the speech of the patient and a sound-producing device adapted to be worn by the patient, and in which a masking signal is applied to the sound-producing device when the patient speaks to actuate the sound-producing device to at least partially override the hearing response of the patient to his own voice, the improvement which comprises; means coupled to said microphone and to said sound-producing device for developing a pulsed signal wave whose fundamental frequency component varies proportionally with variations in the pitch of the patient's voice for application as said masking signal to said sound-producing device.
4. A therapeutic device for providing voice masking to aidin the correction of a patients speech deficiency comprising:
a microphone for receiving speech sound waves and converting them into input electrical signals, said sound waves essentially comprising a fundamental frequency and harmonics thereof and being subject to frequency variations corresponding to changes in pitch of the patients voice;
signal generating means coupled to said microphone and responsive to said input electrical signals for developing a control signal;
oscillator means for generating an electrical signal having a predetermined audiofrequency of oscillation;
circuit means coupled between said signal generating means and said oscillator means and responsive to said control signal for varying said frequency of oscillation proportionally with said pitch changes;
output means coupled to said oscillator means for converting said audiofrequency electrical signal into an audio sound wave and adapted for applying said wave to the patients ear; and
switch means coupled to said signal generating means and responsive to said control signal for enabling said application of said audio sound waves.
5. A therapeutic device as defined in claim 4, in which said signal generating means comprises the series combination of a pulse shaping circuit and a monostable multivibrator coupled to said microphone and responsive to said input electrical signals for producing electrical pulses of a predetermined shape and of a predetermined frequency which varies proportionally with said variations of said fundamental frequency of said speech sound waves.
6. A therapeutic device as defined in claim 4, in which said oscillator means comprises an astable multivibrator having means for manually setting its nominal frequency of oscillation to thereby provide an audiofrequency signal containing said fundamental frequency and higher-frequency harmonic components thereof for optimum voice masking.
7. A therapeutic device as defined in claim 6, in which said circuit means comprises a differentiating network responsive to said control signal for developing transient pulses of a frequency corresponding to the fundamental frequency of said speech sound waves and applying said transient pulses to said astable multivibrator to override said frequency setting means and thereby automatically vary the frequency of the audiofrequency signal proportionally with the fundamental frequency variations of the speech sound waves.
8. A therapeutic device as defined in claim 4, in which said switch means comprises delay means for enabling said application for approximately 200 milliseconds following the cessation of said control signal, thereby providing masking between normally spaced words while permitting the patient to hear environmental sounds when he is not speaking.