Abstract
An in-ear headphone device for insertion in an ear canal of a person. The in-ear headphone device comprises a noise microphone, a loudspeaker and a signal processor arranged to provide an active noise control signal on the basis of a recorded audio signal from said noise microphone, wherein said loudspeaker is arranged to reproduce said active noise control signal in said ear canal. Further, the device comprises a damped vent comprising one or more vent elements and one or more dampening elements, said damped vent being arranged to couple said ear canal to an external acoustic environment. The damped vent is characterized by an inward vent transfer function HVI from said external acoustic environment to said ear canal. The damped vent is arranged to dampen an acoustic resonance of said one or more vent elements such that a resonance magnitude of said inward vent transfer function HVI of said damped vent in a resonance frequency range from 100 Hz to 2 kHz is maximally 3 dB greater than a reference magnitude of said inward vent transfer function HVI in a reference frequency range from 20 Hz to 100 Hz.
Claims
1-46. (canceled)
47. An in-ear headphone device for insertion in an ear canal of a person, said in-ear headphone device comprising: a noise microphone, a loudspeaker and a signal processor arranged to provide an active noise control signal on the basis of a recorded audio signal from said noise microphone, wherein said loudspeaker is arranged to reproduce said active noise control signal in said ear canal; and a damped vent comprising one or more vent elements and one or more dampening elements, said damped vent being arranged to couple said ear canal to an external acoustic environment; wherein said damped vent is characterized by an inward vent transfer function H.sub.VI from said external acoustic environment to said ear canal; and wherein said damped vent is arranged to dampen an acoustic resonance of said one or more vent elements such that a resonance magnitude of said inward vent transfer function H.sub.VI of said damped vent in a resonance frequency range from 100 Hz to 2 kHz is maximally 3 dB greater than a reference magnitude of said inward vent transfer function H.sub.VI in a reference frequency range from 20 Hz to 100 Hz.
48. The in-ear headphone device of claim 47, wherein said inward vent transfer function H.sub.VI and said acoustic resonance are properties of said damped vent when said in-ear headphone device is inserted in an ear-canal of said person.
49. The in-ear headphone device of claim 47, wherein said loudspeaker and said damped vent are acoustically separated inside said in-ear headphone device.
50. The in-ear headphone device of claim 49, wherein said loudspeaker and said damped vent are acoustically separated by one or more of a dampening element inside said in-ear headphone device and individual ducts coupling said loudspeaker and said damped vent to said ear canal.
51. The in-ear headphone device of claim 47, wherein said noise microphone is arranged to primarily record sound from one or more of said external acoustic environment and said ear canal.
52. The in-ear headphone device of claim 47, wherein a microphone arranged to primarily record sound from said ear canal is coupled to said ear canal via an individual microphone duct.
53. The in-ear headphone device of claim 47, wherein a microphone is acoustically coupled to said ear canal via said damped vent.
54. The in-ear headphone device of claim 47, wherein said signal processor provides said active noise control signal on the basis of an estimated inward total transfer function H.sub.TI.
55. The in-ear headphone device of claim 54, wherein said estimated inward total transfer function H.sub.TI is based on one or more of an estimation of said inward vent transfer function H.sub.VI, a difference of recordings of sound of said external acoustic environment and said ear canal, respectively, and an estimated outward total transfer function H.sub.TO.
56. The in-ear headphone device of claim 55, wherein said estimated outward total transfer function H.sub.TO is based on a difference of sound reproduced by said loudspeaker and sound recorded by said noise microphone.
57. The in-ear headphone device of claim 47, wherein said signal processor is arranged with an active noise control algorithm to provide said active noise control signal.
58. The in-ear headphone device of claim 47, wherein said estimated inward total transfer function H.sub.TI comprises a time-varying inward transfer function component comprising an inward leak transfer function H.sub.LI, and a static inward transfer function component comprising said inward vent transfer function H.sub.VI.
59. The in-ear headphone device of claim 47, wherein said signal processor is arranged to update a representation of said estimated inward total transfer function H.sub.TI.
60. The in-ear headphone device of claim 47, wherein said signal processer is arranged to provide an active occlusion control signal and said loudspeaker is arranged to reproduce said active occlusion control signal in said ear canal, and wherein said active occlusion control signal is based on a signal recorded from a microphone arranged to primarily record sound from said ear canal.
61. The in-ear headphone device of claim 47, wherein said device further comprises an electroacoustic path comprising a microphone primarily recording environment sound, a variable gain, and said loudspeaker, wherein said electroacoustic path is arranged to couple said external acoustic environment to said ear canal.
62. The in-ear headphone device of claim 61, wherein said electroacoustic path is characterized by an inward electro transfer function H.sub.EI having a high-pass characteristic having a high-pass cut-off frequency.
63. The in-ear headphone device of claim 62, wherein said electroacoustic path is arranged to apply a high-pass gain for frequencies above said high-pass cut-off frequency.
64. The in-ear headphone device of claim 47, wherein said one or more dampening elements comprises one or more selected from the list of a dampening cloth, a dampening net, a dampening foam and dampening slits.
65. The in-ear headphone device of claim 47, wherein said one or more dampening element are characterized by an acoustic impedance, wherein said acoustic impedance is in the range from 20 acoustic ohm to 500 acoustic ohm.
66. An in-ear headphone device set comprising a first in-ear headphone device and a second in-ear headphone device; wherein said first in-ear headphone device is arranged to be fitted into a first outer ear of a user and wherein said second in-ear headphone device is arranged to be fitted into a second outer ear of said user; wherein said first in-ear headphone device and said second in-ear headphone device both comprise: a noise microphone, a loudspeaker and a signal processor arranged to provide an active noise control signal on the basis of a recorded audio signal from said noise microphone, wherein said loudspeaker is arranged to reproduce said active noise control signal in a respective ear canal of said user; and a damped vent comprising one or more vent elements and one or more dampening elements, said damped vent being arranged to couple said ear canal to an external acoustic environment; wherein said damped vent is characterized by an inward vent transfer function H.sub.VI from said external acoustic environment to said ear canal; and wherein said damped vent is arranged to dampen an acoustic resonance of said one or more vent elements such that a resonance magnitude of said inward vent transfer function H.sub.VI of said damped vent in a resonance frequency range from 100 Hz to 2 kHz is maximally 3 dB greater than a reference magnitude of said inward vent transfer function H.sub.VI in a reference frequency range from 20 Hz to 100 Hz.
Description
THE DRAWINGS
[0188] Various embodiments and advantages of the invention will in the following be described with reference to the drawings where
[0189] FIG. 1 illustrates an in-ear headphone device according to an embodiment of the invention,
[0190] FIG. 2 illustrates exemplary inward vent transfer functions according to the invention,
[0191] FIGS. 3a-3c illustrate various in-ear headphone devices according to embodiments of the invention having different microphone layouts,
[0192] FIG. 4 illustrates an in-ear headphone device with a dynamic acoustic leak,
[0193] FIGS. 5a-h illustrate various layouts of the damped vent according to embodiments of the invention,
[0194] FIGS. 6a-6c illustrate the effect of using dampening elements of various acoustical impedances according to some embodiments of the invention,
[0195] FIGS. 7a-7b illustrate one advantageous effect of the damped vent relating to dynamic acoustic leaks, according to preferred embodiments of the invention,
[0196] FIGS. 8a-g illustrate various simulated in-ear headphone devices under the influence of dynamic acoustic leaks relating to inward noise,
[0197] FIGS. 9a-g illustrate various simulated in-ear headphone devices under the influence of dynamic acoustic leaks relating to audio reproduction, and
[0198] FIGS. 10a-c illustrate the influence of user variance in difference scenarios.
DETAILED DESCRIPTION
[0199] FIG. 1 illustrates an in-ear headphone device 101 according to an embodiment of the invention. The illustration of FIG. 1 shows the in-ear headphone device 101 when inserted in an ear canal 110 of a user wearing the device. The in-ear headphone 101 device 101 preferably rests in the outer ear 111 of a user and is provided with a flexible ear tip 112 for providing acoustic sealing in ear canals 110 of different users.
[0200] The in-ear headphone device 101 comprises a damped vent 105 acoustically coupling the ear canal 110 with the external acoustic environment 109 outside from the ear canal 110. Ideally, the in-ear headphone device 101 has an outer shape which blocks the ear canal 110 of the user however small leak paths (not shown in the figure) may naturally occur at the interface between the flexible ear tip 112 and the ear canal 110, and these leaks may change dynamically as the user moves about and for example when the user is talking or chewing.
[0201] The damped vent 105 of this embodiment comprises a vent element 106 which is preferably formed as a circular or half-circular conduit, although other vent element designs are conceivable. The purpose of the damped vent is to facilitate transmissions of acoustic sounds between the external acoustic environment 109 and the ear canal 110, however at reduced sound pressure levels (SPL). The dampening characteristics of the damped vent 105 is provided by the dampening element 107 which in this embodiment is a damping cloth located at one end of the damped vent 105. In another embodiments of the invention, the dampening characteristics of the damped vent 105 is provided by dampening cloth at both ends of the damped vent 105 and in a yet other embodiment of the invention the dampening characteristics of the damped vent 105 is provided by slits or openings in the vent element 106.
[0202] The in-ear headphone device 101 comprises a noise microphone 102 arranged to record primarily acoustic sound from the external acoustic environment 109 and provide a recorded audio signal RAS. In the drawing of this embodiment is shown that the noise microphone 102 is arranged at the external acoustic environment facing end of the in-ear headphone device 101, however in other embodiments of the invention the noise microphone 102 may be arranged further within the in-ear headphone device 101 and be acoustically coupled to the external acoustic environment 109 by a microphone duct (not shown in the figure). The in-ear headphone device 101 further comprises a signal processor 103 configured to receive the recorded audio signal RAS and provide an active noise control signal ANCS on the basis of the received recorded audio signal RAS. A loudspeaker 104 of the in-ear headphone device 101 is arranged to reproduce the provided active noise control signal ANCS in the ear canal 110 of the user of the in-ear headphone device 101. In the drawing of this embodiment is shown that the loudspeaker 104 is contained within the in-ear headphone device 101 and acoustic sound emitted by the loudspeaker is transmitted to the ear canal 110 via a loudspeaker duct 108. However, the loudspeaker duct 108 may, in other embodiments of the invention, be dispensed with and the loudspeaker 104 may be arranged closer to the ear canal facing end of the in-ear headphone device 101. In yet other embodiments of the invention, the loudspeaker duct 108 and the damped vent 105 may be formed as two acoustically divided sub-sections of a combined acoustic port.
[0203] Since the in-ear headphone device 101 according to the invention is arranged to reproduce an active noise control signal it is thus capable of performing a method referred to as active noise control or active noise cancellation. Unwanted sound from the external acoustic environment 109 is recorded by the noise microphone 102 and based on the recorded audio signal RAS the signal processor 104 provides an active noise control signal ANCS which is designed to cancel the unwanted sound within the ear canal 110 of the user by destructive interference when reproduced by the loudspeaker 104.
[0204] FIG. 2 illustrates exemplary inward vent transfer functions H.sub.VI. An inward vent transfer function H.sub.VI may be understood as the transfer function from an external environment to the ear canal, with no substantial influence from dynamic acoustic leaks or the loudspeaker. Three representations of inward vent transfer functions are shown as curves S1-S3. According to the invention, one or more dampening elements are arranged to dampen an acoustic resonance of the inward vent transfer function H.sub.VI.
[0205] The figure displays a reference frequency range 403 from 20 Hz to 100 Hz. Based on the reference frequency range 403, a reference magnitude 400 may be determined, for example as the average sound pressure level of the inward vent transfer functions H.sub.VI in this range. Based on the reference magnitude 400, a resonance magnitude threshold 401 may be determined, for example, the reference magnitude threshold 401 may be 3 dB larger than the reference magnitude 400.
[0206] The curve S1 may be an inward vent transfer functions H.sub.VI of an in-ear headphone device with a vent without substantial damping. Consequently, the curve S1 features a resonance magnitude 405 which exceeds the resonance magnitude threshold 401. A device according to curve S1 may not encompass the advantages of the invention and is not disclosed by the claim.
[0207] The curve S2 may be an inward vent transfer functions H.sub.VI of an in-ear headphone device with a damped vent. The curve S2 features a resonance magnitude 405 which lies within the resonance magnitude threshold 401 according to the invention.
[0208] The curve S3 may be an inward vent transfer functions H.sub.VI of an in-ear headphone device with a damped vent. The resonance magnitude 405 of curve S3 is approximately equal to the reference magnitude 400. The acoustic resonance of the damped vent may for example be approximately critically damped. As such, the resonance magnitude 405 of curve S3 lies within the resonance magnitude threshold 401.
[0209] FIGS. 3a-3c illustrate various in-ear headphone devices 101 according to embodiments of the invention having different microphone layouts.
[0210] FIG. 3a shows the in-ear headphone device 101 of FIG. 1 also when inserted into the ear-canal 110 of a user according to a preferred embodiment of the invention. When in use, the in-ear headphone device 101 is arranged to provide at least a reproduction of an active noise control signal ANCS and this reproduced signal, in the form of acoustic sound waves, combines in the ear canal 110 with sound originating from unwanted sound sources, such as an engine of an airplane or rumbling wheels of a train or bus if the user of the in-ear headphone device 101 is commuting by airplane, train or bus, respectively. Since the active noise control signal ANCS is designed to cancel, e.g. counteract, the unwanted sound, the combined sound, as picked up by the tympanic membrane 201 of the user is effectively perceived as an acoustic null signal.
[0211] With this layout of the noise microphone 102, the noise microphone 102 primarily records sound from the external acoustic environment around the user which indirectly represents unwanted sound as the user will perceive through the headphone device.
[0212] FIG. 3b shows an alternative embodiment of the invention where the noise microphone 102 is arranged in the in-ear headphone device 101 in such a way that it may record sound within the ear canal 110 of the user wearing the in-ear headphone device. With this layout of the noise microphone 102, the noise microphone 102 primarily records sound from within the ear canal of a user, i.e. more or less directly measuring the unwanted sound as the user perceives it.
[0213] FIG. 3c shows yet another alternative embodiment of the invention, where the noise microphone 102 is arranged in a similar way to the noise microphone 102 as shown in the embodiment of FIG. 3b. In this embodiment of the invention, the in-ear headphone device 101 further comprises an auxiliary microphone 202 which is located in the in-ear headphone device 101 similarly to the noise microphone 102 of the embodiment shown in FIG. 3a.
[0214] FIG. 4 shows an in-ear headphone device 101 similar to the in-ear headphone device 101 as shown in the embodiment of FIG. 3a inserted in the ear canal 110 of a user wearing the device. Ideally, the flexible ear tip 112 (not shown in the figure) forms a perfect seal between the in-ear headphone device 101 and the user's ear, however in practice such a perfect seal may not be possible to establish, and small leakages may be present. The figure shows an acoustic leak 203 formed between the in-ear headphone device 101 and the user's ear. The acoustic leak 203 may take on any size and geometry depending on the shape of the user's ear and how the in-ear headphone device 101 is inserted in the ear canal 110. Furthermore, additional leak paths (not shown in the figure) may also be present and these may also take on any size ad geometry. For sake of convenience any arrangement of leakage(s) in the sealing between the in-ear headphone device 101 and the user's ear is referred to as a leak path 203, which may thus be an effective leak path. The acoustic leak 203 may also change dynamically, i.e. over time, as the user moves about, such as when the user is walking or jogging, and also when the user exercises his/her jawbone, such as when the user is speaking.
[0215] The dynamically changing acoustic leak 203 presents an entrance for unwanted sound from the external acoustic environment 109 to enter into the ear canal 110 of the user. As may be understood with reference to FIG. 4, the in-ear headphone device 101 according to any of the previously shown embodiments may also exhibit an acoustic leak 203 when inserted into a user's ear due to e.g. an improper fit of the in-ear headphone device 101.
[0216] In addition to the acoustic leak 203, the damped vent 105 also presents an entrance for unwanted sound from the external acoustic environment 109 to enter into the ear canal 110 of the user. However, unwanted sound from the external acoustic environment 109 which enters through an acoustic leak 203 may exit through the damped vent 105. In this way, the damped vent serves a dual purpose in that sound may enter from the external acoustic environment 109 and into the ear canal 110, and sound passing through an acoustic leak 203 may exit through the damped vent 105 and back into the external acoustic environment 109.
[0217] FIG. 5a-h illustrate various layouts of the damped vent 105 according to embodiments of the invention.
[0218] FIG. 5a shows a sideview of a damped vent 105 according to an embodiment of the invention. The damped vent 105 comprises a vent element 106 in the form of a cylinder and a dampening element 107 in the form of a damping cloth. Although the vent element 106 is illustrated as a cylindrical element in this embodiment, other geometries are also conceivable.
[0219] The dampening element 107 in the form of a damping cloth is illustrated as being located at one end of the vent element 106, however it may be positioned in any end of the vent element 106, and in another embodiment of the invention the damped vent 105 comprises dampening elements 107 in both ends of the damping vent 105. The dampening element 107 of the present embodiment is positioned within an opening of the vent element 106, however, in another embodiment of the invention the dampening element 107 may be positioned in such a way that it covers the opening of the vent element 106.
[0220] FIG. 5b shows a sideview of a damped vent 105 according to an embodiment of the invention. Several vent elements 106 forms a branched damped vent 105 which further comprises a dampening element 107 in the form of a damping cloth. The dampening element 107 of the present embodiment is positioned within an opening of the vent element 106, however, in another embodiment of the invention the dampening element 107 may be positioned in such a way that it covers the opening of the vent element 106. Furthermore, in other embodiments of the invention, the branched damped vent may comprise any number of dampening elements 107, such as dampening elements 107 covering all of the openings of vent elements 106.
[0221] FIG. 5c-5d shows two sideviews of a damped vent 105 according to an embodiment of the invention. FIG. 5c shows a damped vent 105 which is built together with a loudspeaker duct 108, to which the loudspeaker 103 may be acoustically coupled. In this embodiment of the invention, the loudspeaker duct 108 and the damped vent 105 constitutes a cylindrical acoustic tube, i.e. each of the two has a half-cylindrical geometry. In other embodiments of the invention, the loudspeaker duct 108 and the damped vent 105 may constitute a combined acoustic tube having any geometric shape. In FIG. 5c a dashed line c-c is shown which represents a plane c. In FIG. 5d, a view of the embodiment from the plane c is illustrated, showing a longitudinal geometry of the combined loudspeaker duct 108 and damped vent 105.
[0222] FIG. 5e illustrates an embodiment of the invention in which the in-ear headphone device 101 (not shown in the figure) comprises two separate damped vents 105. Each damped vent 105 is similar to the damped vent 101 as shown in relation to the embodiment of FIG. 5a. Likewise, the configuration of damped vents 105 in FIG. 5e comprises vent elements 106 and dampening elements 107. The dampening elements 107 of this embodiment are damping cloth present in openings of the vent elements 106, however other configurations of dampening elements are also conceivable.
[0223] FIG. 5f illustrates an embodiment of the invention in which the damping characteristics of the damped vent 105 is facilitated by dampening elements 107 which takes the form of slits. In another embodiment, dampening elements 107 are integrated into the vent element 106, e.g. to disturb air flow or facilitate air leakage.
[0224] FIG. 5g illustrates an embodiment of the invention, in which a microphone, for example the noise microphone 102, is arranged to primarily record sound from the damped vent 105. The microphone may thus be considered acoustically coupled to a vent element 106 of the damped vent 105 within the in-ear headphone device 101. In other embodiments, the in-ear headphone device 101 comprise several vent elements 106, and a microphone and/or a loudspeaker may be coupled to any of these vent elements 106 according to embodiments of the invention. In the embodiment shown in FIG. 5g, the damped vent 105 has a single dampening element 107 at one side. In such embodiments, the microphone may thus primarily record sound from an external environment, or primarily record sound from the ear canal, depending on the exact positioning of the dampening element 107 and the microphone.
[0225] FIG. 5h illustrates an embodiment of the invention in which a loudspeaker duct 108 and the damped vent are partially coupled by a dampening element 107. The damped vent 105 also further comprise dampening elements 107 at both ends of a vent element 106. The loudspeaker duct 108 and the damped vent 105 may feature any type of partitioning according to embodiments of the inventions. The loudspeaker 103 may for example be acoustically coupled to the damped vent 105 within the in-ear headphone device 101, be acoustically decoupled with the damped vent 105 within the in-ear headphone device 101 (see e.g. FIG. 5c), or be partially coupled with the damped vent 105 within the in-ear headphone device 101, as illustrated in FIG. 5h.
[0226] In the above descried embodiments of the invention, various configurations of damped vents 105 are demonstrated. However, the invention is not restricted to any specific configuration and various other embodiments are thus available to a skilled person. The damped vent configuration may be realized by any combination of the above described embodiments; thus, the damped vent configuration may comprise one or more damped vents 105, individual damped vents may comprise any number of vent elements 106 and dampening elements 107, microphones and/or loudspeaker may be acoustically coupled to vent elements or may have individual ducts, and vent and ducts may have any geometric shape.
[0227] FIGS. 6a-6c illustrate the effect of using dampening elements of various acoustical impedances according to some embodiments of the invention, compared to an open ear. The presented data has been obtained by performing a simulation of the system, using an equivalent electronics diagram as illustrated in FIG. 6a which may be replicated by a person skilled in the art.
[0228] The simulation shown in FIG. 6a corresponds to a typical embodiment of the invention. A 60 dB signal simulation source 300 corresponds to noise from an external environment, and the top ear simulation microphone 301 corresponds to sound heard in the ear. In this simulation, sound may enter the ear canal via two different paths: a vent diagram path 302 and a leak diagram path 304. The vent diagram path 302 is portioned such that the first part of the vent diagram path consists of two vent elements, which merge to a single vent element. The leak diagram path 304 has a large acoustic impedance in this specific simulation, corresponding to no substantial dynamic acoustic leak.
[0229] The vent diagram path 302 comprise an impedance R.sub.V, corresponding to a dampening element according to the invention. For the FIGS. 6b-6c, the value of this impedance is varied, to simulate the effect of using dampening elements of different acoustical impedances.
[0230] In FIG. 6b, the simulated curve S4 shows a signal corresponding to an open ear. The curve has a characteristic resonance at approximately 3 kHz.
[0231] The simulated curves S5-S9 correspond to acoustical impedances R.sub.V of 0 acoustical ohm, 45 acoustical ohm, 90 acoustical ohm, 180 acoustical ohm, and 360 acoustical ohm, respectively, where all the provided values are acoustical ohm in CGS units. As evident from the simulations, a resonance is clearly present at approximately 900 Hz when the acoustical impedance is low. However, as the acoustical impedance is increased, the resonance is damped, and for a sufficiently large acoustical impedance, no resonance peak feature is visible. If a very large acoustical impedance is chosen, a broad range of frequencies are damped, and not only the resonance. As such, for this simulated embodiment, a preferable acoustical impedance is approximately 180 acoustical ohms, since the resonance feature has been removed, but besides this, sound below the desired cut-off frequency has not been substantially damped.
[0232] For different embodiments of the invention, the preferred acoustical impedance of a dampening element may vary. The acoustical impedance may for example depend on the composition of vent elements, the cross-sectional area of vent elements, the length of vent elements, and the remaining volume of the ear canal, when the device is inserted. The primary aim of the dampening element is typically to remove a Helmholtz resonance feature, without damping additional sound unnecessarily, and the acoustical impedance should thus be chosen accordingly.
[0233] Some embodiments of the invention may also comprise several dampening elements, and preferably, their combined effect should be to suppress a Helmholtz resonance, which would occur without dampening elements, when the device is inserted.
[0234] FIG. 6b additionally shows how a damped vent may decrease the sound pressure in the ear at frequencies above a desired cut-off. Compared to the open ear, the attenuation may reach 20 dB or more in the region of the open ear canal resonance. At higher frequencies resonances—that may vary significantly from ear to ear—can also be attenuated by the damped vent in combination with other acoustical elements such as a damped entrance to a cavity, such as a loudspeaker front volume. In the exemplary illustration of the figure, the difference in magnitude of sound pressure level between the peak values of the two resonance features of curves S5-S9 and curve S4 at approximately 8 kHz and approximately 9 kHz, respectively, is 9 dB. This dampening effect at relatively high frequencies may be preferential in some embodiments of the invention.
[0235] FIG. 6c illustrates the same curves as in FIG. 6b, but now shown relative the simulation curve relating to an open ear S4. The curves shown in FIG. 6c may thus be interpreted as passive insertion gains, i.e. the change in gain experienced by a user when an inactive device is worn. Note that the simulation data has been truncated at approximately 6.5 kHz for simplicity. The insertion gain data in this frequency region is visually affected by the resonance features at 8 kHz-9 kHz shown in FIG. 6b, but the detailed variations in these features do not significantly affect the overall perception of sound under normal conditions with common signals.
[0236] FIGS. 7a-7b illustrate one advantageous effect of the damped vent 105, according to preferred embodiments of the invention. The presented data has been obtained by performing a simulation of the system, using an equivalent electronics diagram as illustrated in FIG. 7a which may be replicated by a person skilled in the art.
[0237] The simulation shown in the top part of FIG. 7a corresponds to a typical embodiment of the invention with a damped vent, whereas the bottom part corresponds to an in-ear headphone device without a damped vent. A 60 dB SPL signal simulation source 300 corresponds to noise at the entrance to the concha from an external environment, and the ear simulation microphones 301 correspond to sound heard in the ear for the two simulated devices. In simulations of typical embodiments of the invention, the signal may enter the ear canal via three different paths: a vent diagram path 302, an electroacoustic diagram path 303, and a leak diagram path 304. However, in the simulation shown in FIG. 7a-b, the signal simulation source 300 is only connected to the ear simulation microphone 301 via the leak diagram path 304. As such, this simulation relates to sound entering the ear through dynamic acoustic leaks. A signal which has entered through the leak diagram path 304 may exit through the vent diagram path 302, and the signal recorded by the ear simulation microphone 301 is therefore decreased.
[0238] The leak diagram paths 304 of both simulated devices of FIG. 7a both comprise a diagram element which has a leak diameter Dlk/DLK, corresponding to the diameter of a dynamic acoustic leak. In each figure, this leak diameter is varied to display the influence that a dynamic acoustic leak may exert on the signal reaching the ear simulation microphone 301.
[0239] FIG. 7b illustrates the signals reaching the ear simulation microphones, where curves S16-S20 correspond to the simulated in-ear headphone device with a damped vent, and curves S21-S25 correspond to the simulated device without a damped vent. The curves S16-S20 and S21-S25 correspond to leaks with a combined cross-sectional area equivalent to a circular cross-section with diameter of 0.035 cm, 0.05 cm, 0.07 cm, 0.08 cm, and 0.1 cm, respectively.
[0240] For the simulated curves S21-S25, any signal which has entered the region of the ear simulation microphone 301, will tend to stay at the ear simulation microphone 301, and a large signal will thus be recorded. In contrast, for the simulated curves S16-S25, the sound pressure level recorded by ear simulation microphone 301 is remarkably lower, since a signal in the region of the ear simulation microphone 301 may leave this region through the vent diagram path 302. For example, for a leak diameter of 0.05 cm, the difference in the leak-contributed sound pressure level at 200 Hz is approximately 12 dB between the simulated devices as displayed by curves S17 and S22.
[0241] The simulation and its results as illustrated in FIG. 7a-b therefore serve as evidence that embodiments of the invention may reduce the influence of dynamic acoustic leaks in the ear canal by allowing sound to exit through the damped vent.
[0242] FIGS. 8a-g illustrate various simulated in-ear headphone devices under the influence of dynamic acoustic leaks, the devices having either no vent, an open undamped vent, or having a damped vent.
[0243] The presented data has been obtained by performing a simulation of the system, using an equivalent electronics diagram as illustrated in FIG. 8a which may be replicated by a person skilled in the art.
[0244] The simulation diagram shown in FIG. 8a corresponds to an in-ear headphone device. A 60 dB SPL constant-pressure signal simulation source 300 corresponds to noise at the entrance of the concha from an external environment, and an ear simulation microphone 301 corresponds to sound heard in the ear. A signal may reach the ear simulation microphone 301 via three different paths: a vent diagram path 302, an electroacoustic diagram path 303, and a leak diagram path 304. However, in the simulations relating to FIGS. 8a-g, the electroacoustic diagram path 303 does not carry a signal.
[0245] The vent diagram path 302 is portioned such that the first part of the vent diagram path consists of two vent elements, which merge to a single vent element, where an impedance R.sub.V is located. For the various figures FIGS. 8b-8c, FIGS. 8d-8e, and FIGS. 8f-8g, the value of the impedance is varied to simulate a device with no vent (large impedance), a device with an open, undamped vent (small impedance), and a damped vent (intermediate impedance), respectively.
[0246] The leak diagram path 304 has a leak diameter Dlk/DLK, corresponding to the equivalent diameter of a dynamic acoustic leak. In each figure, this leak diameter is varied to display the influence that a dynamic acoustic leak may exert on the signal reaching the ear simulation microphone 301.
[0247] FIGS. 8b-8c illustrate the signal reaching the ear simulation microphone 301 for a device with no vent, i.e. R.sub.V=1 megaohm (acoustical) in CGS units, where FIG. 8b shows the sound pressure level magnitude of the transferred signal, and FIG. 8c shows the phase of the transferred signal. Both these entities are relevant for active noise control. The curves S26-S28 and S29-S31 correspond to leak diameters of 0.05 cm, 0.07 cm, and 0.1 cm, respectively.
[0248] FIG. 8b clearly illustrates how dynamical leaks may influence the signal magnitude, e.g. influence the magnitude of the inward total transfer function H.sub.TI. Particularly in the range from 400 Hz and upward, the difference in sound pressure level is 10 dB to 15 dB.
[0249] Furthermore, FIG. 8c illustrates how dynamical leaks may additionally influence the signal phase, particularly in the range from 100 Hz to 700 Hz.
[0250] As such, these simulations illustrate the enormous effect that dynamic acoustic leaks may have for an in-ear headphone device with no vent.
[0251] FIGS. 8d-8e illustrate the signal reaching the ear simulation microphone 301 for a device with an open undamped vent, i.e. R.sub.V=0, where FIG. 8d shows the sound pressure level magnitude of the transferred signal, and FIG. 8e shows the phase of the transferred signal. Both these entities are relevant for active noise control. The curves S32-S35 and S36-S39 correspond to leak diameters of 0 cm, 0.05 cm, 0.07 cm, and 0.1 cm, respectively.
[0252] FIG. 8d shows how an in-ear headphone device with an open vent may suffer from the presence of a Helmholtz resonance. The addition of a dynamic acoustical leak may shift the location of this resonance to a different frequency, which can be problematic to continuously handle for a device arranged to provide active noise control.
[0253] FIG. 8e illustrates the signal phase in a device with an undamped vent, and how dynamic acoustic leaks influence the signal phase. Below 500 Hz, the phase is relatively well behaved, regardless of any dynamic acoustic leaks. However, approaching 1 kHz from below, the phase has a sharp downwards trend. Generally, this sharp transition is disadvantageous for active noise control purposes. Dynamic acoustical leaks may shift this sharp transition around, which further problematizes this phase behavior.
[0254] As such, these simulations illustrate how a device with an undamped vent may have severe problems in providing optimal active noise control.
[0255] FIGS. 8f-8g illustrate the signal reaching the ear simulation microphone 301 for a device with a damped vent, i.e. R.sub.V=180 acoustical ohm in CGS units, where FIG. 8f shows the sound pressure level magnitude of the transferred signal, and FIG. 8g shows the phase of the transferred signal. Both these entities are relevant for active noise control. The curves S40-S43 and S44-S47 correspond to leak diameters of 0 cm, 0.05 cm, 0.07 cm, and 0.1 cm, respectively.
[0256] FIG. 8f illustrates how dynamical leaks may influence the signal magnitude. In comparison with simulations for a device with no vent (FIG. 8b-8c), the influence of the leaks is significantly smaller. For example, at 1 kHz, the difference in sound pressure level between a leak diameter of 0.05 cm and 0.1 cm is approximately 3 dB with a damped vent, whereas this difference is approximately 15 dB with no vent. In comparison with simulations with an undamped vent (FIG. 8d-8e), the simulations with a damped vent display no Helmholtz resonance. A resonance-like feature does arise for larger leaks, but this feature is more well behaved than the Helmholtz resonance shown in FIG. 8d, which shifts frequency as the leak size is changed.
[0257] FIG. 8g illustrates the signal phase in a device with a damped vent, and how dynamic acoustic leaks influence this signal phase. Across the entire range relevant for active noise control, i.e. frequencies up to approximately 1 kHz, the phase is well behaved for any of the simulated dynamic acoustic leaks.
[0258] The simulations of FIGS. 8a-8g are thus evidence that, in the context of dynamic acoustic leaks, an in-ear headphone device with a damped vent is superior for active noise control purposes, compared to devices without a vent and with an undamped vent. Particularly, it has been shown that variations due to dynamic acoustic leaks influencing the magnitude of the inward total transfer function H.sub.TI may be reduced and distortion due to dynamic acoustic leaks influencing the phase of the inward total transfer function H.sub.TI may be reduced. These improvements may be obtained by the control and dampening of the Helmholtz resonance established by the ear canal and an acoustical path to the environment.
[0259] FIGS. 9a-g illustrate various simulated in-ear headphone devices under the influence of dynamic acoustic leaks, the devices having either no vent, an open undamped vent, or having a damped vent. Particularly, an electroacoustic diagram path comprises a simulated loudspeaker generating a signal, which is transmitted to an ear simulation microphone 301.
[0260] The presented data has been obtained by performing a simulation of the system, using an equivalent electronics diagram as illustrated in FIG. 9a which may be replicated by a person skilled in the art.
[0261] The simulation diagram shown in FIG. 9a corresponds to an in-ear headphone device. For the purpose of illustration, a simple loudspeaker model consisting of a constant volume velocity source and a front volume is established. The simulated loudspeaker delivers the signal to the ear canal through diagram path 303. The amplitude of the constant volume velocity source is adjusted to yield a signal of approximately 60 dB SPL at low frequencies in the ear simulation microphone. The behavior of this signal at the ear simulation microphone 301 is of relevance to active noise control and reproduction of a desired audio signal. The signal may typically partially reach the ear simulation microphone 301, and partially exit the simulated ear canal region through a vent diagram path 302, and a leak diagram path 304.
[0262] The vent diagram path 302 is portioned such that the first part of the vent diagram path consists of two vent elements, which merge to a single vent element, where an impedance R.sub.V is located. For the various figures FIG. 9b-9c, FIG. 9d-9e, and FIG. 9f-9g, the value of the impedance is varied to simulate a device with no vent (large impedance), a device with an open, undamped vent (small impedance), and a damped vent (intermediate impedance), respectively.
[0263] The leak diagram path 304 has a leak diameter Dlk/DLK, corresponding to the cross-section of a dynamic acoustic leak. In each figure, this leak diameter is varied to display the influence that a dynamic acoustic leak may exert on the signal reaching the ear simulation microphone 301.
[0264] FIGS. 9b-9c illustrate the signal reaching the ear simulation microphone 301 for a device with no vent, i.e. R.sub.V=1 megaohm (acoustical) in CGS units, where FIG. 9b shows the sound pressure level magnitude of the signal, and FIG. 9c shows the sound pressure level magnitude of the signal relative to a reference signal with no dynamic acoustic leak. The curves S48-S53 and S54-S59 correspond to leak diameters of 0 cm, 0.03 cm, 0.05 cm, 0.07 cm, 0.08 cm, and 0.1 cm, respectively.
[0265] FIGS. 9b-9c clearly illustrate how dynamical leaks may influence the magnitude of a signal from a loudspeaker reaching the ear in an in-ear device with no vent relating to the transfer function from loudspeaker to the ear drum, also relating to the outwards total transfer function H.sub.TO. Particularly at low frequencies, the influence of leaks is enormous, e.g. at 150 Hz, the difference in sound pressure level between the shown curves is more than 25 dB. Furthermore, this difference in sound pressure level is significant up to more than 1 kHz.
[0266] As such, these simulations illustrate the massive influence that dynamic acoustic leaks may have for an in-ear headphone device with no vent.
[0267] FIGS. 9d-9e illustrate the signal reaching the ear simulation microphone 301 for a device with an open undamped vent, i.e. R.sub.V=0, where FIG. 9b shows the sound pressure level magnitude of the signal, and FIG. 9c shows the sound pressure level magnitude of the signal relative to a reference signal with no dynamic acoustic leak. The curves S60-S64 and S65-S69 correspond to leak diameters of 0 cm, 0.03 cm, 0.05 cm, 0.07 cm, and 0.1 cm, respectively.
[0268] FIG. 9d clearly illustrate how an in-ear headphone device with an open, undamped vent may suffer from extensive loss of sound, relating to the impedance of the outward sound path. Particularly in the bass frequency regime, the signal recorded by the ear simulation microphone 301 is 20 dB-30 dB lower than the signal of 60 dB emitted from the simulated loudspeaker.
[0269] These simulations thus show that a device with an undamped vent is ill-suited for audio reproduction.
[0270] FIGS. 9f-9g illustrate the signal reaching the ear simulation microphone 301 for a device with a damped vent, i.e. R.sub.V=180 acoustical ohm in CGS units, where FIG. 9f shows the sound pressure level magnitude of the signal, and FIG. 9g shows the sound pressure level magnitude of the signal relative to a reference signal with no dynamic acoustic leak. The curves S70-S75 and S76-S80 correspond to leak diameters of 0 cm, 0.03 cm, 0.05 cm, 0.07 cm, 0.08 cm, and 0.1 cm, respectively.
[0271] The simulation curves of FIGS. 9f-9g show a large reduction of difference in magnitude between the curves of different simulated leak diameters in comparison with FIGS. 9b-9c. Furthermore, a comparison between FIG. 9d and FIG. 9f shows that a device with a damped vent do not suffer from extensive loss of sound in the bass frequency regime.
[0272] The simulations of FIGS. 9a-9g are thus evidence that, in the context of dynamic acoustic leaks, an in-ear headphone device with a damped vent is superior for active noise control purposes and sound reproduction, compared to devices without a vent and with an undamped vent. An in-ear headphone device with a damped vent may provide an advantageous balance between a low magnitude of the outward total transfer function H.sub.TO and variations of the outward total transfer function H.sub.TO due to dynamic acoustic leaks, especially at low frequencies. As such, it has been shown that distortion due the influence of dynamic acoustic leaks on the outward total transfer function H.sub.TO affecting loudspeaker feedback and active noise control may be reduced, and at the same time limiting the reduction in sound pressure from the loudspeaker at the ear drum due to sound exiting via the vent.
[0273] FIGS. 10a-10c illustrate the influence of user variance, e.g. different ear canal sizes between users and different insertion positions, in difference scenarios: an open ear, an in-the-canal device with an open vent, and an in-ear headphone device with a damped vent.
[0274] The simulation diagram shown in FIG. 10a corresponds to (from top to bottom) an in-ear headphone device with a damped vent, an in-the canal device, an open ear, and a reference open ear. A 60 dB signal simulation source 300 corresponds to noise from an external environment, and the various ear simulation microphones 301 corresponds to sound heard in the ear in the difference scenarios.
[0275] Before ear simulation microphones 301, a diagram element is located, which simulates an ear canal. In the simulations, the simulated ear canal depends on a parameter vLcnl/CLCNL, corresponding to the size of a portion of the ear canal, and this parameter is varied, to study the influence of user variance. The diagram element after the reference open ear diagram path 307 simulating an ear canal is not varied and the simulated signal recorded by the corresponding ear simulation microphone is used for reference.
[0276] FIG. 10b illustrates the signals reaching the various ear simulation microphones, where curves S81-S83 correspond to the simulated in-ear headphone device with a damped vent, curves S84-S86 correspond to the simulated in-the-canal device, and curves S87-S89 correspond to the open ear. The simulated size of the portion of the ear canal is −0.2 cm, 0 cm, and 0.2 cm within each scenario.
[0277] Generally, above 6 kHz-7 kHz, all the curves are dominated by sharp resonance features. These features are typical for ears at these frequencies. Inserting an in-ear headphone device may change alter these features, but the resonant behavior will typically persist in some form.
[0278] Additionally, the open ear curves S87-S89 all display a well-known natural resonance of the ear at approximately 3 kHz, and the in-the canal curves S84-S86, display a Helmholtz resonance at approximately 1 kHz. In contrast, the damped vent curves S81-S83 show no resonance features below 6 kHz-7 kHz.
[0279] Active noise control is typically implemented at frequencies up to 1 kHz. In this range, it is primarily the in-the canal curves S84-S86 which are influenced by user variance. In contrast, the damped vent curves S81-S83 are minimally influenced.
[0280] FIG. 10c illustrates the same curves as in FIG. 10b, but now shown relative to a curve obtained by a reference open ear diagram path 307. The curves shown in FIG. 10c may thus be interpreted as passive insertion gains, i.e. the change in gain experienced by a user when an inactive device is worn.
[0281] The simulations of FIGS. 10a-10c are evidence that, in context of user variance, an in-ear headphone device with a damped vent is an improvement compared to an in-the-canal device with an open vent. Particularly, the simulations show distortion due to user variance influencing the magnitude of the inward total transfer function H.sub.TI may be reduced, according to embodiments of the invention.
LIST OF REFERENCE SIGNS
[0282] 101 In-ear headphone device [0283] 102 Noise microphone [0284] 103 Signal processor [0285] 104 Loudspeaker [0286] 105 Damped vent [0287] 106 Vent element [0288] 107 Dampening element [0289] 108 Loudspeaker duct [0290] 109 External acoustic environment [0291] 110 Ear canal [0292] 111 Pinna (outer ear) [0293] 112 Flexible ear tip [0294] 201 Tympanic membrane (ear drum) [0295] 202 Auxiliary microphone [0296] 203 Acoustic leak [0297] 300 Signal simulation source [0298] 301 Ear simulation microphone [0299] 302 Vent diagram path [0300] 303 Electroacoustic diagram path [0301] 304 Leak diagram path [0302] 305 Open ear diagram path [0303] 306 In-the-canal diagram path [0304] 307 Reference open ear diagram path [0305] 400 Reference magnitude [0306] 401 Resonance magnitude threshold [0307] 402 Magnitude threshold distance [0308] 403 Reference frequency range [0309] 404 Resonance frequency range [0310] 405 Resonance magnitude [0311] S1-S97 Simulation signal curves [0312] RAS Recorded audio signal [0313] ANCS Active noise control signal [0314] H.sub.VI, H.sub.VO Inward vent transfer function, Outward vent transfer function [0315] H.sub.LI, H.sub.LO Inward leak transfer function, Outward leak transfer function [0316] H.sub.TI, H.sub.TO Inward total transfer function, Outward total transfer function [0317] H.sub.EI Inward electro-acoustic transfer function
