BLOG #30. The Russian Federation’s Intellectual Property Agency Just Issued a Patent by Mikhail Kucherenko

On June 2nd, 2017 The Russian Intellectual Property Agency issued a patent by Mikhail Kucherenko called “In-the-ear-canal Earphone”:

http://www1.fips.ru/fips_servl/fips_servlet?DB=RUPAT&DocNumber=2621362&TypeFile=html

The patent has entered its PCT phase, which means that we are working now on issuing this patent in other world territories.

Our StereoPravda Spearphone-series' ear monitors are all designed in full accordance with the design principles described in the patent.

The patent’s English translation is below (the corresponding pictures can be seen in the original Russian version of the Patent).

IN-THE-EAR-CANAL EARPHONE

FIELD OF INVENTION

This invention relates to the design of sound-emitting devices, specifically to the design of earphones intended for insertion into the external auditory canal.

PRIOR ART

Earphones intended for insertion into the external auditory canal are usually called intra-aural earphones or earbuds.  Most of them are placed at the entrance of the external auditory canal.  Earphones that are inserted deep into the auditory canal, known as cic (completely-in-canal) earphones, are rare.

A design featuring electroacoustic transducers to be inserted into the external auditory canal is also typical for hearing aids.  Alongside with electroacoustic transducers, these devices may also include microphones. They are intended to solve a medical problem of improving the quality of the sound environment around the user, especially the volume and intelligibility of speech.

Earphones designed primarily for listening to music have a different purpose, and therefore their design is different from that of hearing aids.

An earphone design is known from patent CN201928413, published 10.08.2011, IPC H04R 1/1 0, that comprises two electroacoustic transducers, a low- and high frequency one, arranged in parallel.  When in operation, the transducers are placed at the entrance of the auditory canal.

Another design is described in patent KR101539064, published 23.07.2015, IPC H04R 1/1 0, featuring two electroacoustic transducers mutually aligned off-axis.  Each transducer is preceded by a 3-D chamber that generates echo effects.

A technical solution is known from patent application US20140140565, published 22.05.2014, H04R1 / 10 IPC.  The earphone consists of a shell body, a first electroacoustic transducer with a first acoustic chamber and a second electroacoustic transducer with a second acoustic chamber.  The transducers are arranged off-axis towards each other. The second chamber has an acoustic outlet opening disposed far from the first acoustic chamber.

A solution disclosed in patent US9055366, published 09.06.2015, IPC H 04 R 25/00, is the closest analog to the proposed design.  The earphone described in said patent comprises two electroacoustic transducers, a low- and a high frequency one, arranged in parallel.  The sound emitted by each electroacoustic transducer propagates along its own vector within the casing.  Electroacoustic transducers based on Balanced Armature technology are used in the earphones.

Despite an obvious progress in designing earphones with two electroacoustic transducers, the earphones still need further improvement to enhance their sound quality.

DISCLOSURE OF INVENTION

The technical result of the claimed invention is the improvement of sound quality by enhancing the efficiency of electroacoustic transducers, and reducing nonlinear distortion and longitudinal low-frequency resonance.

The in-the-ear-canal earphone consists of at least three electroacoustic transducers placed in a casing. The casing is intended to be inserted into the external auditory canal until its front end reaches the vicinity of the second bend of the external auditory canal.

The first electroacoustic transducer is installed in the front section of the casing, while all the other electroacoustic transducers are aligned in the casing lengthwise, each having a coaxial acoustic channel with its outlet opening into the front section of the casing. The front section of the casing is drop-shaped and expands at its upper side to fit a typical auditory canal, and bears a flexible ear canal sealing tip.

The in-the ear-canal earphone is inserted deep into the external auditory canal, with the front section of the casing reaching the second bend of the external auditory canal. Such deep positioning of the earphone, while enabling the additional acoustic isolation of the chamber from external noise due to its deep fit, forms a small sealed air chamber between the sealing tip and the eardrum, thus enhancing the efficiency of electroacoustic transducers, which, in its turn, enhances the sound quality.

The reduction of nonlinear distortions and longitudinal low-frequency resonance occurs due to the fact that the air chamber, or ”operational volume”, where the transducers emit sound, is relatively small, and because more than three transducers with coaxial acoustic channels are arranged in the casing lengthwise. Also nonlinear distortions and low frequency resonances are reduced because one transducer is located directly in the front section of the casing, which shifts the resonance to a higher frequency. The coaxial acoustic channels of all other transducers open into the chamber. A parallel propagation of acoustic wave fronts along the co-axial acoustic channels preserves a common wave pattern of all transducers. Being all co-axial, all the transducers perform at their best and their combination displays the best properties.  The presence of a sufficiently large number of electroacoustic transducers - more than three - is important, since their optimal selection allows for the generation of a rich 3-D sound at all frequencies. The location of the earphone, close to a position where the cartilage tissue of the external auditory canal changes into the bone tissue, i.e. near the second bend of the external auditory canal, is important for improving the sound quality.  It enables the transducers to operate within the minimum volume of air in front of the eardrum, thus enhancing their acoustic output. A drop-like shape of the front section of the casing contributes to correct orientation of the earphone in the auditory canal aligning the transducers perpendicular to the surface of the eardrum.

As a rule, electroacoustic transducers are aligned in the casing roughly parallel to each other.

The sound quality is also enhanced because electroacoustic transducers and their acoustic channels are parallel to the general sound propagation vector in the external auditory canal, which is roughly perpendicular to the eardrum.
Each of the transducers can be embodied as an acoustic transducer of a balanced armature-type.

The acoustic axis of the first electroacoustic transducer and the coaxial acoustic channels of the other transducers can be aligned roughly perpendicular to the eardrum during operation. Such an alignment of the first electro-acoustic transducer axis and the axes of acoustic channels of all other transducers emits sound propagation pattern which closely corresponds to the typical sound propagation pattern in an external auditory canal during typical “open ear” hearing process.  

In particular, the flexible sealing tip can be turned upward at an angle of 5 to 20° relative to the casing axis. Such placement of the tip provides a required degree of acoustic isolation of the chamber in front of the eardrum, with the typical geometry of the passage near the second bend of the external auditory canal taken into consideration. At the same time, an acoustic isolation is provided when the earphone is correctly oriented in relation to the typical “general sound propagation vector”. The flexible sealing tip can be made of silicone.

In one embodiment, the electroacoustic transducers are connected in parallel.

BRIEF DESCRIPTION OF DRAWINGS

Fig. 1 shows the location of the in-the-ear-canal earphone in the external auditory canal.
Fig. 2 gives a side view of the in-the-ear-canal earphone design.
Fig. 3 gives an upper view of the in-the-ear-canal earphone design.
Fig.4 gives a front view of an embodiment of the in-the-ear-canal earphone.
Fig. 5 shows a general view of an embodiment of the in-the-ear-canal earphones.

EMBODIMENTS OF THE INVENTION

The in-the-ear-canal earphone (Fig. 2, Fig. 3) comprises a casing 4 holding electroacoustic transducers (speakers). In this example, five transducers 6, 7, 8, 9, 10 with acoustic channels 11, 12, 13, 14 from transducers 7, 8, 9, 10 are used, with their outlets opening into the front section of the casing. The outlet of electroacoustic transducer 6, having no acoustic channel (sound duct), is located directly in the front section of casing 4. In this embodiment, the transducers are represented by transducers of the balanced armature type. They are primarily used for portable hearing aids due to their small size and sound reproduction accuracy. The availability of a significant number of transducers in this design contributes to some sound quality improvement through the selection of different types of transducers of balanced armature-type to achieve a required synergistic effect.

The best version of the earphone design comprises various transducers of balanced armature-type made by some known manufacturers of required components, for example, by Knowles. A combination of different series of transducers, each operating in an optimal mode, produces a rich sound.

Other types of small electroacoustic transducers can be used in the proposed design.
Transducers 6, 7, 8, 9, 10 are arranged in the earphone casing lengthwise in order to streamline and minimize its shape to enable its placement in the external auditory canal.  The outlets of transducers 7, 8, 9, 10 are connected to coaxial acoustic channels 11, 12, 13, 14, whose diameters depend on the frequency response of the tranducer. As seen from Fig. 2 - Fig. 4, the diameters of channels 11 and 14 are larger, because they are connected to low-frequency transducers 7 and 10. The channel diameter is selected based on established patterns; hence, to make frequency distortions introduced by acoustic channels more agreeable to the ear, the channels must have the largest possible diameters and shortest possible lengths. Transducers 6, 7, 8, 9, 10 are electrically interconnected with the resulted resistance of slightly over 2 ohms. The total resistance of a fully assembled earphone measures about 17 ohms and the total value includes the values of resistors connected in series with the driver sections. Said resistors are installed in the earphone connector. Because of their effect upon the frequency response of the finished product, the resistors are selected in the process of general design development.

Electroacoustic transducers 6, 7, 8, 9, 10 can be grouped electrically into separate sections, each of which can be driven by a separate amplifier, thus enhancing the sound quality.

The front section of casing 4 can be shaped as a drop with an expansion on its upper part and a narrowing in the lower one (Fig. 4). Such a shape fits the typical external ear canal best when the earphone is inserted, and provides the latter with optimum orientation by positioning the axes of acoustic channels 11, 12, 13, 14 approximately perpendicular to eardrum 2 (Fig. 1). It is commonly known that the smallest sound distortions, especially at higher frequencies, occur along the axis of transducer emission pattern which is perpendicular to eardrum, including cases when multiple electroacoustic transducers are used.

The front section of casing 4 bears flexible sealing tip 5 (Fig. 2 - Fig. 5). The tip 5 is made of silicone and precedes the front section of casing 4 (Fig. 2, Fig. 3). The tip 5 is turned upward at an angle α (Fig. 2), which is equal to 5 - 20° from the axis of casing 4. Here, the phrase "upward from the axis of casing 4" refers to the earphone position in the external auditory canal. The direction of the external auditory canal is individually variable, but in general, it extends first inward and upward and then turns downward and forward. An upward direction from the casing axis means the orientation of the earphone brought about by the drop-like shape of the front section of casing and the typical anatomical structure of the external auditory canal near the eardrum. Generally, sealing tip 5 has a circular shape (see Fig.4), however, it may be shaped differently to form an isolated chamber in front of eardrum 2.

The in-the-ear canal earphones are inserted into external auditory canal 1 (Fig.1). The front section of casing 4 is located near the second bend of auditory canal 1. The drop-like shape of the casing front section (Fig. 4) and upward turn of a sealing tip 5 by angle α ensure the acoustic isolation of space in front of eardrum 3 and correct orientation of casing 4. The drop-like shape of the front section of casing 4 also makes the insertion of earphones more comfortable. The insertion process is also facilitated by the presence of such a typical anatomical feature as inter-tragal notch running along the entire ear canal.  After its second bend, the auditory canal’s cross section is usually drop-shaped.
It should be noted that this type of earphones is not recommended for certain groups of users. Apart from individual preferences, the earphone usage restrictions are related to external auditory canal diameter and shape.

The proposed earphone design provides the deepest fit in the external auditory canal, while a large number of electroacoustic transducers operate in the minimum acoustic volume in front of the eardrum. At this, one of the transducers has no acoustic channel, while the other transducers have co-axial acoustic channels.

Due to the above mentioned set of design features of the earphone it produces sound characteristics similar to those that typically occur in an open auditory canal, that is when the listener hears the music not "inside the head", but "somewhat outside". The listener has no impression that his/her ears are plugged or that the music plays inside a closed space.

Smaller physical dimensions of the "operational sound volume", defined by the sealing tip 5 and the front section of casing 4, on the one hand, and the eardrum, on the other, reduce the longitudinal low-frequency resonance. A special feature of the proposed design is that its silicone tip 5 does not plug the auditory canal tightly, thus the use of the earphones reduces the resonances’ quality factor to small values compared to when very tight plugging of the ear canal is applied. At the same time, the parallel alignment of electroacoustic transducers and acoustic channels shifts the resulting resonance spectrum of the "sound operational volume" to higher frequencies and mitigates the negative effect of an ear canal “occlusion” upon the audibility of low-frequency resonances.

INDUSTRIAL APPLICABILITY
Featuring minimal parasitic resonances and minimal nonlinear distortions, the proposed earphone design provides the reproduction of high-quality, 3-D, clear and rich sound with flat phase characteristic across the entire audible frequency range, with its sound characteristics being very close to the sound characteristics of the “open ear” response. All the above is supported by the whole set of design features of the earphone. Earphones of the proposed design can be industrially manufactured.

CLAIMS

1. An in-the-ear-canal earphone comprising at least three electroacoustic transducers installed in a casing configured for positioning in the external auditory canal, with the front section of the casing reaching the second bend of the external auditory canal in operational position; wherein the first electroacoustic transducer is installed in the front section of the casing, while all other electroacoustic transducers are aligned along the casing and equipped with coaxial acoustic channels opening into the casing front section, which is shaped like a drop with an expansion on its upper side and bears a flexible sealing tip.

2. The in-the-ear-canal earphone of claim 1, wherein electro-acoustic transducers are aligned in the casing roughly parallel to each other.

3. The in-the-ear-canal earphone of claim 1, wherein each of the electro-acoustic transducers is used as a transducer of a balanced armature-type.

4. The in-the-ear-canal earphone of claim 1, wherein the acoustic axis of the first transducer and said coaxial acoustic channels of all other transducers are oriented in the process of operation roughly perpendicular to the eardrum.

5. The in-the-ear-canal earphone of claim 1, wherein said flexible sealing tip is turned upwards at an angle of 5-20° relative to the casing axis.

6. The in-the-ear-canal earphone of claim 1, wherein said flexible sealing tip is made of silicone.

7. The in-the-ear-canal earphone of claim 1, wherein the electroacoustic transducers are electrically connected in parallel.

ABSTRACT

(54) IN-THE-EAR-CANAL EARPHONE

The invention relates to the design of earphones intended for insertion into the external auditory canal.

The in-the-ear-canal earphone contains at least three electroacoustic transducers arranged in a casing. The casing allows for its insertion into the external auditory canal until its front end reaches the second bend of the external auditory canal. The first electroacoustic transducer is located in the front section of the casing, whereas all other electroacoustic transducers are aligned in the casing lengthwise, and have coaxial acoustic channels opening into the front section of the casing. Bearing a flexible sealing tip, the front section of the casing is drop-shaped and expanded on its upper side to fit a typical human auditory canal.

29.06.2017 // Author:  (Bigmisha) // Number of views:  1575