US3281534A - Nasality meter - Google Patents

Description

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W. C. DERSCH v NASALITY METER oct. 2s, 1966 2 Sheets-Sheet 1 Filed May 9. 1963 Tira@ ATTORNE Y oct. 25, 1966 Filed May 9. 1963 AMPMETER MiCRO FIG.4

w. C. DERSCH NAsALI'rY METER me PERsoNs,ALL

2 Sheets-#Sheet 2 W/LL-/AM C. DERSCH FLEHR @f SWA/N ATMP/vers United States-Patenti@ i' 3,281,534 NASALITY METER Williamr C. Dei-sch', 110 Cardinal Lane,Los Gatos, Calif. Filed -May 9,' 1963, Ser. No. 279,154

16 Claims. (Cl. 179-1) This invenion pertains to speech measuring equipment and more particularly to a meter and methodvfor measuring the nasal quality ofspeech. This measure, inturn, can be significant in evaluating the treatment. of: cleft palate patients.

Briefly, by way of background, it should be understood that air expelled during speaking escapes through both the nose and mouth. When forming certain sounds, thevvelopharyngeal valve (i.e., a smallflap located tothe rear of the throat) serves to block the air passage linto the nose. Formation of certain other sounds moves the flap to open the passage permitting air to pass into the nose. Thus, in pronouncing a word such as 011, little air enters the nasal resonant chamber while nine admits considerable air to provide a distinct nasal quality. l

Where a person is formed with a cleft palate, they velopharyngeal valve is either missing entirely (as is usual) or badly deformed and inoperative. Thus, the cleftpalate patient experiences serious difficulty in controlling the nasal quality of his speech.

In an effort to impart a certain amount of control over the nasality of the patients speech, aprostheticdevice or obturator is supported at the roof oftheumouth and disposed to serve as something of a substitute for thel missing flap. Fitting a patient. with such ahdevice isf performed on a cut and try basis. The degree of successl is measured by listening to the patient speak or by emplying oral manometry or cineradiography (X-ray motion pictures), or a combination of these techniques.

One method of treatment of cleft palate patients follows a program employing graduated obturators. Other methods employ surgery. Evaluation of speech` competence by merely making a subjectivev assessment has been sufficiently crude to preclude the reaching of reliable conclusions regarding the merits of the various treatments. Devices to provide objective measurement of cleft palate performance, have included oral manometers,` the sound spectrograph, and cineradiographic equipment. Each of these measuring tools has been subject to significant limitations. What has been needed, in short, is a simple and reliable method or means for accurately measuring speech competence and particularly the nasal quality of speech.

In general, it is an object of the invention toV provide a meter for accurately measuring the nasal `quality of r speech.

Equipment for the above purpose must, of course, sort out spoken sounds from background noises and the like. A relatively recent but extremely powerful technique which detects the occurrence of certain characteristics and particularly voiced sounds is employed herein. Voiced sounds are defined in this art as those sounds which originate with air passing through the Ivocal chords and which are modulated by physical changes inthe various resonant chambers in the throat and mouth of the speaker. These sounds are distinguished from unvoiced sounds which areformed primarily by air passing through constrictive chambers in the throat, mouth or at the teeth or lips. Voiced sounds are like complex multifrequency waves, but are not truly periodic and have damped oscillatory characteristics` The voiced sounds do, however, have for fundamental as well as harmonic frequency components relatively brief but discernible intervals, and these components can usually be identifiedy The unvoiced sounds contain little or no such fundamental frequencies, which are usually of the order of a lfew hun- Patented Oct. 25, '1966 2 dred to a fewv thousand cycles per second, but are noise? like in characteriand consist of essentially random ampliftudevvibrations with time.

By way of providing furthervbackground, in the present invention; meanstarevprovidedy which sensitively disti-n'- guishY voiced from bothrunvoiced soundsand ambient noise by detectingthe occurrence of an asymmetry characteristic inelectrical signal representations of human speech. The

'asymmetry'characteristic is present only in voiced sounds, but is presentineach case therein, and results in an arn- A plitude-edifference between positive-going peaks and negative-going'rpeaksin the complex multifrequency voiced sound wave. The complexwave issplit into positive-going andcnegative-going cyclic components and the difference between them providesthe asymmetry characteristic.

t In a specific example as used herein, electrical signal representations. of human speech either prerecorded or from `a microphone input are given a phase shift to favor nasal sound frequencies and then applied-to a pair .of parallel-'coupled oppositely-poled diodes. One of the diodes passes the positive-goingsignal components in lthe complex multifrequencywave and the other diode v passes the negative-going signal components.

Each vof these com-ponentwaves isthen applied to a peak charging circuit Awhich has a time constant corresponding to a typical syllabic speech interval.

I havediscovered vth-at the ratio oftheintegrated values of. eachcomponent provides a nasality quoticnt which reliably characterizes the nasal quality vof a persons speech. Another object ofthe invention therefore is to provide a method andk means for deriving a nasality quotient which is characteristic of an individuals speech competenoe.

Accordingly, to derive the nasality quotient of an individual, I form electricall representations of speech as a .phase shifted complex wave having two'concunrently existing cyclic components. The two components are each time averaged over. a predetermined interval to provide a pair of signals respectively representing afirst and second nasality factor. Then for the period of a selected aspoken message or speech event (as defined below) I integratek each signal to derive a value for each factor and store the values derived. I then sense the value of each factorto establish the ratio therebetween. This ratio can subsequently be plotted on a graph for comparison with an established norm or otherwise utilized `as desired.

Other objects of the invention will become more readily apparent from the following detailed descriptionof a prefer-red embodiment when taken in conjunction with the drawings in'which:h

FIGURE 1 .is a block diagram representation of a nasality meter according to the invention.

FIGURE 2 is a schematic electrical circuit diagram according to the invention.

,FIGURE 3 shows a typical graph wherein the nasality quotient for each of ten individuals has been plotted.

, FIGURE 4 is a schematic electrical circuit diagram similar to FIGURE 2 with ythe application of associated `values to the various components therein.

FIGURE 5 is another` embodiment according to the .sound discrimina-ting circuit for converting electrical speech representations into a phase shifted complex wave 0 having two concurrently existing cyclic components.

Means are provided for time averaging each of the components over a predetcrmined'interval to provide a pair of signals respectively representing a first and second nasality factor. Means for integrating and storing each signal over the period of a selected spoken message or speech event is further provided in a manner to derive and store a value for each of the two nasality factors. Further, means are provided for sensing the values to provide a nasality quotient for the speech representations, as defined by the tratio between the two values.

Referring to FIGURE 1, a preferred embodiment includes means for providing electrical representations of human speech. Thus, the speech to be measured can be examined from either a microphone input 11 or via a playback transducer 12 arranged to play back :previously recorded speech events. A speech event for present purposes can be defined as a word, words, phrase or other speech-generated sound for measurement. The recitation of digits 0-9 can be a speech event, as can the pronunciation of San Francisco.

The electrical representations are fed to a nasality wave structure discrimination circuit 14 adjusted to favor nasal sounds as distinguished from other sounds. lt has been observed that changes in phase relation cause the output signal of circuit 14 to vary uniquely and identifiably with time for particular types of voiced sounds. Thus, for different phase shifts the characteristic asymmetry pattern arising during a syllable speech interval may vary, and with certain adjustments can favor positive-going cyclic components or negative-going cyclic compounds.

In the circuit of FIGURE 2 electrical input signals representative of human speech are amplified as provi-ded from a source such as microphone 11 or transducer 12. These representations are applied through a DC blocking capacitor 20 to a phase shifter 22. Here the phase shifter 22 includes a transistor 24, shown as being of PNP conductivity type, by way of example. Transistor 24 has its base 25 coupled to a minus bias through a resistor 30, and its collector 26 coupled to a -12 volt supply such as battery 32 via a resistor 33. A manually controlled main power switch 35 is disposed in the co1- lector circuit and is preferably accessible on the outside of a housing (not shown) enclosing the meter elements. The emitter 27 of transistor 24 is coupled to ground through a resistor 36.

A selected phase delay may be introduced into the monofrequency components of the amplified signals from transistor 24 by a passive circuit arranged to couple collector 26 and emitter 27. The passive circuit includes a capacitor 38 coupling collector 26 to a circuit junction point 40. An adjustable resistor 42 couples emitter 27 to the same point 40. This phase shifter 22 passes all frequencies of interest but the amount of phase shift introduced for any monofrequency component is dependent both upon the setting of the adjustable resistor 42 and the frequency itself.

As will be further explained below, varying the setting of resistor 42 serves to establish a norm or standard representative of the nasal quality of normal speaking people in a given region or locality. Thus, the nasality of persons with an impaired speech competence can be measured against a regional or localized standard of nasality.

The phase-shifted complex wave appearing at circuit junction 40 is applied through a Vpower amplifier 44 to means for forming the complex wave into two concurrently existing cyclic components.

Thus, a wave splitting circuit includes a pai-r of parallel oppositely poled semiconductor diodes 46, 47 which perform the wave splitting function. A first ofthe diodes 46 is poled to pass the positive-going cyclic components, while the second diode 47 is poled to pass negative-going cyclic components. With the reference axis of the waves being substantially at ground potential, this circuit provides accurate but separate representations of the positive and negative cyclic components of the coniplex multifrequency wave. t

Means for time averaging cach of the components over a predetermined interval to provide a pair of signals respectively, representing a first and second nasality factor is shown in FIGURE 1 as the time averaging circuit t6, 17. Thus, the nasality rfactors can be considered us the rate integrated wave components.

Circuits .16, 17 can be in the form of peak charging circuits. For example, a peak charging circuit is coupled to diode 46 and consists of a shunt capacitor 50 coupled to ground and a parallel resistor 51 likewise grounded via a circuit junction point 53. The peak charging circuit coupled to diode 47 also consists of a shunt capacitor 55 and a parallel resistor 56 both coupled to ground. Thus, resistors 51, 56 form a grounded, center tap voltage divider whereby signals appearing across resistor 51 represent a first nasality factor and signals appearing across resistor 56 represent a second nasality factor.

Diodes 46, 47 have matched characteristics as do the two peak charging circuits so that like amplitude variations result for signals developed -across resistors 51, 56 for like absolute amplitude variations derived from thc phase shifter 22. r

The discharge time constants of the peak charging circuits are alike and selected to be on the order of ms. corresponding to a typical syllabic speech interval. Signal variations occurring across resistors 51, 56 appear as relatively slow varying output signals. Signal variations for the positive-going Iand negative-going componcnts occurring across resistors 51, 56 respectively appear as relatively slow varying output signals which can each be integrated over the period of a speech event and stored. Thus with this arrangement the phase delay can be set by resistor 42 to favor nasal wave structure and thereby provide an asymmetry characteristic representative of nasality whereby the positive-going cyclic component, time averaged over the syllabic interval, will provide a nasality factor which can be integrated and stored. Similarly the negative-going cyclic component will also be time averaged to provide a second nasality factor to be integrated and stored. Means for integrating and storing each signal (representing one of the factors) for -the period of a selected speech event whereby the value of each factor for the period can be derived and stored is represented by boxes 18, 19. Thus, in FIGURE 2 a pair of summing integrator circuits are provided to integrate and store the signal components appearing across resistors 51, 56 respectively. To integrate and store the positive components, a diode 61 poled to pass positive waves and a series-coupled resistor 62 and relatively large capacitor 63 are disposed in shunt with resistance element 51. Similarly for integrating and storing native cornponents representing a second nasality factor there is provided an oppositely poled diode 64 series-coupled with resistance element 65 and capacitor 66. Similarly, diode 64, resistor 65 and capacitor 66 are disposed in shunt across resistance element 56.

During the period of time when the signal appearing at the junction between resistor 51 and diode 61 is above ground a charge is built up in the relatively large capacity condenser 63. As the signal becomes negative with respect to ground, diode 61 serves to block the draining away of the charge and accordingly for each subsequent positive-going component the charging condenser 63 is further built-up. Similarly for negativegoing components an opposite charge is built up in condenser 66.

Means for sensing the stored charge in each of storage elements 63, 66 is provided whereby the value stored in each can be selectively rend. Thus, a pair of normally open circuit branches 67, 70 are respectively coupled to the junction points between condenser 63 and resistance element 62 and between condenser 66 and -resistor 65. A meter, such as an ammeterf'68, disposed in shunt with a damping resistor 69 and connected to ground is series-connected through a scale factor resistance 71 to a manually operated switching means 74 selectively operable to connect meter '68 to terminal 72 or 73 to read the stored'charge in storage element 63 or 66 respectively.

Means are provided for resetting storage elements *'63, 66 to a relatively uncharged condition simultaneously. The storage reset means is manually operative, as by a push button. As shown in FIGURE 2 the reset means includes a pair of contact points`75, 76 connected respectively to branches 67, 70. A conductive and grounded l armature 77 is spring 'urged away `from contact `points 75, 76 by a spring 78 whereby push button 79 Acan ybe employed to simultaneously ground the vpoints 75, 76 by contacting same. Thus, in the event that a reading out of the values stored inelements 63,66 fails to drain -them of their respective charges, prior to each subsequent speech measurement, push button 79 can be utilized to virtually instantaneously withdraw the stored factors to reset the storage elements 63, 66 to a predetermined value, namely, to ground.

While the `above system has been described in sufficient detail to enable one skilled in the art to` practice the invention, a specificfexample of the complete ci-rcuit together with values, voltages and other pert-inent identifying information is disclosed in FIGURE 4. Unless noted bythe symbol omega (Q) all resistance values are in kilo-ohms. When indicated by the omega symbol the resistance values are measured in ohms. The lcapacitors are all measured'in microfarads.

Power amplifier 44 can be of conventional construction providing a gain on the order of twenty decibels and adjustable to compensate for the microphone selected. Meter 68 can be of conventional construction such as an ammeter having a range between plus and minus 50 microamperes.

In operation, assuming the switch 35 is closed, a person can be asked to recite into microphone 11 the digits oh to nine thereby acumulating the storing of the respective values of a first and second nasality factor in condensors 63, 66. These values are then selectively read by moving switch 74 to terminal 73 and then to terminal 72. Dividing the first-read value by the second-read value provides a nasality quotient. For example, as shown in FIGURE 3, D. J. has a nasality quotient of approximately 1.3. The nasality quotient for five normal persons is shown plotted against unity as a base reference. Of the ve normal persons, note that F. S. had a head cold thereby generating a nasality quotient showing more nasality than the others. Five persons having a cleft palate problem, thereby being precluded from closing the air passage to the nose, showed more nasality with the exception of S who was fitted with a prosthetic device, or obturator, for correcting the cleft pala-te speech deficiency. Thus, a program of progressive obturators can be evaluated by periodically making truly objective meas-` urements of the nasality of the persons speech.

According to another embodiment of the invention as shown in FIGURE 5, nasality in speech can be continuously monitored by direct coupling meter 68 to branches representations into a phase-shifted complex wave having two vconcurrently existing cyclic components, means for time averaging each of thecompo'nents over a predetermined interval lto provide agpair of signals respectively representing a first `and vsecond nasality factor, means `for'integratingand'storing each said signal during speech over the period of a selected speech event to A'derive a "stored value foreach said factor, and 'means for sensing said stored values toprovide a nasality`qu'ot`ient, for the representations, defined bythe ratio `betiveen said values.

3. A meter as defined in claim 2 wherein the lastrnamed means includes switching means lfor selectively sensing said values.

4. A meter for measuring 'the nasal quality kof 'electrical representations of speech comprising a voiced sound 'discriminating circuit for converting electrical speech representations vinto a phase lshifted complex wave `having two concurrently existing cyclic components of opposite polarity sense, means for time averaging each of the j components lover 'a predetermined interval to provide a 67, at a junction point 81. Thus, while a person speaks continuously'into microphone 11, phase shift control (resistor 42) is varied to null the meter 68 at its midpoint. The degree of displacement of the wiper for resistor 42, properly calibrated, then provides a direct reading representing the -individuals nasality quotient.

I claim: f

1. A method of measuring the nasal quality of speech comprising the steps of forming electrical representations of voiced sounds as a phase shifted complex wave having two concurrently existing cyclic components', time averaging each of the components over a predetermined interval to provide a pair of signals respectively reprepair of signals of opposite polarity respectively representing a first and second nasality factor, means serving to integrate and store each said signal over the period of a selected speech eventto derive a stored value for e-ach said factor, and means for sensing said values to provide a nasality quotient, for the representations, as'defined bythe ratio between said values. l

5. A meter as defined in claim 4,*further including switching means for selectively sensing each of said values.

, '6. A meter as defined in claim 4, furtherincl'uding means for resetting said storage means to remove said stored values.

7. The method of measuring the nasal quality of speech comprising the steps of forming electrical representations of speech as a complex wave, shifting the phase of said complex wave, splitting saidphase-shifted complex wave into two concurrently existing cyclic components, time averaging each of the components over a predetermined interval to provide a pair of signals respectively representing a first and second nasality factor, integrating and storing each said signal over the period of a selected speech event to derive a stored value for each saidfactor, sensing the value of each factor to provide a ratio therebetween defining a nasality quotient, and withdrawing the stored factors from storage to reset same prior to receiving a factor for a subsequent speech event.

8. A nasality meter for measuring' and indicating the nasal quality of speech comprising means serving to provide a complex multifrequency signal representative of speech, means serving to shift the phase of said complex signal to emphasize a predetermined nasal Wave structure, means responsive to the phase shifted complex signal serving to divide the signal into two concurrently existing cyclic components, means for time averaging each of the components over a predetermined interval to constitute said components a first and second nasality factor, means serving tonintegrate each said factoral component during a selected speech event to derive the value thereof and to separately store said values, and means for indica-ting the storedvalue of said each component to provide a nasality quotient defined by the ratio between said values.

9. A nasality meter as defined in claim 8 wherein the last-named means further includes means selectively operable to visually indicate the stored value of each said component independently.

10. A nasality meter as defined in claim 8 wherein the penultimate named means includes means for selectively resetting same to a predetermined value.

1l. A nasality meter as defined in claim 8 wherein th last-named means includes electrical measuring means and manually operable switching means serving to selectively couple said measuring means to read out either of said stored values independently whereby the ratio of said values can provide a nasality quotient for said speech event.

12. A nasality meter as defined in claim 11 further including manually operable means for resetting said storage means to a predetermined value.

13. A meter for measuring the nasal quality of electrical representations of speech comprising means for shifting the phase of complex speech waves among said electrical representations to provide a unique asymmetry characteristic thereof, means for splitting the phase-shifted complex wave into two concurrently existing cyclic components, means for time averaging each of the components over a predetermined syllabic interval to provide a pair of signals respectively representing a first and second nasality factor, integrating and storage means including a pair of oppositely poled unilateral conducting elements each series-coupled to an associated resistancecapacitive summing circuit, said unilateral elements being respectively coupled to pass only one or the other of said components to separately derive and store the respective values of the components for the period of said speech event, and means serving to selectively read out and visually indicate each of said stored values, the lastnamed means including a meter having a visual scale and manually operable switching means for selectivelyreading out the stored value of either of said summing circuits.

14. A meter as defined in claim 13 further including means for resetting said summing circuits including manually operable means for simultaneously equalizing the charge on said respective capacitive elements.

15. A meter for measuring the nasal quality of electrical representations of speech comprising a voiced sound discriminating circuit for converting electrical speech representations into a phase-shifted complex wave having two concurrently existing cyclic components, means for time averaging each of the components over a predetermined interval to provide a pair of signals respectively representing a first and second nasality factor, means for integrating each said signal during speech yto derive a value for each said factor, and means for sensing said values to provide a nasality quotient, for the representations, dened by the ratio between said values.

16. A meter for continuously monitoring the nasal quality of speech representations comprised as defined in claim 15 and further including means for varying the degree of phase shift applied to said complex wave and connected to vary one of said components with respect to the other to equalize same, whereby the degree of variation required to equalize said components provides a measure of the nasality quotient of the speech.

No references cited.

KATHLEEN H. CLAFFY, Primary Examiner.

R. MURRAY, Assistant Examiner.

Claims (1)

1. A METHOD OF MEASURING THE NASAL QUALITY OF SPEECH COMPRISING THE STEPS OF FORMING ELECTRICAL REPRESENTATIONS OF VOICED SOUNDS AS A PHASE SHIFTED COMPLEX WAVE HAVING TWO CONCURRENTLY EXISTING CYCLIC COMPONENTS, TIME AVERAGING EACH OF THE COMPONENTS OVER A PREDETERMINED INTERVAL TO PROVIDE A PAIR OF SIGNALS RESPECTIVELY REPRESENTING A FIRST AND SECOND NASALITY FACTOR, INTEGRATING EACH SAID SIGNAL OVER THE PERIOD OF A SELECTED SPEECH EVENT

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