EP0246970B1 - Hearing aid devices - Google Patents

Abstract

The invention relates to a hearing aid device in which the slices (s1, x2) of the electrical signal corresponding to each acoustic signal comprised respectively between 1500 and 3500 Hz and between 5000 and 7000 Hz, are transposed into compensation signals (S1, S2) comprised within two coupled ranges of separate low frequencies above the range 60 to 800 Hz, alone preserved without compensation. To preserve the timbres of the transposed sounds, the compensation signals are obtained by multiplying each slice (x1, x2) by itself or by a signal (x'1, x'2) deduced from this slice by amplitude equalization.

Description

The invention relates to hearing aid devices intended for deaf people and in which the sounds emitted in at least a portion of the acute spectrum, sounds normally inaudible to said deaf people, are transposed into other "compensating" sounds situated in the low zone. audible of the acoustic spectrum.

Certain devices of this kind have been proposed by the French patents No. 1,382,916 and No. ⁰ 2,494,988.

The object of the invention is, above all, to make the devices of the kind in question such that the sounds transposed by them in the low region of the spectrum include information relating not only to the height and the intensity of the sound signals to be perceived, but also to the tones or laryngeal components of these signals.

To this end, the hearing aid devices of the above kind also comprise, in a manner known per se, transducer means for transforming the acoustic signals to be processed into electrical signals, means for taking at least one particular section xi of order i, of each of these electrical signals, included in a predetermined range of high frequencies, that is to say corresponding to acute sounds, frequencies between between fi min and fi max, i being an integer between 1 and 3 and increasing in the same direction as the frequencies of the slots considered, means for developing from each of these slots xi a compensation signal Si included in a range of low frequencies, that is to say corresponding to bass sounds, frequencies between Fi min and Fi max, the low ranges corresponding to the different compensation sounds If being distinct from each other, means for adding the s different compensation signals Si thus developed and transduction means for transforming the sum signal thus obtained into a signal applicable to the deaf to be treated so as to be perceptible by him.

According to the invention, the hearing aid devices thus defined are characterized in that the means for producing each compensation signal Si comprise means for multiplying the corresponding signal slice x _i by a signal x 'i which is either identical to this signal slice x; or else deduced from the latter by amplitude equalization, so as to form a product signal Xi, and means for taking, from this product signal Xi, using a bandpass filter, the portion of said signal-product whose low frequency is in the frequency range Fi min to Fi _m ax, portion which constitutes the compensation signal If desired.

The applicants have in fact discovered that the product signals Xi considered comprise such portions at low frequency due to the properties relating to the products of the trigonometric lines.

It turns out that each of the signals x; can be broken down into a Fourier series, i.e. a multitude of sinusoidal components of the type ^a cos 2πft + b sin 2πft (1 formula in which and b denote constants and f, the frequency of oscillation of the component considered, frequency between the two limits fi min and fi max.

If we consider, in addition to the component which has just been defined, a second component understood by the same signal xi and defined by the formula a 'cos 2πf't + b' sin 2πf't (2), in which a 'and b' denote two other constants and f, the frequency of this second component, understood as f between the two limits fi min and fi max, and if we multiply these two components one by the other, the product shows not only terms in cos 2 π (f + f ') t and sin 2π (f + f) t but also terms in cos 2π (f + f') t and sin 2π (ff) t.

More generally, if we multiply the signal xi by itself, the product signal Xi shows sinusoidal components oscillating at almost all frequencies of the type ff corresponding to differences of any two frequencies included in the range of fi min at fi max.

Among the innumerable differences in frequencies thus defined, a certain number are necessarily in the low frequency ranges desired for the bass compensation sounds, and this is what made it possible to obtain such bass sounds, sounds fully respecting the temporal forms. high-pitched sounds to represent.

This respect for the temporal forms makes it possible to transpose to the bass not only the heights and intensities of the acute slices sampled, but also their timbres, which considerably increases the intelligibility of the sounds processed.

• - le nombre n des tranches de signal xi à fréquence élévée qui sont prélevées dans les signaux électriques à traiter est égal à deux, la première tranche étant comprise entre 1500 et 3500 Hz et la seconde, entre 5000 et 7000 Hz,
• - dans un dispositif selon l'alinéa précédent, les gammes de fréquences graves choisies pour les sons de compensation Si et S₂ sont respectivement de 800 à 1000 Hz et de 1050 à 1200 Hz,
• - dans un dispositif selon l'alinéa qui précède le précédent, les gammes de fréquences graves choisies pour les sons de compensation Si et S₂ sont respectivement de 800 à 1200 Hz et de 1250 à 1900 Hz.

In advantageous embodiments, use is also made of one and / or the other of the following arrangements:

• the number n of the high frequency signal slices xi which are taken from the electrical signals to be processed is equal to two, the first slice being between 1500 and 3500 Hz and the second between 5000 and 7000 Hz,
• - in a device according to the preceding paragraph, the ranges of bass frequencies chosen for the compensation sounds Si and S ₂ are respectively from 800 to 1000 Hz and from 1050 to 1200 Hz,
• - in a device according to the paragraph preceding the previous one, the low frequency ranges chosen for the compensation sounds Si and S ₂ are respectively 800 to 1200 Hz and 1250 to 1900 Hz.

The invention includes, apart from these main provisions, certain other provisions which are preferably used at the same time and which will be more explicitly discussed below.

In what follows, we will describe preferred embodiments of the invention with reference to the accompanying drawing in a manner of course not limiting.

Figure 1 of this drawing is a diagram of a hearing aid device established according to the invention.

Figure 2 is a triple sonogram for understanding the interest of the invention.

• - un microphone 1 propre à transformer chacun des signaux acoustiques A qu'il reçoit en un signal électrique E dont les amplitudes et fréquences sont proportionnelles à celles dudit signal A,
• - un filtre passe-bande 2 laissant passer toute la portion S_o dudit signal E dont la fréquence est comprise entre une première fréquence très basse Fo min de l'ordre de 60 Hz et une seconde fréquence Fo max qui dépend du degré de surdité à traiter et qui est généralement comprise entre 500 et 1200 Hz, étant par exemple de 800 Hz,
• - n voies électriques V; montées en parallèle sur le filtre 2 et propres à élaborer chacune un signal électrique de compensation Si, le nombre n étant un entier compris entre 1 et 3 et l'indice i, un entier compris entre 1 et n, limites incluses,
• - un additionneur 3 propre à faire la somme S des signaux So et Si,
• - et un haut-parleur 4 propre à transformer le signal électrique S en un signal acoustique B qui est exploité de toute façon désirable et en particulier appliqué à l'oreille d'un sourd.

The device considered comprises, in a manner known per se:

• a microphone 1 suitable for transforming each of the acoustic signals A which it receives into an electrical signal E whose amplitudes and frequencies are proportional to those of said signal A,
• a bandpass filter 2 allowing the entire portion S _{o of} said signal E to pass, the frequency of which is between a first very low frequency Fo min of the order of 60 Hz and a second frequency Fo max which depends on the degree of deafness at process and which is generally between 500 and 1200 Hz, being for example 800 Hz,
• - n electrical channels V; mounted in parallel on filter 2 and each capable of producing an electrical compensation signal Si, the number n being an integer between 1 and 3 and the index i, an integer between 1 and n, limits included,
• - an adder 3 suitable for summing S of the signals So and Si,
• - And a loudspeaker 4 capable of transforming the electrical signal S into an acoustic signal B which is exploited in any desirable manner and in particular applied to the ear of a deaf person.

• - un filtre passe-bande 5i propre à prélever, dans le signal électrique E, une tranche xi du spectre aigu inaudible aux sourds, l'ensemble de ces tranches xi comprenant les portions, de la parole, les plus utiles à l'intelligibilité de cette parole,
• - et des moyens pour élaborer des signaux de compensation Si à partir de ces tranches xi, signaux compris respectivement dans des gammes distinctes de fréquences basses correspondant à des sons audibles par le sourd.

In a manner still known per se, the channels Vi each comprise:

• a bandpass filter 5i capable of taking, from the electrical signal E, a slice xi of the acute spectrum inaudible to the deaf, all of these slices xi comprising the portions, of speech, most useful for the intelligibility of this word,
• - And means for developing compensation signals Si from these slices xi, signals included respectively in distinct ranges of low frequencies corresponding to sounds audible by the deaf.

It is more particularly to these latter means of preparation that the invention relates.

• - un multiplicateur 6; propre à multiplier la tranche x_i par elle-même ou par un signal épuré x'i obtenu à partir de x_i par égalisation d'amplitude, ce qui donne un signal-produit Xi,
• - et un filtre passe-bande 7i traversé par la seule portion, du signal-produit Xi, qui est comprise entre deux fréquences basses Fi min et Fi max.

Said means essentially comprise, for each channel Vi:

• - a multiplier 6; suitable for multiplying the slice x _i by itself or by a refined signal x'i obtained from x _i by amplitude equalization, which gives a product signal Xi,
• - And a bandpass filter 7i crossed by the single portion, of the product signal Xi, which is between two low frequencies Fi min and Fi max.

Each of these low frequencies is both greater than F _{o max} and included in the range of frequencies audible by the deaf person to be processed.

In addition, preferably, each time Fi max <F _{(i + 1)} min is chosen.

These are the outputs of the filters 7i which constitute the desired compensation signals Si.

The amplitude equalization indicated above consists in making the coefficients a, b, a 'and b' of formulas (1) and (2) above equal to 1.

It is obtained by causing the signal slices xi to be purified to pass through amplifiers with controlled gain (ACG) 8i.

Before being added to the signal S _o in the adder 3, the compensation signals Si can be amplified so as to take account of the fact that the range of low frequencies which defines the filter band of each of them extends on only a small portion of the entire acoustic spectrum: this is how the range of said range is for example of the order of 200 to 500 Hz while the acoustic spectrum considered is of the order of 8000 Hz .

The compensation signals Si produced by the multiplication and filtering mentioned above can only be harmonics of the signals x; who gave birth to them.

They are therefore synchronized temporally with the latter and vary strictly like them, and at the same time as these.

We therefore observe here an immediate transposition, in real time, of the sounds to be made intelligible, which presents an important advantage over hearing aid devices for which the processing of the acoustic sounds received leads to the deferred emission of other sounds developed at from at least one component of said received sounds.

In FIG. 1, it has been assumed that the number n of the channels Vi is equal to two.

The high sampling frequencies of the two sections xi and x ₂ are then advantageously included, respectively, in the range 1500 Hz (f ₁ min) to 3500 Hz (fi max) and in the range 5000 Hz (f ₂ min) to 7000 Hz (f ₂ max).

As for the compensation sounds Si and S ₂ , they are for example included respectively in the range 800 Hz (Fi min) at 1000 Hz (Fi max) and in the range 1050 Hz (F ₂ min) at 1200 Hz (F ₂ max ), which corresponds to a deep deafness for which the deaf is able to perceive only the sounds whose frequency is lower than 1200 Hz.

According to a variant, applicable to severe deafness, but less deep than the previous one, the compensation sounds Si and S ₂ sounds respectively included in the range 800-1200 Hz and in the range 1250-1900 Hz.

It is to this latter variant that the three compared sonograms of FIG. 2 correspond.

For each of these graphs, the frequency is plotted on the ordinate and the time corresponding to the emission of the sentence "of the units of sounds" has been plotted on the abscissa.

The top sonogram in Figure 2 is for normal hearing.

The middle sonogram b corresponds to what is heard by a deaf person not equipped with a prosthesis, that is to say to the portion, of the acoustic message considered, which is filtered above 800 Hz.

Finally, the bottom sonogram c corresponds to what a patient affected by severe deafness means equipped with a prosthesis according to the invention.

The vertical stripes represent the transients of the laryngeal components of the sounds, or "timbres" of these sounds.

We see that the invention makes it possible to incorporate into the artificially reconstituted bass sounds perceptible by the deaf, not only the "whistles" or acute components of the speech (corresponding in particular to the sounds in "z" or in "s"), but also the timbres of the vowels.

As a result of this, and whatever the embodiment envisaged, a hearing aid device is obtained whose constitution, functioning and advantages (in particular that of conferring automatically and instantly on the grave artificial sounds reconstituted the temporal characteristics or " timbres "natural sounds to be perceived) result sufficiently from the above.

As is obvious, and as already follows from the above, the invention is in no way limited to those of its modes of application and embodiments which have been more especially envisaged; on the contrary, it embraces all variants, in particular those in which the hearing aid devices considered would be arranged so as to correspond to each sound processed a signal still perceptible by the deaf to assist, but not necessarily acoustic, in particular a signal impulse applicable to said deaf person in any desirable manner perceptible to him, this application being carried out for example electrically on his auditory nerve, or even mechanically on his skin using an appropriate vibrator.

Claims (4)

1. Hearing aid device comprising transducer means (1) for transforming the acoustic signals (A) to be processed into electrical signals (E), means (5i) for sampling at least one particular slice x; of the order i of each of these electrical signals, comprised within a pre-determined range of high frequencies, that is to say corresponding to high- pitched sounds, frequencies comprised between fi min and fi max, i being an integer comprised between 1 and 3 and increasing in the same direction as the frequencies of the slices concerned, means for elaborating from each of these slices x; a compensation signal Si comprised within a range of low frequencies, that is to say corresponding to bass sounds, frequencies comprised between Fi min and Fi max, the bass ranges corresponding to the various compensation sounds Si being distinct from one another, means (3) for adding the different compensations signals Si so elaborated and transducer means (4) for transforming the sum-signal so obtained into a signal (B) applicable to the deaf person to be assisted so as to be perceptible by him, characterized in that the means for elaborating each compensation signal Si comprise means (6_i) for multiplying the corresponding slice of signal x; by a signal x' which is either identical with this slice of signal xi or deduced from the latter by amplitude equalization, so as to form a product-signal Xi, and means for sampling, in this product-signal Xi, by means of a band-pass filter (7i), the portion of said product-signal whose low frequency is comprised within the frequency range Fi _min to F; _max, which portion constitutes the desired compensation signal Si.

2. Hearing aid device according to claim 1, characterized in that the number of slices of signal xi at high frequency which are sampled from the electrical signals to be processed is equal to two, the first slice being comprised between 1500 and 3500 Hz and the second, between 5000 and 7000 Hz.

3. Hearing aid device according to claim 2, characterized in that the ranges of low frequencies selected for the compensation sounds S₁ and S₂ are respectively from 800 to 1000 Hz and from 1050 to 1200 Hz.

4. Hearing aid device according to claim 2, characterized in that the low frequency ranges selected for the compensation sounds S₁ and S₂ are respectively 800 to 1200 Hz and 1250 to 1900 Hz.

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