Such sound dampers are generally known in the form of so-called earplugs which are manufactured from slightly flexible material and which, when arranged in the auditory passage, close it off entirely.

This causes discomfort for the wearer as a result of complete closure, whereby air pressure differences occur which are perceived by the wearer as being disagreeable.

In addition, an almost complete form of sound exclusion is obtained, so that a form of isolation results.

In order to obviate these problems sound dampers are also known wherein the carrier is provided with a channel extending in longitudinal direction which is provided with a constriction.

The problems of a complete closure and the resulting air pressure differences and complete sound insulation are herein avoided.

Experience has shown however that the dimensions of the constriction, i.e. the length and the diameter thereof, determine to a considerable extent the degree of sound damping.

However, in these prior art sound dampers the dimensions of the constriction depend to a great extent on the manner in which the sound damper is arranged.in the auditory passage. This can vary from person to person.

The object of the present invention is to provide a sound damper of the above stated type, wherein the dimensions of the constriction are defined precisely and wherein they are not subject to change.

This object is achieved in that the constriction is formed by a separate rigid disc is placed in the tube and provided with a hole with a defined diameter.

According to a first embodiment the carrier comprises an elongate tube and an envelope extending around the tube, wherein the envelope is adapted to adjust to the shape of the auditory passage such that the auditory passage is closed off by the envelope.

This step has the advantage that a single sound damper is suitable for everyone and does not have to be made to measure.

According to another preferred embodiment the disc is manufactured from ceramic material.

According to yet another preferred embodiment the disc is provided with a hole manufactured by a laser light beam.

Other attractive preferred embodiment are designated in the remaining sub-claims.

The present invention will be elucidated hereinbelow with reference to annexed drawing of embodiments, in which: figure 1 shows a cross-sectional view of a sound damper arranged in an auditory passage; figure 2 shows a cross-sectional view of a first embodiment of a sound damper according to the present invention; figure 3 shows a view similar to figure 1 of a second embodiment of the invention; figure 4 shows a cross-sectional view of the embodiment depicted in figure 3; and figure 5 shows an exploded view of the embodiment depicted in figure 4.

In figure 1 is shown a cross-section of a human ear 1 wherein a sound damper designated in its entirety by 3 is arranged in the external auditory passage 2.

The sound damper 3 is shown in more detail in figure 2. This shows that sound damper 3 is formed essentially by a tube 4 around which an envelope 5 is arranged and wherein a disc 6 is arranged in the interior thereof. The tube 4 is manufactured from relatively rigid plastic, wherein it can be manufactured for instance by means of an injection moulding method.

The tube 4 is provided on one side with a shoulder 7 which is chamfered toward the front. Arranged a short distance from shoulder 7 is a second shoulder 8, between which a groove 9 is created. On the other side of tube 4 is arranged a set of chamfers 10 and tube 4 is provided with a thickened portion 11.

The envelope 5 is manufactured from flexible material, i.e. material which is considerably more flexible than the comparatively rigid material from which tube 4 is manufactured. This flexibility provides the possibility for the envelope to adapt to the shape and dimensions of the external auditory passage 2.

For this purpose the envelope 5 is provided with an internal constriction 12 which fits into groove 9 and is there gripped fixedly between shoulders 7 and 8.

The envelope then extends outward at a greater distance from tube 4 and still further outward the envelope 4 once again comes closer to the tube. The envelope is herein provided with two internal ribs 13,14 which are engaged by the chamfers 10. On its outermost end the envelope 5 is provided with a ring 15 of relatively large diameter.

As already stated, the flexibility of envelope 5 results in the possibility of it adapting to the shape of the auditory passage. In the situation shown in full lines in figure 2 the envelope 5 is thus suitable for an auditory passage of relatively small diameter. For an auditory passage of somewhat larger diameter the envelope can be deformed to the situation shown with dashed lines.

For this purpose the sound damper 3 is introduced into the external auditory passage 2, whereafter pressure is exerted with the fingers against the disc 15 and this is moved inward, wherein ribs 13,14 slide over the chamfers 10 and fix themselves when no further pressure is applied to the ring. The user will herein continue pressing on ring 15 until a closure of the external auditory passage is obtained by the bulging envelope 5.

Further arranged in tube 4 is a groove 16 extending all the way round in which is arranged the disc 6 preferably manufactured from ceramic material. This dic 6 is provided with a hole 17 which is preferably arranged by means of a laser light beam. This provides the option of arranging a hole with an accurately defined diameter.

Instead of a disc of ceramic material it is possible to manufacture a disc from other types of material, for instance from metal, in which a hole is arranged for instance by means of drilling or other machining operation. However, in view of the precision required and the lifespan of the ceramic material, this latter material is recommended. It is noted herein that under prolonged pressure most materials yield so that when such materials are used for disc 6 there is a great likelihood of the hole 17 being deformed and the desired sound damping no longer being obtained.

It will be apparent that the thickness of the ceramic disc 6 is likewise of importance for the damping.

The thickness of the ceramic disc together with the diameter of the orifice can herein be used to determine the desired damping.

It is also possible to arrange several ceramic discs one behind another in series in the tube, as shown in figure 3. This provides an additional possibility of adjusting the damping.

In the embodiment shown in figures 3, 4 and 5 there is again question of a tube 21, in which a groove 22 has been provided, into which a disc 23 comprising an

aperture 24 has been located. At its outer side the tube 21 comprises a collar 25.

Further, this embodiment comprises an intermediate element 26 being formed of an annular body 27, to which a collar 28 is attached, but also a number of fingers 29 connected to the annular body 27 by a reduced part.

Further, the sound damper according to the invention comprises an envelope 30 made of soft material having a circle-symmetrical form and comprising a substantially cylindrical part 31, a substantially flat part 32 connected thereto, from which a part 33 has been removed, and a slightly conically part 34 being located concentric to the cylindrical part. At its end an aperture has been provided.

When this device is located in the auditory passage, the envelope 30 is provided around the intermediate element 26, after which the tube 21 is moved so far into the intermediate element 26 that it is clamped to some extent. Further, the combination thus formed is located in the auditory passage and is checked whether sufficient separation is obtained. If this is not the case the combination is removed from the auditory passage, the tube 21 is further pressed inwards, so that the fingers 29 will move in the outer direction, and the envelope 30 is diverted to the outer direction, so that the circumference thereof becomes bigger. Than it is newly fitted whether sufficient separation is obtained.

This process can be repeated several times until the correct separation and fixation is obtained.

Also in this embodiment a defined sound damper is obtained.

It will be apparent that diverse changes can be made to the embodiments shown without departing from the invention.