T 0109/82 (Hearing aid) 15-05-1984

1. The appeal complies with Articles 106 to 108 and Rule 64 EPC and is, therefore, admissible.

2. The citation introduced by the appellant (W. Güttner, Hörgerätetechnik, Georg Thieme Verlag, 1978, pages 26 and 27), which must be treated as the closest prior art, discloses a method of measuring and setting the maximum sound-pressure output of hearing aids by means of a measuring box in which a sound generator is acoustically connected with the sound inlet of the hearing aid under free-field conditions and the hearing-aid output is connected via the coupler with the (electro-acoustic) measuring device containing a resonance chamber. The measuring and testing device of Claim 1 differs from that above by virtue of a sleeve made of resilient material encircling the sound generator's sound opening. The sleeve's opening pointing away from the sound generator encloses and acoustically seals the hearing aid's sound inlet. A further feature is that the sound outlet of the hearing aid is connected with the coupler's resonance chamber via the individual ear adapter of the wearer. US-A 3 979 567, cited inter alia in the search report, discloses merely a coupler used for testing hearing aids including individual ear adapters. It does not indicate how sound is transmitted from sound generator to hearing aid. The other publications referred to in the search report and relating to devices of the kind claimed are still less germane to the application's subject-matter than those already mentioned. The stethoscope according to the leaflet of Kirchner & Wilhelm, introduced in the appeal proceedings and clearly in prior use, is fitted with rubber sleeves which insulate against extraneous noise. It is not therefore a device of the kind represented in Claim 1's precharacterising portion. Having examined the state of the art referred to, the Board has come to the conclusion that a device for measuring, testing and in particular setting the maximum sound-pressure output of a hearing aid with all the features stated in the present Claim 1 according to the main and alternative requests is not known in the state of the art as ascertained in this case. Consequently the subject-matter of the said claims is new vis-à-vis that state of the art (Article 54 EPC).

3. The closable measuring box, used according to the cited literature by Güttner, containing a large sound-insulated closed chamber, receives the hearing aid to be tested during the test and is exposed by a sound generator to an audio signal at an approximately constant level. The level is raised by means of the adjustable amplification of the hearing aid and is read off a meter. However, precise setting of the maximum sound-pressure output requires multiple opening and shutting of the measuring box in order to adjust the setting to the specified measurement value. The appellant considers the use of such an expensive measuring box and the considerable amount of time required to conduct the measurement as disadvantageous.

4. Consequently the appellant sees the problem to be solved by means of Claim 1's subject-matter as being one of designing a device of the said type with which the hearing aid can be measured and tested in a simplified way without the cumbersome measuring box and with the time required being reduced.

5. It is therefore necessary to establish whether a device according to Claim 1 is obvious from the state of the art cited. The following factors emerge as a result:

5.1 According to the appellant, hearing aids have been tested and measured for many years by means of costly and cumbersome sound- measuring boxes, without it ever occurring to a person skilled in the art to simplify that measuring process, for example by dispensing with the box. On the strength of this uncontested fact the appellant believes it can be concluded that to pose the problem must itself be considered as a contribution to inventive step. The latter should thus not be determined exclusively from the solution according to the features of Claim 1. However, common sense dictates that the deficiency represented by the cumbersomeness of the elaborate measuring box would not have escaped the notice of skilled persons in view of practical experience gained from constant use of it when measuring, testing and setting hearing aids. If a skilled person establishes that for that kind of method an elaborate measuring box was considered necessary because acoustically intricate measurements had to be made during development work to determine transmission characteristics of hearing aids, but that in the case of less intricate measurements, such as the commercial testing and setting of hearing aids by a hearing-aid acoustician, the elaborate process of sound conduction in a free sound field with advancing plane waves is not considered justified, it becomes clear that to pose the problem to be solved here must be regarded as merely a consequence of the deficiencies identifiable in practice which logically leads to a search for a solution to eliminate them. In the circumstances this problem could therefore readily have been posed by any skilled person when and if the need had arisen. It is thus in no way remote and must therefore be regarded as obvious to the skilled person. In that case it is unable to make a contribution towards the inventive merits of its solution. The arguments put forward by the appellant to support an inventive contribution in posing the problem thus cannot be conceded.

5.2 The aforementioned citation from the literature (W. Güttner, Hörgerätetechnik) deals with an intricate measuring technique whereby in the measuring box both a microphone calibrated to a sound-free field and also the hearing aid to be measured are disposed symmetrically in relation to the sound generator's axis. As stated under 5.1, however, an expert acoustician can readily see that to conduct less intricate measurements a free sound field requiring a large chamber can be dispensed with and the sound inlet of the hearing aid can be irradiated direct and from a short distance. The skilled person does of course have the alternative of using a measuring box appropriately reduced in size. However, this would not overcome the deficiency of repeated opening and shutting. The other alternative available to the skilled person of dispensing with the box altogether has to be dismissed as unsuitable because of the interfering extraneous noise. A skilled person is therefore forced to work towards a solution whereby the sound conduction concentrates as much as possible on the inlet with the surrounding area being simultaneously screened off. This finding leads to the question as to whether suitable sound conduction devices are known in other fields which can meet those requirements. For the most part, such fields involve devices for direct sound conduction. One such field is indoubtedly that of medical hearing apparatus of the stethoscope variety. As is clearly shown in the cited leaflet of Kirchner & Wilhelm, Stuttgart, it is known in that field how, by means of funnel-shaped rubber sleeves, to transmit sound emitted by the human body via an inlet adjoining the sleeve. The stethoscope described there under the designation "Petiphon" (Cat. No. 43521) contains inter alia a clear reference to a freely vibrating funnel-like rubber sealing ring which moulds onto uneven parts of the body completely screening off extraneous noise. This teaches the direct conduction of sound beamed at a sound inlet by means of a rubber sealing ring identical in construction and function with the rubber sleeve according to the application. Since Kirchner & Wilhelm confirmed, when asked, that such stethoscopes were already in supply prior to 1978 and the appellant has not contested the accuracy of that statement, it must be assumed that this stethoscope belongs to the state of the art. Consequently it must be taken into consideration when assessing inventive step. As a result it was quite possible for an acoustician confronted with the problem of sound conduction beamed at a sound inlet to obtain the knowledge required for solving the problem at hand. To apply the teaching given there between the sound generator and the microphone opening of a hearing aid is hence obvious and produces no surprising effect, merely one that could be readily anticipated.

5.3 The appellant's objection that to test hearing aids in accordance with the stethoscope model would not achieve the desired purpose, because the rubber ring would in that case logically have to be fastened to the hearing aid's sound inlet, cannot prevail. Any skilled person should be aware that the hearing aid to be tested has no sleeve at the sound inlet and that this is an essential part of the testing equipment. The idea of fastening it to the sound generator and switching the mounting side is thus thrown up by the nature of the system. In view of the unchanged sound conduction direction, it is also completely irrelevant in physical terms and represents merely an indispensable, but purely mechanical measure.

5.4 Similarly, the feature remaining in Claim 1's characterising portion and in fact already known (cf. US-A-3 979 567), whereby the sound outlet of the hearing aid is connected with the resonance chamber via the individual ear adapter of the wearer, must also be regarded as being obvious. Considering that the individual ear adapter of the wearer, necessarily belonging to the hearing aid, has long been taken into account by all hearing-aid acousticians in the conventional type of measurement, retention of that ear adapter on the associated hearing aid when conducting a test using a sleeve does not produce a change in the sound conduction function. This feature cannot make an advantageous contribution vis-à-vis what is already known. Nor, as any skilled person can also see, does this feature contribute to solving the problem posed, since its solution lies solely in the special type of sound conduction onto the inlet of the hearing aid, without the individual ear adapter being able to have any kind of positive effect on the sound conduction there. It follows that each of the characterising features operates in a normal manner without any mutual interaction. It is therefore a question of a collocation of features which do not support each other in terms of effect but merely achieve a cumulative effect and must therefore be considered as being obvious.

5.5 The appellant also claims that, despite the cumbersome sound-measuring box having been in use for decades with all its shortcomings, no person skilled in the art has ever hit on the idea of doing without it - a sure sign that the invention was not obvious. However, the appellant overlooks the fact that the time factor cannot be the sole yardstick. Such a conclusion is admissible only if non-obviousness is supported by other concurrent factors. One such factor is undoubtedly an urgent need which has not been met over a long period of time. Where such a need does not exist, experts in a particular field have no cause to deviate from conventional methods and break new ground. Precisely in view of the fact that the state of the art has clearly been inactive over a long period and the absence of indications in the entire prior art as disclosed of attempts or efforts to omit the measuring box, the Board concludes that such a need does not exist, particularly since the appellant has failed to provide evidence to the contrary.

5.6 For the above reasons the subject-matter according to Claim 1 of the main request is obvious. It thus does not involve an inventive step (Article 56 EPC) and this claim cannot therefore be allowed (Article 52(1)).

6. The aspects referred to with respect to the novelty and inventive step of Claim 1's subject-matter according to the main request apply in turn also to the device according to Claim 1 as set out in the alternative request. Claim 1's subject-matter according to the alternative request therefore also does not involve an inventive step (Article 56 EPC) and thus cannot be allowed either (Article 52 EPC). Consequently it is not necessary to establish whether Claim 1's contested lack of clarity is removed as a result of the proposed insertion.

7. Claims 2 to 5 are dependent on the non-allowed Claims 1 according to the main and alternative requests and are therefore likewise disallowed.