A. Maynard Engebretson

Study of variations in the male and female glottal wave

A reflectionless metal tube which can act as a pseudoinfinite termination of the vocal tract was used to collect glottal volume-velocity waveforms produced by 10 male and female adult subjects. From each subject glottal volume-velocity samples were collected of normal, loud, and soft voice; falsetto and creaky voice; monosyllables with rising and failing intonation; and three-syllable utterances containing primary lexical stress on one of the three syllables. Analysis of the data indicates a wide variation of the glottal waveform shape, its rms intensity and fundamental frequency, phase spectrum, and intensity spectrum. It is observed that as the fundamental frequency changes over time, the glottal source varies in one of two different ways. In one type of change, the harmonic relations in the glottal spectrum become steeper as fundamental frequency rises. In a different type of glottal-wave change, relations between harmonics tend to remain the same despite a change in the fundamental frequency; the source spectrum in this case is simply shifted along the frequency and amplitude axes as a function of fundamental frequency. To account for these variations in the glottal source, at least three factors must be known: the sex of the speaker, the voice register in which he phonates, and the linguistic context in which the phonation occurs.

Electronic filters, hearing aids and methods

An electronic filter for an electroacoustic system. The system has a microphone for generating an electrical output from external sounds and an electrically driven transducer for emitting sound. Some of the sound emitted by the transducer returns to the microphone means to add a feedback contribution to its electical output. The electronic filter includes a first circuit for electronic processing of the electrical output of the microphone to produce a filtered signal. An adaptive filter, interconnected with the first circuit, performs electronic processing of the filtered signal to produce an adaptive output to the first circuit to substantially offset the feedback contribution in the electrical output of the microphone, and the adaptive filter includes means for adapting only in response to polarities of signals supplied to and from the first circuit. Other electronic filters for hearing aids, public address systems and other electroacoustic systems, as well as such systems, and methods of operating them are also disclosed.

Model for the Nonlinear Characteristics of Cochlear Potentials

In an effort to clarify certain ideas about the nonlinear behavior of the cochlea, simple nonlinear network was studied. The network was constructed to produce peak‐clipping distortion similar to that seen in the cochlear microphonic (CM) of the basal turn of the cochlea. The interference between pairs of tones and the growth of combination tones as well as other manifestations of nonlinearity were similar for the ear and for the network. The degree of similarity between the output of the network and CM from the ear is shown by instantaneous waveforms and by input‐output functions. An important finding of this paper is that the linearization effect of two‐tone interference in the ear is a property of nonlinear systems, which occurs in the network also. The results also support recent theories that summating potential (SP) is produced by asymmetric nonlinearities in the ear.

Implantable middle ear hearing aid system and acoustic coupler therefor

The acoustical coupler has a closed-bottom containment with compliant diaphragm attached to the containment periphery to form an acoustic chamber. A length of tubing is connected through the side or bottom of the containment to the chamber for conveying sound pressure between the chamber and an electroacoustic transducer connected at the other end of the tubing. The transducer may be either a microphone or a hearing aid receiver. The electroacoustic transducer, being too large for direct placement within the middle ear cavity may be located elsewhere in the skull, such as behind the ear adjacent to the surface of the skin. When connected to a microphone the coupler may be placed within the middle ear cavity behind the tympanic membrane and may be attached to the malleus with a wire hook secured to the coupler diaphragm. When attached to a receiver or vibration sending unit the coupler may be attached to the incus end of the stapes using a porous disc secured to the coupler diaphragm, the porosity of the disc permitting tissue growth and infusion whereby the stapes becomes permanently attached to the disc. The acoustic couplers may be used with a wide range of electronic signal processing and amplification circuitry tailored to the particular patients hearing loss.

Implantable hearing aid coupler device

The acoustical coupler has a closed-bottom containment with compliant diaphragm attached to the containment periphery to form an acoustic chamber. A length of tubing is connected through the side or bottom or the containment of the chamber for conveying sound pressure between the chamber and an electroacoustic transducer connected at the other end of the tubing. The transducer may be either a microphone or a hearing aid receiver. The electroacoustic transducer, being too large for direct placement within the middle ear cavity may be located elsewhere in the skull, such as behind the ear adjacent to the surface of the skin. When connected to a microphone, the coupler may be placed within the middle ear cavity behind the tympanic membrane and may be attached to the malleus with a wire hook secured to the coupler diaphragm. When attached to a vibration sending unit the coupler may transfer the generated vibration directly to the incus end of the stapes. In one embodiment, this transfer is effected by means of a hollow tube having a generally hollow member therein and containing a quantity of low loss material. The member defines one end connected to the vibration sending unit and a second end connected directly to the stapes.

Method of readout of implanted hearing aid device and apparatus therefor

The implanted device includes a rectifier circuit which is switched between modes of half wave and full wave rectification in response to the signal to be conveyed. The external device is inductively coupled to the implanted device through a pair of coils, one coil being embedded beneath the skin, forming the primary and secondary windings of a transformer. The external device delivers energy to the implanted device in amounts which vary in accordance with the rectification mode of the implanted device. By monitoring the energy delivered, the external device determines the rectification modes as they are switched and thereby ascertains the signal being conveyed from the implanted device.

Indirect assessment of the contribution of subglottal air pressure and vocal-fold tension to changes of fundamental frequency in English.

The contributions of vocal-fold tension and of subglottal air pressure to changing fundamental frequency F0 are indirectly assessed by comparing human glottal-source data with synthetic glottal waveforms generated by the Ishizaka-Flanagan two-mass model of vocal-fold vibration. In this model, synthetic male and female glottal waves may be generated with known values of subglottal air pressure and vocal-fold tension. Human glottal waves were recorded with a reflectionless tube into which ten male and female adults phonated. The subjects produced interrogative (rising F0) and declarative (falling F0) glides and trisyllabic words with primary stress on the initial, medial, or final syllable. Two types of change in the glottal wave over time are possible, depending on whether F0 is changed primarily by vocal-fold tension or by subglottal air pressure. Comparison of the natural and synthetic glottal waves indicates that (1) the rise of frequency in interrogative words is due principally to increasing vocal-fold tension, while (2) the fall of frequency in declarative words is due principally to decreasing subglottal air pressure; (3) in the polysyllabic words, the change of frequency within syllables resembles that of the declarative monosyllables and appears due primarily to changes of subglottal air pressure; and (4) the heightened f0 of the stressed syllable is due to an increase in the vocal-fold tension, typically accompanied by increased subglottal air pressure.

Vowel normalization: Differences between vowels spoken by children, women, and men

Using the data of Peterson and Barney [J. Acoust. Soc. Am. 24, 175–184, (1952)] we have sought transformations of the frequency scale (e.g., Mels) and rules of combination of values of the fundamental (F0) and the formants (F1, F2, and F3) (e.g., F2/F1, F3/F2) that will eliminate differences between talker groups (children, women, and men) while maintaining differences between vowel categories. The ratios of the between‐ to the within‐vowel category variation as well as the minimum separations between vowel categories, scaled by the within‐category variation, were calculated. Of the many frequency transformations and combination rules examined, the vector [log (F1/F), log (F2/F), log (F3/F)], where F = (F1⋅F2⋅F3)1/3, provides the best clustering of the vowels and nearly eliminates differences between talker groups. This suggests that vowels are characterized by their spectral shapes when plotted on log axes. Thus the usual range of differences between children, women, and men in the absolute location ...

Preliminary research with a three‐channel vibrotactile speech‐reception aid for the deaf

Envelopes of signals from (1) an accelerometer attached to the talkers nose, (2) a microphone near his mouth, and (3) an accelerometer attached to his throat (see Nickerson and Stevens) were multiplied by a 100‐Hz square wave and the products were used to drive three vibrators. Normally hearing subjects with simulated total loss of hearing for speech felt signals on vibrator 1 proportional to the amplitude of vibration in the talkers nose, on vibrator 2 proportional to the amplitude of sound near the talkers mouth, and on vibrator 3 proportional to the amplitude of vibration in the talkers larynx. The vibrators were on separate fingers of the same hand or on a single finger. When the three‐channel aid is used with lipreading, scores on syllable and word tests are better (sometimes dramatically) than with lipreading alone. Improvement is demonstrated for nasal/oral, voiced/voiceless, and continuant/interrupted discriminations. Variations in vowel duration as with voiced and voiceless final consonants a...

A computer program for fitting a master hearing aid to the residual hearing characteristics of individual patients

The electroacoustic characteristics of an experimental master hearing aid are determined by the choice of transducers and settings of 26 controls which include a preamplifier, the gains and limiting levels in each of 12 channels as well as the gain of a final power amplifier. Here, a computer program which aids in the fitting of the electroacoustic characteristics of this aid to the characteristics of a patients residual hearing is described. The patients audiologic data and the hearing-aid parameters are entered into the computer and the gain and limiting level of each channel of the hearing aid are adjusted until an appropriate fit is achieved. The results of the fitting procedure are displayed on a graphics terminal. Permanent copies of the results can be produced on a printer-plotter. Included in the results for each of 12 channels are (1) the discomfort level, most comfortable listening level, and hearing threshold of the patient, and (2) the maximum output and noise floor of the hearing aid as well as the aided speech level. This approach has simplified the problem of fitting a complicated hearing aid to a patients residual hearing and seems to offer attractive possibilities for fitting commercial hearing aids in the future.