US3798393A

US3798393A - Headphone construction

Info

Publication number: US3798393A
Application number: US00231762A
Authority: US
Inventors: R Gorike
Original assignee: AKG Akustische und Kino Geraete GmbH
Current assignee: AKG Acoustics GmbH
Priority date: 1969-02-17
Filing date: 1972-03-03
Publication date: 1974-03-19
Anticipated expiration: 1991-03-19
Also published as: NL7001438A; FR2031469A1; DE2006249A1; GB1301014A

Abstract

A headphone construction includes freely radiating sound converters whose diaphragms, when the earphones are attached, are not loaded by the impedance of the wearers'' ear. The diaphragm of the electrostatic converter is primarily mass-inhibited and damped by acoustic or mechanical friction resistances. Supporting elements are provided between the head and the earpiece which provide minimum spacing distance between the diaphragm and the inlet of the ear which corresponds practically to the contactfree wearing of the sound converters. The supporting elements may advantageously comprise a pair of ring members which are concentrically arranged one within the other around the ear and which support the earphone at a spaced location from the ear. The rig members include openings which may be aligned and enlarged for varying the opening space defined between the diaphragm and the ear opening.

Description

United States Patent 1 1 3,798,393

Gorike Mar. 19, 1974 [54] HEADPHONE CONSTRUCTION 3";1120'05 11/1963 Shaw et al. 181/23 3.157.750 11/1964 Weingartner 179 1155 R [751' Inventor: Rudolf Gorike, Wien, Austria [73] Assignee: Akg Akustische u. Kino-Gerate Gesellschatt m.b.H., Wien, Austria [22] Filed: Mar. 3, 1972 [21] Appl. No.: 231,762

Primary Examinerl(athleen H. Claffy Assistant Examiner-Thomas L. Kundert Attorney, Agent, or Firm-McGlew and Tuttle [57] ABSTRACT A headphone construction includes freely radiating Related US. Application Data sound converters whose diaphragms, when the ear-.

[63] Continuation of Ser. N0. 10,868, Feb. 12, 1970, Phones are attached, are not loaded y the impedance abandoned. of the wearers ear. The diaphragm of the electrostatic converter is primarily mass-inhibited and damped by Fm'eign Application m' y Data acoustic or mechanical friction resistances. Supporting Feb. 17, 1969 Austria ..l583 A/69 elements are provided between the head and the ear- .Ian. 12,1970 Austria ..243 A/70 piece which provide minimum spacing distance bet W 5 tween the diaphragm and the inlet of the ear which [52] US. Cl. 179/182 R, 179/180 corresponds practically to the contact-free wearing of [51] Int. Cl H04r 1/10 the sound converters. The supporting elements may Field Search-m 115-5 advantageously comprise a pair of ring members 179/156; 181/23 which are concentrically arranged one within the other around the ear and which support the earphone [56] References Cited at a spaced location from the ear. The rig members UNITED STATES PATENTS include openings which may be aligned and enlarged 3.586.794 6/1971 Michaelis 181/23 varying the Opening defined between the 2.363.175 11/1944 Grossman 181/23 aphragm and the ear openmg- 8 Claims, 3 Drawing Figures PATENIEUMAR 19 I974 FIG.I

INVENT OR.

Ruben G6'RIKE Wfu 7f Em.

FI'ITORNEYS HEADPHONE CONSTRUCTION This is a continuation, of application Ser. No. 10,868, filed Feb. 12, 1970 now abandoned.

SUMMARY OF THE INVENTION This invention relates in general to the construction of earphones and in particular to a new and useful earphone with a freely radiating sound converter having a diaphragm which is not loaded by the impedance of the ear when the earpieces are attached over the ear and they are primarily mass-inhibited and clamped by acoustic or mechanical friction resistances, and wherein supporting elements are provided for the earpieces for holding the diaphragm at a minimum spacing distance from the diaphragm inlet to the auditory cancal of the ear of the wearer.

Head phones which include earpieces which do not have to fit tightly on the ear are known as earpieces of the first order or as open earpieces. These are earpieces whose diaphragms are not exposed to the full damping effect of the impedance of the outer auditory canal, but a lower impedance appears as a damping element for the diaphragm, depending on the degree of loose fit or of the. partlypermeable soft padding between the ear and the earpiece. Such an arrangement involves a change in the frequency course of the sound pressure of the ear particularly a loss of low frequencies. It has been attempted to reduce the resonance frequency of the small diaphragms by loading by means of an acoustic mass arranged in one or several narrow bores. But in such an arrangement disturbing resonance peaks appeared in the range of higher frequencies.

In accordance with the present invention, there is provided a head phone or ear piece having a sound converter which operates in the manner of a loud speaker with a freely radiating diaphragm. No use is made of the damping effect of the ear impedance but the vibration mechanical properties of the sound converter are influenced by dampings in the converter. The invention provides an improved means for mounting the ear piece and for arranging the converter adjacent the ear. The diaphragm is damped so that it provides, in the entire bearing range with constant flow through the moving coil, a constant sound pressure at the ear entrance. This is accomplished by utilizing the physical laws of free radiating diaphragms and the results of the investigations for radiators of the first order in the close range field of spherically propagating sound waves, and the sound propagation of small diaphragms compared to wave length and which are connected at the ear to a closed cavity or so-called box. The sound converters are arranged in front of the auditory canal at a certain spacing so that the effect on the ear is so perfect that the natural quality of language or music is preserved. This arrangement has the advantage that the listener maintains the contact with the surrounding space and it is not important that noises exist but that the unconscious space impression of the environment is effective. The absence of the termination of the ear and of the other outer auditory canal, enhancing the transpiration, represents a progress.

For the realization of the invention the converters must be designed in a different manner than heretofore. The small diaphragm of metal or plastic or a combination of these materials must have a very flexible bearing so that the resonance frequency is in the range of the lowest frequencies preferably between 50 and Hz. The damping of the diaphragm is extremely critical because it alone is determinant for the acoustic effect on the ear. The damping must not cause any resonances by the formation of cavities and must be ohmic to a great extent.

By mass-inhibition we understand a certain ratio of the amplitude of the diaphragm relative to the current flowing through the moving coil as a function of the frequency. Mass-inhibition exists when the amplitude at the diaphragm increases at constant current as a square function with decreasing frequency. The resonance frequency is of the diaphgram must be at the lower limit of the transmission range as it is known in freely radiating loud speakers. With small diaphragms of from 3 to 5 centimeters in diameter as required for head phones the requirement for a low tuning of the diaphragm results in an extremely flexible support for the diaphragm. In order to meet the required amplitude ratio, the damping of the diaphragm must be effected very accurately by means of acoustic frictional resistances. Insufficient damping allows the diaphragm to permform excessive amplitude in the resonance frequency which causes the diaphragm or the moving coil to strike against the magnet system or causes their mechanical destruction. Excessive damping has the effect that the state of vibration of the diaphragm changes from massinhibition to friction inhibition which manifests itself in a loss of bass reproduction in the head phone. The damping must be just enough so that a resonance super elevation is prevented and the law for mass-inhibition is satified. v

In order to avoid any cavity resonances between the diaphragm and the ear damping material, for example, foam, can be arranged in front of the diaphragm but it must not bear, however, on the ear in order to avoid an accumulation which could lead to the formation of sweat. The damping material must also be so selected and arranged that the effective sound does not undergo any substantial weakening particularly of the frequency dependent type.

In accordance with the invention, the construction of the mount of the converters, can be such for example, that the head band bears above both the ears on the head and the converters are suspended on the band or ear pieces can be provided which have wide openings through which the cavity formed at the ear is in communication with the outside air. The openings serves at the same time for ventilation which is desirable for health reasons. In a modification of the, construction, the openings are defined by two concentrically arranged spacing rings having oblong arcuate slots which may be shifted relatively or aligned in order to selectively define the degree of opening which is obtained. The changing of the sizes of the openings by the degree of alignment of the two oblong slots provides different acoustic effects. If the openings are not closed the converters work like freely radiating loud speakers and the ear works in the close range of the diaphragm. If the openings are closed, the impedance of the outer auditory canal has a damping effect on the diaphragm so that the mass-inhibited diaphragm becomes primarily a frictional-inhibited diaphragm.

Accordingly, it is an object of the invention to provide an improved head piece which includes an electrostatic converter having a diaphragm mounted in a housing which is spaced from the ear by means which permits the opening of the ear to the surrounding air and which advantageously also includes damping means disposed between the diaphragm and the ear.

A further object of the invention is to provide an earpiece or head phones with freely radiating sound converters having diaphragms which are not loaded by the impedance of the ear but are primarily mass-inhibited and clamped by acoustic or mechanical frictional resistances and which include means for supporting the diaphragms so that a minimum spacing between the dia phragm and the inlet to the ear is ensured which will correspond to contact-free wearing of the sound converters.

A further object of the invention is to provide an earpiece which is simple in design, rugged in construction, and economical to manufacture.

The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which there are illustrated and described preferred embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a schematic sectional representation of an earpiece constructed in accordance with the invention;

FIG. 2 is a view similar to FIG. 1 of a slightly modified embodiment; and

FIG. 3 is an enlarged view similar to FIG. 1 of the preferred embodiment of the invention.

GENERAL DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings in particular, the invention embodied therein in FIG. 1, comprises an earpiece including a cup-shaped housing 2 for an electrostatic converter preferably an electrodynamic system 1 which is supported therein and which includes a diaphragm 3 shown in dotted lines. In accordance with the invention in order to prevent the earpiece from bearing directly on the ear supporting means in the form ofa supporting element or a plurality of such supporting elements 4 are provided to space the housing opening 9 away from the auditory canal opening 5 of the ear of the wearer. The individual supporting elements 4 hold the housing 2 so that a minimum distance of several milimeters between the edge 8 of the housing and the auditory canal 5 is maintained.

In the embodiment illustrated in FIG. 2, a housing 2 of similar construction carries an electrostatic converter 1' having a diaphgram 3 and it includes an opening 9' which is held at spaced orientation from the ear by supporting means 4' as in the other embodiment. In this construction, a clamping material 6 is interposed between the opening 9' and the auditory canal'5. The damping material 6 has the form of a cylindrical disc which may also be of conical configuration in which the thinnest point, or the apex of the cone, is at the center of the diaphragm. It is important that the damping material must not bear directly on the ear since the latter is a poor heat conductor and would cause an accumulation of heat which would lead to the formation of sweat.

In accordance with the preferred form of the invention indicated in FIG. 3, the support means 4 comprises a ring structure instead of the individual cylindrical plugs 4 as employed in the embodiment of FIG. 1. A support means includes a ring shaped chasis 21 which is secured at a flange of a housing or cap 18 and which is preferably made of a material such as plastic. The ring-shaped chasis 21 includes a plurality of openings or oblong slots 23 which may be selectively aligned with similar oblong slots 25 of outer ring members 24 which are rotatably supported between a ledge portion of the ring member 21 and the flange of the cap 18. An ear fitting member is secured to the chasis 21 and it includes a bulbous portion 22 which can be filled with a liquid or a foam material. Variation in the size of the openings defined by the two

separate slots

23 and 25 may be made by rotating the outer ring 24 relative to the chasis 21, so that it is possible to vary the ventilation of the space created between the earpiece diaphragm and the ear and also to provide variation characteristics.

In order to damp any cavity resonances that appear, a sound transmitting foam cushion 6' is arranged on a guard or grill 10 in front of the diaphragm 3". The drive of the diaphragm 3" which is suspended on a soft mounting 28 is conducted through a centering diaphragm 9 and is effected preferably by an electrodynamic converter system consisting of a magnet 11 and a bolt 12 as well as a front magnet plate 13 and a rear magnetic plate 14. A vent duct 15 in the bolt 12 leads from the central portion of the diaphragm 3" to the outside and into the chamber enclosed by the cap 18. The diaphragm parts which are arranged on the outside coil 16 are in communication with this chamber enclosed by the cap 18 through the vent hole 17. The cap 18 is provided with openings 19 to establish communication with the outside air. The cap 18 carries a journal 20 at the diametrically opposite sides which provide means for mounting the headpiece on a head set band (not shown). The chamber defined within the cap 18 may advantageously be filled with a damping material.

A head phone constructed particularly as indicated in FIG. 3 may be made relatively large but maintained very light, easy and pleasant to use, and it will not exert a continuous annoying pressure on the ear. The effect achieved by the use of a head phone of this nature is characterized by a sound similar to that listening to a loud speaker production in a room since the room noises can also be heard through the distance pieces and the impressions of being isolated, as is the case with conventional earphones, is eliminated. Due to the fact that a converter is provided at each ear, stereophonic performances can be transmitted very clearly and much simpler than with the loud speakers and with substantially less electric power being required at the output of the amplifier while the usual sound pattern and the impression is maintained.

What is claimed is:

1. A headphone having a completely free sound radiation, and including a sound converter with a diaphragm which, with the headphone mounted adjacent a wearer's ear, is free of loading by the impedance of the ear, said headphone comprising, in combination, a housing; an electro-acoustic converter in said housing having a freely radiating, primarily mass inhibited and damped, diaphragm, with a natural resonant frequency in the range of the lowest sound frequencies; said housing having an opening on one side of said diaphragm for sound transmission'from said diaphragm to the entrance to the auditory canal of the wearers ear; and rigid supporting means extending from the periphery of said housing opening for supporting said housing at the wearers ear, free of engagement with the ear at and around the auditory canal, with the opening of the housing spaced a fixed distance from the wearers ear to provide a minimum distance between the diaphragm and the entrance to the auditory canal of the wearers ear corresponding to completely contact-free wearing of a sound converter, and defining a large air volume cavity between said diaphragm and the entrance to the auditory canal providing a loose coupling between said electroacoustic converter and the auditory canal; said supporting means defining a plurality of open spaces providing communication between said large air volume cavity and the outside air, and also providing unhindered circulation of ventilating air between the headphone housing and the wearers ear; said low frequency resonant diaphragm compensating for the loss of low frequencies resulting from such loose coupling between said electro-acoustic converter and the wearer's auditory canal due to said supporting means.

2. A headphone, according to claim 1, wherein said supporting means comprises a radially narrow ring member connected to said housing and spacing said opening and said diaphragm at a fixed distance from the auditory canal, said ring member having plural openings to the atmosphere.

3. A headphone, according to claim 1, wherein said supporting means comprise a plurality of individual elements spaced around theperiphery of said housing opening, and including a dampening material located adjacent said opening between the diaphragm and the ear and spaced from the ear.

4. A headphone, according to claim 1, wherein said supporting means comprises radially narrow ring means holding said housing opening and the diaphragm at a spaced location from the ear and including one apertured ring member movable relatively to another for defining openings to the atmosphere of varying size.

5. A headphone, according to claim 1, wherein said supporting means comprises a radially narrow ringshaped supporting element engaged around said housing around the opening thereof, said supporting element having a bulging annular edge portion of soft material on its narrow outer edge for fitting against the ear.

6. A headphone, according to claim 1, including a sound damping material disposed over said diaphragm between the diaphragm and the ear and spaced from the ear, said supporting means comprising a radially narrow ring member having openings, and means associated with said ring member for varying the size of the openings and for closing the openings.

7. A headphone, according to claim 4, wherein said supporting means includes first and second ring members each having a slot therethrough, said ring members being relatively rotatable for aligning at least a portion of the slots of each ring member, the aligned slots being enlargeable to vary the opening size.

8. A headphone, according to claim 6, wherein said sound dampening material comprises a foam cushion,

and a guard extending over said diaphragm and sup-

Claims

1. A headphone having a completely free sound radiation, and including a sound converter with a diaphragm which, with the headphone mounted adjacent a wearer''s ear, is free of loading by the impedance of the ear, said headphone comprising, in combination, a housing; an electro-acoustic converter in said housing having a freely radiating, primarily mass inhibited and damped, diaphragm, with a natural resonant frequency in the range of the lowest sound frequencies; said housing having an opening on one side of said diaphragm for sound transmission from said diaphragm to the entrance to the auditory canal of the wearer''s ear; and rigid supporting means extending from the periphery of said housing opening for supporting said housing at the wearer''s ear, free of engagement with the ear at and around the auditory canal, with the opening of the housing spaced a fixed distance from the wearer''s ear to provide a minimum distance between the diaphragm and the entrance to the auditory canal of the wearer''s ear corresponding to completely contact-free wearing of a sound converter, and defining a large air volume cavity between said diaphragm and the entrance to the auditory canal providing a loose coupling between said electroacoustic converter and the auditory canal; said supporting means defining a plurality of open spaces providing communication between said large air volume cavity and the outside air, and also providing unhindered circulation of ventilating air between the headphone housing and the wearer''s ear; said low frequency resonant diaphragm compensating for the loss of low frequencies resulting from such loose coupling between said electro-acoustic converter and the wearer''s auditory canal due to said supporting means.

3. A headphone, according to claim 1, wherein said supporting means comprise a plurality of individual elements spaced around the periphery of said housing opening, and including a dampening material located adjacent said opening between the diaphragm and the ear and spaced from the ear.

5. A headphone, according to claim 1, wherein said supporting means comprises a radially narrow ring-shaped supporting element engaged around said housing around the opening thereof, said supporting element having a bulging annular edge portion of soft material on its narrow outer edge for fitting against the ear.

8. A headphone, according to claim 6, wherein said sound dampening material comprises a foam cushion, and a guard extending over said diaphragm and supporting said foam cushion.