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T 174/21 – Sufficiency of disclosure: “One way” vs. “over the whole scope” – Ex officio examination by a board

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The patent relates to a method of processing a signal in a hearing aid, and to a a hearing aid.

Brief outline of the case

The opposition was rejected and the opponent appealed.

The board of appeal considered that the invention in claim 1 as granted could not be enabled over the whole range claimed. The same applied to AR 1-7 and the patent was revoked.

The board held that

  • there was a disclosure of “at least one way” but not over the “whole scope claimed”
  • it was entitled to raise objections ex-officio.

The decision is interesting in view of those two points.

The board’s decision

General considerations

The board considered that there are several influences that can impact the signal at the eardrum of the person wearing the hearing aid.

Firstly, the hearing instrument could suffer from an “acoustic leakage” after having been inserted into the user’s ear canal. Such an acoustic leakage causes the sound pressure at the eardrum to be lower than expected.

Secondly, the ear-canal wall typically dampens part of the sound emitted by the hearing instrument’s receiver.

Thirdly, any contaminations of the ear canal or eardrum, e.g. by cerumen, could also result in a decreased sound pressure at the eardrum. These influences should typically all be taken into account when fitting a hearing instrument.

It is, however, not always possible to measure the acoustic pressure at the eardrum. In those cases, the amplification characteristic of the hearing instrument is often measured outside the ear with a tube, “coupler”, connected to the receiver output. This tube simulates the ear canal.

In particular feature (c) of claim 1 was a key feature. Feature (c) reads: determining, from the acoustic signal and from a frequency dependent ear independent reference characteristics of the hearing instrument, an ear canal impedance.

Sufficiency of disclosure over the whole range claimed

With regard to feature (c) of claim 1, in order to be able to carry out the claimed invention over the whole range claimed, the skilled person in the field of hearing aids must in fact select a suitable “frequency-dependent ear-independent reference characteristic of the hearing instrument”.

This has to be done to determine the respective “ear-canal impedance” in order to then be able to calculate the “estimate of the acoustic transfer quantity” in accordance with feature (d).

The OD considered the opposed patent to specify “at least one way” to carry out the method of claim 1. However, this does not mean that the opposed patent discloses the claimed invention, i.e. the subject-matter of claim 1, in a manner sufficiently clear and complete for it to be carried out by the skilled person.

This is only the case if the “at least one way” covers, possibly augmented with the skilled person’s common general knowledge, the “whole range claimed“, cf. T 867/21, Reasons 3.2.

With reference to T 2773/18, the proprietor expressed some doubts as to the applicability of the “whole range claimed“-requirement in the field of audiology. However, the board considered that these doubts are unfounded. The board referred in this respect to the conclusions drawn in T 149/21, Reasons 3.4 and 3.6.

The board agreed with the opponent that the invention defined in claim 1 as granted is not sufficiently disclosed for the skilled person to carry it out over the whole range of the subject-matter claimed:

The claimed method of “estimating an acoustic transfer quantity representative of a sound pressure transfer to the eardrum of an ear” cannot be carried out for all kinds of frequency-dependent and ear-independent reference characteristics encompassed by feature (c).

In particular, a “microphone characteristic” constitutes one example of a hearing-instrument characteristic that is frequency-dependent and ear-independent but for which the claimed method cannot be carried out.

This is because a microphone characteristic will typically bear no information on how the ear canal actually impacts incident sound. Such information is however crucial when determining the “ear-canal impedance” in accordance with feature (c). As a result, a “microphone characteristiccannot be used to carry out the method defined in claim 1.

Ex-officio objection

The proprietor objected to the fact that the board had raised the issue ex officio. It was of the opinion that the board, as a judicial body, should refrain from doing so. Accordingly, it requested the board not to pursue this issue or to remit the case to the opposition division to decide on it first.

From a substantive point of view, the proprietor did not convince the board that this issue was “entirely new”. This is because the “determining” step in accordance with feature (c) of the “ear-canal impedance” by means of the “frequency-dependent ear-independent reference characteristics of the hearing instrument” was already challenged regarding sufficiency of disclosure in the first-instance proceedings.

This challenge was, as correctly noted by the proprietor, only substantiated by suggesting that the “acoustic signal” and the “frequency-dependent ear-independent reference characteristics” according to feature (c) alone were not sufficient to determine the “ear-canal impedance” in accordance with that feature.

Nevertheless, in the board’s view, the proprietor was informed that the “determining” step in accordance with feature (c) was potentially of a contentious nature. By providing this additional argument mentioned ex officio, the board merely illustrated this contentious nature by drawing upon its technical expertise to provide a concrete example of a “frequency-dependent ear-independent reference characteristics” in accordance with feature (c) for which the “determining” step according to this feature is not sufficiently disclosed.

Procedural aspects

From a procedural point of view, the board was not aware of any provision of the RPBA which could and would limit the powers and the duties provided for in Articles 114 and 111(1), respectively, in appeal proceedings.

The same applies in particular to Article 12(2) RPBA: this provision states that the “primary object of the appeal proceedings” is to “review the decision under appeal in a judicial manner”.

However, it does not limit the way in which the board is to carry out this review. Nor does it prevent the board from considering other secondary objects. Instead, this provision is primarily concerned with the obligations of the parties, not the board. Moreover, even if a provision of the RPBA were to limit the powers and duties of the board under Articles 111(1) and 114(1) to examine or raise an issue of its own motion, such a provision would not only be “incompatible with the spirit and purpose of the Convention”, see Article 23 RPBA. It would also be inapplicable.

The RPBA as “secondary legislation“, see Article 23(4) and Rule 12c EPC, can never take precedence over the provisions of the EPC itself.  

As regards the remittal of the case to the opposition division, the board noted that the ground for opposition under Art 100(b) has already been considered in the contested decision. The board therefore sees no “special reasons” within the meaning of Art 11 RPBA 2020 which could justify the proprietor’s request for remittal.


The decision reminds of important points of law and procedure.

Firstly, audiology is not a technical domain in which other rules apply when it comes to sufficiency.

Secondly, “one way” of implementing an invention does not mean that the invention can be implemented over the “whole range” claimed.

Thirdly, Art 114(1) does not limit deciding bodies of the EPO to the facts, evidence and arguments provided by the parties and the relief sought. It regularly happens that a board in its communication under Art 15(1) RPBA an objection not previously raised. This allows the proprietor to file under Art 13(2) RPBA a further request as the situation is exceptional and there are cogent reasons for filing a request during OP.

Fourthly, the board has the discretion to remit or not under Art 111(1) and/or Art 11 RPBA.

With the RPBA it has become accepted practice that a board only examines whether the decision was correct and anything not discussed in first instance can be disregarded. This certainly allows to increase the production/productivity of the boards.

Here, the point raised by the board was contentions from the beginning of the opposition procedure, and it is normal that the board went further than the OD.

Last but not least, one should not forget that the EPO should not maintain patents which have no reason d’être.

No amendment of the EPC by secondary legislation

It is further interesting to note that the board acknowledged that “secondary legislation” can never take precedence over the provisions of the EPC itself. 

In the OP for G 2/21, the representatives of the president repeatedly asserted that the EPC can be amended by secondary legislation. The board has strikingly refuted this allegation.

Actually, the only mechanism of amendment of the EPC is Art 174 and for the Implementing regulation it is Art 164(1).

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4 replies on “T 174/21 – Sufficiency of disclosure: “One way” vs. “over the whole scope” – Ex officio examination by a board”

francis hagelsays:

An example of Art 83 ex officio objection by a BOA in ex parte proceedings was provided in
T 161/18, a decision I have commented in epi information 2020-4. In this case, the BOA upheld the first-instance Art 56 rejection but added an Art 83 rejection for lack of disclosure of training data in an AI application. The BOA’s reference to Art 83 in the summons was not addressed by the applicant, who filed no comments and did not attend the OP, as stated in Reason 2.3.

It is in my view fully appropriate for a BOA to raise an Art 83 objection ex officio. The EPO is not supposed to grant patents which lack a sufficient disclosure, the requirement for a sufficient disclosure is a public policy objective.

Avatar photoDaniel X. Thomassays:

Dear Mr Hagel,

Thanks for your comment.

I would allow myself to observe that T 161/18 was on appeal after examination, hence the board could feel free to come with any further objection not raised by the ED.

In the present case, we are in appeal on opposition and the freedom of the board is limited by the considerations set out in G 10/91.

As the ground of lack of sufficiency was in the procedure from the outset and was relating to the “determining” step in accordance with feature (c) of the “ear-canal impedance”, the board worked within the boundaries of G 10/91. The proprietor overlooked the fact that the board upon appeal by the proprietor could well have a different view to that of the OD which had decided in favor of the proprietor.

In the board’s view, “the patent proprietor was informed that the “determining” step in accordance with feature (c) was potentially of a contentious nature. By providing this additional argument …… ex officio, the board merely illustrated this contentious nature by drawing upon its technical expertise to provide a concrete example of a “frequency-dependent ear-independent reference characteristics” in accordance with feature (c) for which the “determining” step according to this feature is not sufficiently disclosed”.

francis hagelsays:

Dear Mr Thomas,

Thank you for your answer.

I have looked at the string of decisions cited in your post : T 149/21 and T 867/21 in addition to T 174/21. It is to be noted that they were issued by the same Board 3.5.03 with only one different member in the panels of the three decisions and they all relate to inter partes proceedings with Art 100(b) submission by the opponent.

From a practitionner’s viewpoint, these decisions are to be given very serious consideration as to the disclosure required to support the entire scope of the claim. I find reason 3.3 of T 149/21 of particular interest in that it explains that the requirement applies to all technical fields, not only chemical/biotech.

As to T 161/18, it is to be distinguished from this string of decisions. It seems that in these cases, the issue of support for the whole scope of the claim could have been handled as an Art 84 objection during examination, whereas in T 161/18 the Art 83 issue related to the lack of disclosure of training data in an AI invention. Training data are known to be a critical component for the AI system to achieve its goal but the claim of the application merely included a general reference to training. As I see it, the issue was not whether there was support for the entire scope of the claim but the lack of enabling disclosure – a pure sufficiency issue.

Another difference was that in T 161/18, since the Board upheld the Art 56 rejection of the ED, they could have dispensed with raising an Art 83 issue. Which is why I saw in T 161/18 a clear signal to draw the ED’s attention on the sufficiency of training data in AI systems.

I take the opportunity to wish you a fruitful year 2024 and the successful continuation of your activities.

Avatar photoDaniel X. Thomassays:

Dear Mr Hagel,

Thanks for your further comments and you kind wishes for 2024. I intend to continue my activities. It goes without saying that I also wish you a fruitful year 2024 with a lot of satisfactions.

I agree with you that in T 161/18, there was a general lack of disclosure, and not merely a lack of disclosure for part of the range claimed.

In view of G 1/03 and T 2001/12 (confirmed by many following decisions) am not convinced that an Art 84 objection would have been correct in T 161/18.

If the application discloses essential features missing in the claim, then an objection under Art 84 is justified. The missing features can be added in the claim.

I use this distinction to prima facie discriminate between an objection under Art 83 and Art 84. With the proper indication in the original disclosure, an objection under Art 84 can be overcome. An objection under Art 83 can only be “overcome” by infringing Art 123(2).

If essential features are missing from the original disclosure, only an objection under Art 83 respectively Art 56 is possible.

I take from the catchword of T 2001/12, that the type of objection varies depending whether an effect is claimed or not.

If an effect is claimed and the original disclosure does not allow to achieve the effect, or the problem underlying the invention is not credibly solved for lack of data, then the objection is an objection under Art 83.

If it does not appear credible from the original disclosure that the invention as claimed would actually be capable of solving the problem, i.e. achieve a desired but not claimed effect, then the objection is an objection under Art 56.

In T 161/18 an effect was clearly claimed: determination of the cardiac output by using an equivalent aortic pressure transformed by a neural network. As the training data was missing, the neural network was not enabled. The objection under Art 83 was in my opinion the real objection. This effect was present in both claim 1 (method) and claim 8 (device).

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