The Vibrant Soundbridge® middle ear implant: A historical overview.

OBJECTIVE: To present a historical overview of the Vibrant Soundbridge® (VSB) middle ear implant (MEI), since its beginning in the 1990s to date and to describe its course and contemplate what it might become in the future. HISTORY: MEIs started to take form in researchers' mind in the 1930s with the first experiment of Wilska. In the 1970s, several devices, such as the Goode and Perkins', the Maniglia's, or the Hough and Dormer's were created but remained prototypes. It is only in the 1990s the devices that emerged remained on the market. In 1994, Symphonix, Inc. was created and aimed to manufacture and commercialize its semi-implantable MEI, the VSB. The principle of the VSB lies on a direct drive of the sound to a vibratory structure of the middle ear through an electromagnetic transducer, the floating mass transducer (FMT). The particularity of the system VSB is the simplicity of the transducer which is made of both the magnet and the coil; thus, the FMT, fixed on a vibrating middle ear structure, mimics the natural movement of the ossicular chain by moving in the same direction. The goal of the VSB was to give an alternative to patients with mild-to-severe sensorineural hearing loss who could not wear hearing aids (HAs) or who were unsatisfied conventional HA users. Subsequent to Tjellström's experiment in 1997, implantations started to include etiologies such as otosclerosis, radical mastoidectomy, failed ossiculoplasty/tympanoplasty, and atresia. Nowadays, the VSB, with more than 20 years of experience, is the oldest and most used middle ear implant worldwide. It is well acknowledged that the straightforward design and reliability of the transducer have certainly contributed to the success of the device.

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.

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.

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.

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.

[Asynchronous sequential stimulation. A new signal treatment for cochlear implants]. / Stimulation séquentielle asynchrone. Un nouveau traitement du signal pour les implants cochléaires.

Cochlear implants use a fixed or FO dependent stimulation rate, whatever the sound analysed (vowel or consonant) and its analysis procedure (fixed filters or FFT). We present a procedure which varies as a function of the nature of the input signal. This method is based on FFT analysis using a variable with analysis window. Short windows are applied on the transient part of the signal, providing poor frequency resolution but good time resolution; they accurately permit to 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 with an increase of the stimulation frequency. This strategy has been implemented using the Digisonic cochlear implant software, and clinically assessed on 6 regular cochlear implant users, owing to 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 are described and results presented.

Risk factors associated with AIDS in Haiti.

A total of 121 acquired immunodeficiency syndrome (AIDS) patients diagnosed in Haiti were studied between June 1979 and December 1983. Risk factors were identified in 65% of 34 patients evaluated in a standardized manner since July 1983 and included: bisexuality, 38%; blood transfusion, 21%; and intravenous drug abuse or a spouse with AIDS, 6%. These risk factors were reported by only 20% of the 85 patients studied between June 1979 and June 1983. AIDS patients also reported more frequent parenteral injections prior to the onset of their illness than control subjects (e.g., siblings, friends, sexual partners). Heterosexual activity among female AIDS patients was also greater than in their female controls. It was concluded that, in contrast to the experience reported among Haitians with AIDS in the USA, risk factors are present among most patients with AIDS in Haiti.

The acquired immunodeficiency syndrome in Haiti.

Two hundred twenty-nine patients in Haiti with the acquired immunodeficiency syndrome were studied between 1979 and 1984. The clinical spectrum of the syndrome in Haitians was similar in most aspects to that in patients with the disease in the United States. However, in contrast to findings in the United States, accepted risk factors (bisexuality, blood transfusions, intravenous drug abuse) were identified in only 43% of Haitian patients. Patients in Haiti with and without these risk factors were similar to each other but differed from age- and sex-matched siblings and friends in the number of heterosexual contacts and receipt of intramuscular injections. These latter activities were commoner in patients than in their siblings and friends, and represent potential modes of transmission of infection with the human T-lymphotropic virus type III.

Characteristics of the acquired immunodeficiency syndrome (AIDS) in Haiti.

To identify the characteristics of the acquired immunodeficiency syndrome (AIDS) as it occurs in Haiti, we studied 61 previously healthy Haitians who had diagnoses of either Kaposi's sarcoma (15), opportunistic infections (45), or both (1) established in Haiti between June 1979 and October 1982. The first cases of Kaposi's sarcoma and opportunistic infections in Haiti were recognized in 1978-1979, a period that coincides with the earliest reports of AIDS in the United States. We do not believe that AIDS existed in Haiti before this period. The types of opportunistic infections and the clinical course in Haitians with Kaposi's sarcoma and opportunistic infections were similar in most aspects to those in patients with AIDS in the United States. The median age of Haitians with Kaposi's sarcoma and opportunistic infections was 32 years, and 85 per cent were men. The interval between diagnosis and death was six months in 80 per cent of the patients. Diarrhea was the most common reason for seeking medical attention in patients with opportunistic infections. Lymphopenia and skin-test anergy were observed in 86 and 100 per cent of patients, respectively. Potential risk factors (bisexual activity or blood transfusions) were identified in 17 per cent of male and 22 per cent of female patients. Demographic information suggests that patients belonged to all socioeconomic strata of Haitian society.