C. Berger-Vachon

Evoked Otoacoustic Emissions: Relative Importance of age, Sex and Sensorineural Hearing-Loss Using a Mathematical Model of the Audiogram

The influence of age, sex and of hearing loss on the EOAEs were studied in 140 subjects. The EOAEs were never found when hearing loss on the best hearing frequency was above 40 dB HL and when the threshold of intelligibility was above 45 dB HL. The presence of EOAEs therefore does not only give specific information on the midfrequencies, but also shows a hearing loss below or equal to 40 dB HL on at least one frequency. In addition, there is a relation between the audiometric curve and the spectrum analysis of EOAEs. These seem to be promising results for clinical applications.

Auditory Brainstem Response (ABR) Latency: Relative Importance of Age, Sex and Sensorineural Hearing-Loss Using a Mathematical Model of the Audiogram

Influences of age, sex and audiogram on ABR latencies have been studied. Using a mathematical model of audiogram, the analysis of data finds a relative importance of age, sex and audiogram similar to previous studies. Audiogram slope was correlated only with the latencies of waves I and V, and multiple regression analyses indicate the slope effect is relatively weak compared to that of the other parameters. Using a mathematical model of audiogram did not improve the ABR variance across subjects, underscoring the need to discover other relevant variables to explain ABR latency.

Automatic analysis of auditory nerve electrically evoked compound action potential with an artificial neural network

The auditory nerves electrically evoked compound action potential is recorded in deaf patients equipped with the Nucleus 24 cochlear implant using a reverse telemetry system (NRT). Since the threshold of the NRT response (NRT-T) is thought to reflect the psychophysics needed for programming cochlear implants, efforts have been made by specialized management teams to develop its use. This study aimed at developing a valid tool, based on artificial neural networks (ANN) technology, for automatic estimation of NRT-T. The ANN used was a single layer perceptron, trained with 120 NRT traces. Learning traces differed from data used for the validation. A total of 550 NRT traces from 11 cochlear implant subjects were analyzed separately by the system and by a group of physicians with expertise in NRT analysis. Both worked to determine 37 NRT-T values, using the response amplitude growth function (AGF) (linear regression of response amplitudes obtained at decreasing stimulus intensity levels). The validity of the system was assessed by comparing the NRT-T values automatically determined by the system with those determined by the physicians. A strong correlation was found between automatic and physician-obtained NRT-T values (Pearson r correlation coefficient >0.9). ANOVA statistics confirmed that automatic NRT-Ts did not differ from physician-obtained values (F = 0.08999, P = 0.03). Moreover, the average error between NRT-Ts predicted by the system and NRT-Ts measured by the physicians (3.6 stimulation units) did not differ significantly from the average error between NRT-Ts measured by each of the three physicians (4.2 stimulation units). In conclusion, the automatic system developed in this study was found to be as efficient as human experts for fitting the amplitude growth function and estimating NRT-T, with the advantage of considerable time-saving.

2f1-f2 Distortion Product Otoacoustic Emission Latency: Changes with Frequency and Level of Primaries

Distortion product otoacoustic emissions (DPOAEs) provide a non-invasive and relatively direct method for evaluating cochlear travel time in humans. In the present study, the 2f1-f2 DPOAE latency was deduced from DPOAE phase shift according to f2 frequency shift, with f1 being fixed, using the ILO92 system. Latencies of 2f1-f2 DPOAEs were recorded at various primary frequencies and levels. Results were not wholly consistent with previous latency estimates. This study showed that the functions describing both 2f1-f2 DPOAE latency decrease with primary frequency increase, at several primary-tone levels, and 2f1-f2 DPOAE latency decrease with primary-level increase, at various frequencies, are best fit by exponential equations. The results of the evaluation of the latency-frequency-level relationship indicated the possibility of linking these three variables by the following expression: Latency = 68.30 exp (-0.027I -0.000434 f)+1.13.

Acoustic Discrimination of Velar Impairment in Children

Cepstral coefficients calculated out of a linear prediction have been used to discriminate two groups of 19 control children and 12 patients with velar impairment. French vowels /a/, /i/, /u/ had been studied using the cepstral coefficients. Vowels /i/ and /u/ appeared to be efficient to perform the separation on acoustic grounds. A 100% recognition score can be reached when the two vowels are considered together. Modifications of the cepstrums dealing with velar incompetence are also discussed. A way to make an automatic grading of the pathology is finally presented.

Acoustical recognition of laryngeal pathology using the fundamental frequency and the first three formants of vowels.

The recognition of laryngeal pathology by analysis of the voice is investigated. The fundamental frequency and the first three formants are considered. The recognition strategy is based on comparison with normal ranges calculated over 200 ordinary voices, grouped in ten age classes ranging from 20 to 70 years, for males and females. 220 test voices are studied divided into four groups: normal voices, functional dysphonia, nodules and recurrent nerve palsy. Each subject is marked according to his/her normal range. Parameters (or items) are calculated on the Interactive Laboratory System workstation. The vocalic material is composed of 11 vowels taken from a sentence. Results are given in terms of the number of values out of the normal ranges. Statistical analysis considers both parameter ability and error rates in pathology recognition. Pathology recognition shows the following error percentages: 23% for dysphonia, 14% for nodules and 33% for recurrent nerve palsy. Parameters do not show the same efficiency for voice pathology characterisation. Formants appear to be better than the fundamental frequency.

Acoustical recognition of laryngeal pathology : a comparison of two strategies based on sets of features

The efficiency of sets of acoustical features discriminating pathological voices from control voices is reported. Two strategies were compared. The first (called the ‘distance strategy’) was built upon a statistical distance of voice features to reference values obtained for a set of healthy (reference) voices. The second strategy (called the ‘range strategy’) is based on the position inside or outside normal ranges established from a reference population; results based on this strategy were presented in a previous paper. Reference values were calculated from a database of 200 healthy voices distributed into 10-year age groups ranging from 20 to 70. Comparisons were made using a second database of 220 voices, including 65 control, 51 functional dysphonia, 50 with nodules on the vocal folds and 54 recurrent nerve palsy. The phonetic material was compared of 17 French vowels: 11 vowels in a sentence, three isolated vowels and three segments (beginning, middle and end) of the sustained vowel/a/. Four acoustical features were considered for each vowel: the voice fundamental (f0) and the first three formant frequencies. Acoustical features were calculated on an ILS (Interactive Laboratory System) analysis system (workstation). The separation of each pathological group from the control group, using sets of acoustical features, was statistically assessed. From the strategy point of view, results indicated that (i) the fundamental frequency f0 was the best measure to separate normal from pathological voices with the distance strategy; (ii) when the formants were taken, the range strategy performed better in separating the voices. For classification of pathologies, the best separation coefficients were obtained with nodules and the worst with recurrent nerve palsy. Overall, it was seen that the separation between control and pathological voices was most efficient when measured using the distance strategy for f0. The range strategy was useful with formant frequencies.

A computer system for the lablling of phonatory pathologies in child

A computer system has been developed to make a labelling of phonatory pathologies. Several methods and parameters were tested to take into account some modifications observed in pathologies. First studies on velar impairment and kissing nodules yielded promishing results.