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Biomedical subjects

C H Chouard

Publications and source records attributed to C H Chouard.

At least 19 recordsLinked to original sources
PubMed2001

[Urban noise pollution].

Noise is responsible for cochlear and general damages. Hearing loss and tinnitus greatly depend on sound intensity and duration. Short-duration sound of sufficient intensity (gunshot or explosion) will not be described because they are not currently encountered in our normal urban environment. Sound levels of less than 75 d (A) are unlikely to cause permanent hearing loss, while sound levels of about 85 d (A) with exposures of 8 h per day will produce permanent hearing loss after many years. Popular and largely amplified music is today one of the most dangerous causes of noise induced hearing loss. The intensity of noises (airport, highway) responsible for stress and general consequences (cardiovascular) is generally lower. Individual noise sensibility depends on several factors. Strategies to prevent damage from sound exposure should include the use of individual hearing protection devices, education programs beginning with school-age children, consumer guidance, increased product noise labelling, and hearing conservation programs for occupational settings.

Animals↗
PubMed2001

A fractal approach to the features of speech consonants.

Fractal dimension (D) quantifies the roughness of a temporal signal and estimates its degree of freedom, allowing a good approach for its fluctuations. This present study of consonants follows the D-assessment of vowels which was presented at the Copenhagen Collegium Meeting. Using a 16 kHz time sampling the D-values of consonants were studied in the consonant-vowel context of the French language. Each consonant was pronounced four times by six males and six females. For D-measurement of long consonants the same method was used, i.e. the dyadic box-counting method and its 10 points of D-measurement (10pD) as that used for vowels. In the aim to approach infinitely small time scales, and to appreciate at least the tendency of the 10-point set, i.e. the D value to which tends this set, the slope of the three last points (3pD) was also calculated. For the plosion part of plosive consonants, a semi-continuous box-counting method devoted to the D-measurement of a short, single-dimension temporal signal was designed. This study consistently demonstrates that (i) there is a significant difference between males and females, as far as voiced and non-plosive consonants are concerned; (ii) plosive consonants are not fractal; (iii) among long consonants, D-value of fricatives are significantly different (p < 0.01), as far as 3pD measurement is considered; and (iv) in the case of nasal consonants [m] and [n], this categorization is efficient for both 3pD and 10pD measurements (p < 0.05). There results will be commented on and discussed with the aim of clinical use.

Adult↗
PubMed2001

[Fractal dimension of speech].

Fractal dimension (D) quantifies the roughness of a temporal signal and estimates its degree of freedom, allowing a good approach of its fluctuations and roughness. Using a 16 kHz time sampling and the box-counting method, we studied Ds of some of the main French phonemes, i.e. [a], [e], [i], [o], [y], and consonants in a consonant-vowel context pronounced 4 times by 10 males and 10 females. For D measurement of long phonemes we used the dyadic Box Counting method and its 10 points D measurement (10pD). For plosion part of plosives consonants, we designed a Semi Continuous Box Counting method devoted to D measurement of short single dimension temporal signal. In the aim to approach infinitely small time scales, and to appreciate at least the tendency of these 10 points set, we calculated also the slope of the 3 last points (3pD). Our study consistently demonstrates that vowels are not fractal; plosive consonants are not fractal; long fricative consonants are fractal; males Ds are significantly higher females Ds, as far as only vowels and long voiced consonants are concerned; there is a significant difference (p < 0.01) between 3pD values of vowels (couple [a] [y] excepted), and fricative consonants (couple [[symbol: see text]]] [f] excepted). In case of nasal consonants, this categorisation is efficient using both 3pD and 10pD measurements (p < 0.05). These results will be commented and discussed, in the aim of clinical use, i.e. dysphonia follow up and auditory prosthesis speech signal processing.

Female↗
PubMed2000

A fractal approach to normal and pathological voices.

Using the box-counting method, we demonstrated recently that the stationary signal of vowels is not fractal, but provides the opportunity to design in the smallest scale a kind of signature for each vowel. This fractal approach to these components of speech allows us to quantify the roughness of the voice, between I (sinusoidal complex signal) and 2 (white noise). We used this method to compare these values in normal and pathological voices. We studied the speech of 10 normal speakers, 6 patients suffering from unilateral vocal fold palsy and 6 suffering from various other dysphonias. The meaning of this fractal measurement is discussed and compared with electroglottogram and spectrographic analysis.

Adult↗
PubMed2000

[Q.A.L.Y. index and assessment of cost efficiency of the cochlear implant in acquired profound deafness].

Cost utility analysis is a method of cost-effectiveness analysis which provides results in terms of cost per quality-adjusted life-year (Q.A.L.Y.). This method is progressively largely used for medical technology assessment. It permits cost-effectiveness comparisons between medical interventions. The cost per Q.A.L.Y. of cochlear implant was determined in 30 adult patients suffering from acquired profound deafness. This study indicates that this technology provides significant improvements and is quite cost-effective. However, as far as profound deafness is concerned, the reliability of Q.A.L.Y. needs to be improved.

Adult↗
PubMed1999

A study of speech fractal dimensions.

The fractal dimension (D) of a signal gives an estimate of its degree of freedom, which allows estimation of its fluctuations. Using 16 kHz time sampling and the box counting method we studied the Ds of some of the main stationary parts of French speech, the phonemes [a], [e], [i], [o], [y], pronounced 4 times by 10 males and 10 females. Our study demonstrated that the stationary signal of vowels is not fractal, but may, at the smallest scale, provide a kind of signature for each vowel, though the present categorization is not totally significant. Since the box counting method objectifies and quantifies the roughness of the signal, this procedure may be useful for clinical applications. In case of dysphonia, moreover, these signatures could be perhaps be included in the speech signal processing of cochlear implants.

Female↗
PubMed1999

CT and MR findings of Michel anomaly: inner ear aplasia.

In 1863, Michel described a condition characterized by a total absence of differentiated inner ear structures associated with other skull base anomalies, including an abnormal course of the facial nerve and jugular veins. Michel aplasia clearly differs from Michel dysplasia, in which arrest of embryologic development occurs later. Recently, the role of otic capsule formation on mesenchymal differentiation was reported as well as the impact of the genetic deletion of the homeobox gene on the development of the ear, cranial nerves, and hindbrain. We report two patients with a total absence of inner ear structures bilaterally, illustrating the characteristic appearance of Michel aplasia and associated skull base anomalies.

Adolescent↗
PubMed1998

[The cochlear implant. Study in the profoundly deaf adult from the standpoint of quality of life and therapeutic cost (QALY Index of Quality)].

Cost utility analysis is a method of cost-effectiveness analysis which provides results in terms of cost per quality-adjusted life-year (QALY). This method is progressively largely used for medical technology assessment. It permits cost-effectiveness comparisons between medical interventions. The cost per QALY of cochlear implant was determined in 30 adult patients suffering from acquired profound deafness. This study indicates that this technology provides significant improvements and is quite cost-effective. However, as far as profound deafness is concerned, the reliability of QALY needs to be improved.

Adult↗
PubMed1998

[A report of two familial cases of Michel syndrome (bilateral agenesis of the inner ear)].

In two siblings, wearing conventional hearing aid, presenting profound but not total congenital deafness, with no particular antecedents, the imaging destined to confirm the indication of a cochlear implant revealed a total bilateral agenesis of the inner ear. In one of the children, this imaging was confirmed by an exploration of the middle ear performed during a tonsillectomy that was otherwise necessary. We will summarize the literature concerning Michel's Disease, exceptional in its princeps form, and we will discuss the manner of action of conventional devices in these cases which are a priori without any sensorial element.

Adolescent↗
PubMed1998

[Digital multi-filter auditory prosthesis: study of its efficiency in function of number of filters and their programming].

We designed a prototype of a 7-filter digital auditory prosthesis table prototype. For each of these filters frequency band width, amplification and compression were programmable in order to adapt these parameters to the deaf patient's audiometric particularities. We compared the hearing improvement it was possible to obtain either with the 3-analogue-filter auditory prosthesis Triton 3004 from Siemens, or with our prototype as a function of the number of filters (3, 4 or 7) and their frequency band width programmability. We tested 21 patients suffering from middle or severe neurosensory hearing loss. This study allows to demonstrate that to overpass the present analogue T004 device a 7 programmable-width-filter strategy seems to be the most appropriate. Further studies benefiting with material improvement of our prototype and finer audiometric adjustment of filter strategies as well as long term clinical studies have to be carried out.

Acoustic Stimulation↗
PubMed1998

[Cochlear implant and cerebral dominance].

On right handed people the right ear is considered to transmit speech information, and the left ear musical and cognitive information. These dominating ear properties are not exactly symmetrical in the left handed population, and are more consistent in females than in males. CI efficacy assessment is strongly based on speech intelligibility performances, because these criteria allow to measure the social reinsertion and communication possibilities. Consequently, one may ask if the relationship of the implanted side and the patient's handness could not be an important factor of this CI efficacy. We studied this relationship on 71 post-lingually deaf adult implantees. We measured patients handness using the Schachter's version of the so called Edimburg questionnaire described by Geschwind; this measurement has been moderated to take count of ambidextrous and mixed-handed population. Post operative performances has been assessed using the Francophone Protocol devoted to adults. We found that there is no significant correlation between these post-operative performances and the studied relationship. We estimate: 1) This absence of correlation is probably due to the high number of data which lead to determine the ear for implanting. 2) As far as this choice is feasible, dominating ear must nevertheless be elected, not only for theoretical reasons, but because the dominating hand may be easily employed for antenna adjustment. 3) As handness is strongly evident only after 4 y.o., and as left-handness seems to be more frequent on a congenitally deaf population, this choice is more problematic on less than 2 y.o. deaf children.

Cochlear Implantation↗
PubMed1998

[Cochlear implant in the aged patient].

Despite the fact that elderly people live frequently alone and frequently have difficulties of vision, is it reasonable to refuse to supply a patient with a cochlear implant only because he is too old? We compare the results of 87 post-lingually implantees as a function of age, less than 60 years (young) and 60 years or more (old). We assessed the implant efficacy using the Protocole Francophone d'Evaluation (PFE), appreciated the speech-therapist's opinion and the patient's satisfaction, and counted the number of hours per day the implant was used (H/D). The PFE score was significantly higher in young than old. However the speech-therapist's opinion and the patient's satisfaction as well as H/D did not differ significantly in the 2 series. Elderly people are supplied with a great benefit from cochlear implants. Therefore age is not a contraindication for implantation.

Adult↗
PubMed1998

[Indications for the cochlear implant in partial deafness of the adult].

The last (may 1995) NHI Consensus Development Conference on cochlear implant recommends to extend the use of cochlear implant for adult patient suffering from bilateral acquired severe hearing impairment. Its indications are a severe-to-profound sensorineural hearing loss bilaterally presenting an open-set sentence recognition scores less than or equal to 30 percent under best aided conditions. We report the results of our 4 first implantees responding to these criteria, and discuss the mechanisms of the speech intelligibility improvement which has been obtained.

Audiometry, Pure-Tone↗
PubMed1997

Asynchronous interleaved stimulation (AIS): a new speech coding strategy for cochlear implant.

Cochlear implants use a fixed or F0 dependent stimulation rate, whatever the sound analysed (vowel or consonant) or procedure (fixed filters or FFT). We present a procedure which varies as a function of the input signal. This method is based on FFT analysis using a variable width analysis window. Short windows are applied on the transient part of the signal, providing poor frequency resolution but good time resolution; they permit us to accurately follow the speech signal in time during its fast temporal variations. Large windows are applied on the stationary parts of the signal, providing better frequency resolution but poor time resolution. Transient parts of the speech order this window switching; they are detected using the statistical properties of the FFT; moreover, the narrow windowing is coupled to an increase of the stimulation frequency. This strategy has been implemented using the DIGISONIC cochlear implant software, and clinically assessed in 6 regular cochlear implant users, on the basis of a consonant-vowel-consonant test. This Asynchronous-Interleaved-Stimulation (AIS) strategy provides the patients with better discrimination than fixed window FFT analysis. The coding protocol will be described and results presented.

Cochlear Implants↗
PubMed1997

[Hearing impairment fitting: study of an auditory prosthesis with 7 entirely programmable filters].

We designed a 7-filter digital auditory prosthesis table prototype. For each of these filters frequency band width, amplification and compression were programmable in order to adapt these parameters to the deaf patient's audiometric particularities. We compared the hearing improvement it was possible to obtain with our prototype as a function of the number of filters (3, 4 or 7) and their frequency band width programmability. We tested 21 patients suffering from middle or severe neurosensory hearing loss. This study allows to demonstrate that a 7 programmable-width-filter strategy seems to be the most appropriate.

Cochlear Implants↗