CA2382309A1

CA2382309A1 - Hearing-protection device

Info

Publication number: CA2382309A1
Application number: CA002382309A
Authority: CA
Inventors: Zlatan Ribic; Hans-Rudolf Schiess
Original assignee: Individual
Current assignee: Individual
Priority date: 1999-08-19
Filing date: 2000-08-03
Publication date: 2001-03-01
Also published as: DE59903099D1; WO2001013840A1; ATE226054T1; EP1078615B1; AU6414500A; AU785494B2; EP1078615A1

Abstract

The invention relates to a hearing-protection device for deadening sounds, selectively based on frequency, comprising a housing which can be inserted into the external auditory canal of a person. Said housing contains a communication route for sounds, consisting of at least one chamber (26) and at least one channel (11; 23a, 23b, 23c, 23d) with a predetermined cross- sectional course which opens into said chamber (26). The invention is characterised in that a moveable element is provided which can be displaced into a multitude of positions, thus varying the cross-sectional course and/or the length of the channel (11; 23a, 23b, 23c, 23d).

Description

A hearing-protection device The invention relates to a hearing-protection device for damping sounds in a frequency-selective manner, comprising a housing which can be inserted into the external auditory canal of a person, said housing containing a transmission path for sounds, consisting of at least one chamber and at least one channel with a predetermined cross-sectional course which opens into said chamber.
Effective hearing protection is gaining increasing importance due to rising noise levels. It is necessary in many cases, however, not only to ensure an effective protection of the human auditory organ, but also to maintain the person's ability to communicate. These requirements can be fulfilled by hearing-protection devices whose damping behavior is frequency-dependent. The damping behavior is chosen in such a way that the damping is low in fihe range of the frequencies which is important for the ability to understand speech, whereas the damping in the specific frequency range of noise will be chosen as high as possible. In many cases, however, the noise to be deadened is situated in the low-frequency range.
In a number of cases, however, such as a tooth drill for example, high frequencies are concerned which need to be dampened in order to protect the ear. In the case of inadequate protection preliminary hearing losses will occur at first in which the threshold of hearing will regenerate again after a number of hours or days. In the case of continued noise exposition, a permanent hearing loss will occur which is also known as permanent threshold shift (PTS).
Generally, a hearing loss occurs at first in the range between 3 kHz and 6 kHz.
Subsequently, the hearing loss progresses in the range of high frequencies and only in the final phase also in the range of low frequencies. The healing of such hearing loss in the medical sense is not possible. That is why optimal hearing protection is of such importance.
A hearing-protection device is known from WO 91/11160 which is introduced into the ear and which is provided with one or several Helmholtz resonators. A
Helmholtz resonator is a combination of a chamber forming an oscillation volume with a canal opening into said chamber. In the electro-technical analogy the canal, depending on its diameter, forms an inductivity or a resistance, whereas the chamber corresponds to a capacity. A frequency-selective damping can be achieved in this manner depending on the geometrical dimensions of the individual components. It has been proven, however, that a damping behavior which is well suited for a certain kind of noise exposition offers unsatisfactory results in other applications.
A hearing-protection apparatus is known from DE 42 17 043 A which is also arranged in the manner of a Hslmholtz resonator. A protection from impulse-like noises with steep edges such as a bang is to be achieved with this kind of hearing-protection device in particular. The canal provided in the hearing-protection device can be closed by a suitable plug if need be, as a result of which the device can be changed over fram selective damping to general damping. In this case the ability to understand speech is considerably impaired.
Various documents such as AU 56067 73 A, US 2,327,620 A or US 2,881,759 A
describe hearing-protection devices in which a channel can be closed off by a valve or a seal in order to increase the damping accordingly. This allows choosing a low or high damping, as is required. A frequency-selective adjustment is not possible in this manner.
Yt is the object of the present invention to avoid such disadvantages and to improve a device of the kind mentioned above in such a way that an adjustment , to the various stress situations can be performed. This means that the frequency characteristics of the damping should be changeable depending on the expected noise exposition without impairing the speech intelligibility in an overly manner.
It is provided for in accordance with the invention that a movable element is provided which can be set in a plurality of positions in which the cross-sectional progress and/or the length of the channel is different.
The relevant aspect in the invention is that as a result of the chamber and the channel a Helmholtz resonator is formed whose geometrical conditions can be adjusted to the purpose of application. It is relevant in this respect, however, to realize a relatively low damping in a frequency range of 1. kHz to 3 kHz in order to maintain speech intelligibility. Musicians may under certain circumstances have other frequency ranges in which a low damping is desirable. The damping of the other frequency ranges is set by changing the cross-sectional progress of the channel. The change of the cross-sectional progress means that the channel which generally is not provided with a uniform cross section in the longitudinal direction can be set in such a way that the best possible damping behavior of the entire apparatus is achieved. The important aspect is that the channel is not simply closed off, but is changed instead in its cross-sectional. progress.
Generally, the channel has different sections with different cress sections and the adjustment to the desired progress of the transmission function is carried out by changing the cross-sectional progress by changing the length of the individual sections for example.
In a first group of embodiments this changeability of the cross-sectional progress is given in such a way that several channels are provided, of which one each is activated while the others remain closed off and thus deactivated.
In a preferred embodiment the movable element is formed as a rotatable drum which is provided with several channels of different cross-sectional courses, with the individual channels being covered or released by a fixed part of the housing depending on the respective position. In every operating position of the movable drum one of the channels is released by a bore in the housing, while the others are covered. In order to realize especially specific frequency curves it is theoretically also possible to release two or more channels simultaneously and thus to connect the same in parallel.
A particularly compact arrangement is given when the drum is arranged within the chamber.
It may be provided for in an alternative embodiment of the invention that several parallel channels are provided which are covered or released by the movable element. A constructional simplification can thus be achieved in a number of cases, It is preferably provided for that several parallel channels are provided which are covered or released by the movable element.
In a further preferred embodiment of the invention, a continuous changeability of the cross-sectional progress or the length of the channel is provided for. In contrast to the above embodiments, the changeover is not made discretely between the individual channels, but the cross-sectional progress is changed continuously. A particularly fine adjustment is thus possible.
A particularly high damping effect is achieved when in the state of operation the chamber is connected via a first channel with the hearer's auditory canal and is connected via a further channel with the ambient environment.
A high effectiveness in combination with the possibility of cost-effective production can be achieved in such a way that the channel consists of three sections which are disposed behind one another, with the middle section having a smaller cross section than the other sections. It is especially appropriate when several parallel channels are provided which substantially differ from one another by the length of the middle section.
The above embodiments are primarily suitable to realise a controllable damping in the low-frequency range. A particularly effective control in the high-frequency range is possible when a membrane is provided in the chamber transversally to the transmission path. A suitable membrane will allow sound of low frequency to pass with a relatively constant damping, whereas in the range around the resonance frequency the damping is substantially controllable.
The invention is now explained in closer detail by reference to the embodiments shown in the drawings, wherein:
Fig. ~, schematically shows a general hearing-protection device on which the invention is based;
Fig. 2 shows a circuit diagram which describes the behavior of such a hearing-protection device;

Fig. 3 shows a schematic representation to explain how such a hearing-protection works;
Fig. 4 shows a circuit diagram in connection with Fig. 3;
Fig. 5 shows a diagram which shows the damping behavior of a device according to Fig. 3;
Fig.6 shows a further schematic representation of another embodiment;
Fig. 7 shows a circuit diagram in connection with Fig. 6;
Fig. 8 shows a diagram according to Fig. 5 for the embodiment according to Fig. 6;
Fig. 9 shows a longitudinal sectional view through an embodiment of the present invention;
Fig. 10 shows an axonometric exploded view of the embodiment according to Fig. 9;
Fig. 11 shows a sectional view through a drum of the embodiment of Fig. 9;
Figs. 11A, 11l3, 11C, 11D and 11E show sectional views acCOrding to lines A-A, B-B, C-C, D-D and E-E, respectively, in Fig. 11;
Fig. 12 shows a sectional view through a further embodiment of the invention;
Fig. 13 shows an axonometric exploded view of the embodiment of Fig.
12;

-6~
Fig. 14 shows a further embodiment of the invention in a sectional view;
Fig. 15 shows a front view of the embodiment of Fig. 14, and Fig. 16 shows a partial representation of a further embodiment in a sectional view.
Fig. 1 shows the general arrangement of a hearing-protection device according to the state of the art. A housing 1 is arranged in its shape either in such a way that the device can be introduced into the external auditory canal or the housing is integrated in. a respective matching part (not shown herein) in order to achieve the optimal adjustment to the respective anatomical conditions. The sound waves arriving according to the arrow 2 pass through a net 3 into a first chamber 4. The chamber 4 is closed off by a membrane 5 and the sound waves can leave the device into the interior of the ear through a further chamber 6 and an opening 7 according to the arrow 8. A suction volume h0 is connected with the further chamber 6 via channels 9 which influences the damping behavior of the device, Fig. 2 shows an electric equivalent circuit diagram for the device of Fig. 1 which describes the behavior of said device. The sound wave corresponds to an alternating voltage source U which is applied to a capacity C~ which is representative of the ear. A first resistor R is connected in series to the capacity Ce which represents the acoustic impedance of the net 3. An inductivity Lm, a resistor Rm and a capacity Cm are connected in series which represent the membrane S. The mass of the membrane is responsible for the inductivity, whereas the resistor Rm reflects the friction caused by membrane 5. The capacity Cm reflects the elasticity of the membrane 5.
A further inductivity l.r, a further resistor R" and a further capacity Cr are connected parallel to the capacity Cf of the ear. This corresponds to the channels 9 and the suction volume 10.
It is obvious that by making a respective choice of the geometrical conditions of the device of Fig. 1 and the kind of mass and the tension of membrane 7 it is _ 7 , possible to strongly influence the damping behavior of the device depending on the frequency. It is thus possible for example to set a substantially even damping behavior over a large frequency range. This damping behavior cannot be changed, however.
Fig. 3 shows the principal arrangement in a schematic view of an embodiment of the present invention which is substantially arranged as a low-pass filter in which the damping can be changed in the low-frequency range. In this case the following are provided behind one another: a channel 11 consisting of a first channel section ila with a small cross section and a second channel section 11b with a larger cross section, a volume 12, a further channel 13 and a volume 14' which is representative of the ear, It has been noticed that a channel with a smaller diameter is acoustically representative of a resistance, whereas a channel with a larger cross section is rather representative of an inductivity. The reason for this is that friction dominates in channels with a smaller cross section, whereas the oscillation processes of the air play a role in larger cross sections. In the frequency range of interest one can assume a cross section of approx. 0.5 mm to 0.8 mm, beneath of which it is possible to observe a resistance behavior and above of which the inductivity dominates.
The nature of the invention is to change the length of the channel sections 11a and llb in order to allow optimally adjusting the hearing-protection device to the respective needs.
Fig. 4 shows the respective circuit diagram in connection with Fig. 3. U again corresponds to the sound source, the resistor R~ corresponds to the first channel section 11a, the inductivity to the second channel section 11b, the capacity C~ to the volume 11, and the further inductivity to the further channel 13. C~ is again representative of the ear 14.
Fig. 5 schematically shows a damping diagram in which the initial sound level is entered over the frequency. Fig. 5 shows four curves 15a, 15b, lSc, 15d which represent the transmission behavior of the arrangement of Fig. 3 depending on the frequency. Curve 15a corresponds to an arrangement of Fig. 3 with a large length I of the first channel section 11a. The curve lSb corresponds to an - s -arrangemenk according to Fig. 3 with a smaller 1, whereas the curves 15c and correspond to an even shorter first channel section 11a.
Fig. 6 schematically shows another embodiment of the invention which is arranged as a filter which is controllable in the high-frequency range, comprising a channel hl, a membrane 126 and an ear volume 14. Fig. 7 shows the analogous circuit diagram, with R~ again corresponding to the resistance of channel 11 and the inductivity Lm, the capacity Cm and the resistor Rm again representing the electric analogon to the membrane 16. Fig. 8 again shows the curves 17a, 17b, 17c and 17d which correspond to the transmission behavior of the arrangement of Fig. 6 with a different length I of the channel 11. The curve 17a corresponds to the channel 11 with the largest length I, whereas curve 17d corresponds to channel 11 with the shortest length 1.
Fig. 9 shows the constructional arrangement of a first embodiment of the invention. A housing 1 is closed with a lid 20. A drum 32 is rotatabiy held in the housing 1, which drum is pressed by a spring 22 against the lid 20_ Several bores are disposed in the axial direction in drum 21, one of which, namely the one forming channel Z3a, is shown in Fig. 9. A bore 24 in the lid connects channel 23 with the ambient environment. Further bores 25 in the face side of drum 21 are used to twist drum 21 with a respective tool (not shown).
The space within the housing 1 and around the drum 21 forms a channel 26 into which channel 23a opens. A further channel 27 leads from chamber 26, which channel opens into the external auditory canal when the hearing~protection device is in use.
Fig. L0 shows an exploded view of the arrangement of the apparatus of Fig. 9 on a reduced scale. Zt can be seen that further channels 23b, 23c, 23d and a further channel (not shown) are arranged parallel to channel 23a.
Fig. 11 as well as Figs. 11A, 11B, 11C, 11D and ilE show the precise arrangement of the drum 21. Channel 23a in Fig. 7.1a is designed consistently.
with a comparably large diameter of 1.5 mm for example. The channel 23b which is parallel thereto comprises a middle channel section 23b' with a small diameter _g_ of 0.3 mm for example. The length of this channel section 23b is ID. The channels 23c and 23d are arranged similar to channel Z3b. The only difference is that the middle channel section 23c' or 23d' of reduced Gross section are provided with different lengths I~ or Id, respectively. The channel 23e of Fig. 11E
comprises a channel section z3e' whose length h corresponds virtually to the entire length of channel Z3e.
Fig. 12 shows a further embodiment of the invention in a longitudinal sectional view. An opening 28 is used for the outlet of the sound which has penetrated a membrane 29 which is disposed in a chamber 30 transversally to the direction of propagation of the sound. A drum 21 is provided upstream of the same, which drum is arranged in analogy to the drum of Figs. 9 to 11 with the difference that the spring Z2 is disposed outside of the drum 21. Five parallel channels 23a to 23e are also arranged in drum 21 of Fig. 12, as is shown in the exploded view of Fig. 13. The sound waves enter the device in accordance with the invention through an opening 32 in a further lid 31. The membrane 29 is sealed and clamped by an O-ring 33 with respect to the housing 1 and the lid 20.
Fig. 14 shows an embodiment of the invention in which in a housing of the embodiments of Figs. 9 to 11 and Figs. 12 and 13 are mutually combined and are disposed parallel with respect to one another. A detailed description of the arrangement is therefore not necessary. Since the two drums 21 can be adjusted independently from one another there is a substantially independent controllability in the high-frequency and low-frequency ranges. This allows an optimal adjustment to difficult conditions. If a simultaneously forced damping is required both in the low-frequency as well as the extreme high-frequency range, it is possible, instead of a parallel connection, to provide a series connection of two or several individual devices.
Fig. 16 schematically shows an embodiment in which a continuous adjustability is given. A substantially helically arranged groove 3S is milled into the housing 1.
The drum 27., which is held in a rotatable manner in housing 1, comprises on its outside circumference a single groove 36 extending in the axial direction. The sound can enter the helical groove 35 through an inlet opening 38 and can exit the groove 36 of drum 21 through an opening 39. Both openings 38 and 39 are - 1~ -disposed in the face side 37 of the housing 1 or drum ?l. Depending on the rotational position of the drum 21 the cross-over point 40 of the grooves 35 and 36 displaces and thus the length of the channel between the openings 38 and 39.
As in the other embodiments, the cross sections of the channels 35 and 36 can be designed differently in order to form the inductivity on the one hand and the resistance on the other hand.
'1"he present invention allows changing and optimizing the damping behavior of a hearing-protection device in a purposeful way depending on the respective requirements. The adjustment can be factory-set during production, which allows producing and offering a plurality of differently acting hearing-protection devices with one and the same device. Both production expenditure as well as expendiiture for stock keeping can thus be reduced considerably. It is also possible to set the damping behavior during use in order to take changed ambient conditions into account. This allows a particularly flexible setting to the respective noise conditions in a particularly advantageous way.

Claims

CLAIMS:

1. A hearing protection device for damping sounds in a frequency-selective manger, comprising a housing which can be inserted into the external auditory canal of a person, in which a transmission path for sounds is disposed, consisting of at least one chamber (26) and at least one channel (11; 23a, 23b, 23c, 23d) with a predetermined cross-sectional progress which opens into said chamber (26), characterized in that a movable element is provided in which several different channels (11; 23a, 23b, 23c, 23d) are provided which are covered or released by a fixed housing part depending on the respective position.

2. A hearing-protection device as claimed in claim 1, characterized in that the movable element is arranged as a rotatable drum (21).

3. A hearing-protection device as claimed in claim 2, characterized in that the drum (21) is arranged within the chamber.

4. A hearing-protection device as claimed in claim 1, characterized in that several parallel channels are provided which are covered or released by the movable element.

5. A hearing-protection device as claimed in one of the claims 1 to 4, characterized in that the channel (23a, 23b, 23c, 23d) consists of three sections which are disposed one after the other, with the middle section (23a', 23b') having a smaller cross section than the other sections.

6. A hearing-protection device as claimed in claim 5, characterized in that several parallel channels (23a, 23b, 23c, 23d) are provided which substantially differ by the length (l) of the middle section (23a', 23b').

7. A hearing-protection device as claimed in one of the claims 1 to 6, characterized in that a membrane (29) is provided in the chamber (30) transversally to the transmission path.

8. A hearing-protection device as claimed in one of the claims 1 to 7, characterized in that several chambers are disposed in parallel or behind one another in the transmission path.