Patent Translate Powered by EPO and Google Notice This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate, complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or financial decisions, should not be based on machine-translation output. DESCRIPTION JP2006121709 An overhead microphone assembly has a plurality of unidirectional microphone elements. The microphone assembly is overhead and generally located above the desired sound source and below the undesired sound source. The signals from the plurality of microphone elements are provided to a microphone steering processor that can mix and gate the signals to ensure the best signal to noise ratio. The microphone steering processor is also capable of dynamically tracking the source if tracking (source localization) is desired. The resulting acoustic signal from the microphone steering processor can be further subjected to processing such as echo cancellation, noise cancellation and acoustic gain control. [Selected figure] Figure 2 Ceiling microphone assembly [0001] The present invention generally relates to a microphone assembly in a system required to convert an audio signal into an electrical signal. [0002] A microphone is a basic and essential element in any acoustic system. There are many types of microphones currently used. In general, those microphones fall into four categories as listed in FIG. The first category is omnidirectional microphone 102. It has uniform polar response, ie it can accept sound waves from any direction, and an electrical signal is 04-05-2019 1 generated with the same gain. The second type of microphone is a dipole microphone 104, which can respond to sound waves from mainly two opposite directions. Sound waves coming from other directions have very little gain. Sound waves coming from directions that are 90 ° to the axis of the microphone element are not accepted, ie the gain is zero. The third type of microphone is a cardioid microphone 106, which can receive sound waves from one primary direction. The response gain decreases as the incident angle of the sound wave deviates from the primary direction. The response gain drop becomes larger when the incident angle is larger than the threshold. The gain is zero at 180 ° from the primary direction. The fourth type of microphone is a hypercardioid microphone 108. The high parkar geoid microphone 108 is like a hybrid of a dipole microphone and a cardioid microphone. It has a primary direction and a secondary direction, the secondary direction being the opposite direction of the primary direction. It can respond to sound waves that are in both the primary and secondary directions, but the gain for the secondary direction is less than the gain for the primary direction. [0003] It is possible to assemble an array of microphones to compete for the above four microphone characteristics in an application. For example, non-directional microphones can be grouped together. The controller can process the signal in such a way as to generate a signal that is very directional, and thus the array of such microphones functions as if it were a directional microphone Do. Another example is described in US Pat. No. 5,715,319, in which several directional microphones are arranged in a circular array. The resulting microphone array functions like an omnidirectional or omnidirectional microphone. In this application, the microphone elements are referred to as general single element microphones or multi-element arrays that behave like a single element microphone. For example, a unidirectional microphone is a single cardioid microphone or microphone array that receives sound waves from the primary direction and does not receive sound waves from most other directions. The microphone elements in the microphone array can be non-directional, bipolar or hypercardioid or a combination. [0004] Any one of the four types of microphones identified above is an audio system and has various disadvantages, particularly in video conferencing and audio conferencing applications. For example, omnidirectional microphones that collect speech equally from all directions have lower noise and echo levels because they can not accept echoes and noise under typical unprocessed room conditions Are of poor quality in audio or video conferencing applications. A cardioid 04-05-2019 2 microphone only accepts sound waves directed towards it and does not accept most sound waves coming from other directions. This type of microphone can provide greater signal-to-noise ratio (SNR) and higher voice quality, but covers only a very small area in a conference room. Participants in a voice or video conference need to speak to the microphone in turn. In some conference room settings, several such microphones are connected to the system at the same time, so most participants in the conference use nearby microphones available to speak Can. [0005] It is generally accepted that a person must have a microphone during a lecture in a large hall, but it is still unnatural and inconvenient. Under the circumstances of the meeting, it is not preferable. In an actual meeting, the conference participants prefer to look at the facial expressions and other body language of the participants while they are speaking. [0006] Prior art devices exist to avoid the many limitations of microphone elements. For example, the Polycom SoundStation VTX-1000 speakerphone by the applicant of the present invention uses three microphone elements to provide good room coverage, SNR and frequency response. Such speakerphones can meet many requirements in setting up a conference room as seen on most conference room tables. [0007] There is a great demand to eliminate inconvenient microphones, or at least to get out of view during a meeting and to minimize their interference. It is desirable to have a microphone system that can cover the entire conference room while at the same time maintaining high voice quality and minimizing signal to noise ratio. There is a need to have a microphone system that can provide other high quality speech processing. [0008] In the present invention, multiple unidirectional microphone elements are used in the 04-05-2019 3 microphone assembly. As a microphone assembly, in general, the preferred sound source is placed overhead. The signals from the plurality of microphone elements are provided to a microphone steering processor that mixes and gates the signals to ensure the best signal to noise ratio. The stealing processor also performs dynamic tracking of the audio source when such tracking (audio source positioning) is desired. The acoustic signal obtained from the steering processor can be further processed such as echo cancellation, noise reduction and automatic gain control. The microphone of the present invention can cover a large conference room. The microphones can also be scaled, i.e., as the conference room gets larger, the capabilities of the microphones can be appropriately enhanced by adding more microphones. [0009] BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of the present invention, reference will now be made in detail to the preferred embodiments with reference to the accompanying drawings. [0010] FIG. 2 shows a typical meeting room arrangement 244. The meeting participants 210 are seated at the meeting room table 222 and are facing the video monitor 252 on the wall 242. A microphone 202 (or several microphone elements in a speaker book such as a Polycom SoundStation VTX-1000 speakerphone) can be placed on the conference room table 222. Utterances 232 propagate through the conference room and are reflected by walls, eg 242 and ceiling 240. Reflected sound waves, also referred to as room echoes, are generally undesirable and, if necessary, not acceptable to the microphone. It can be done when a cardioid microphone is used. The cardioid microphone only receives sound waves in one direction. Reflected sound waves in the opposite direction are not accepted. Thus, the cardioid microphone does not accept the first stage echoes from the unwanted room, leading to an improved echo ratio over the direct case. [0011] According to embodiments of the present invention, the single-cardioid microphone element can only accept sound waves in a small area along the primary direction, so that the microphone can accept speech from many directions as required As can be done, several microphone elements 04-05-2019 4 are provided at the microphone. FIGS. 3 (a) to 3 (c) illustrate the audio response coverage of a microphone having three cardioid microphone elements. The cardioid microphone element is connected to a microphone steering controller (eg, shown in FIG. 9) that controls and processes signals generated by the cardioid microphone element. In this embodiment, there are three elements 302, 304 and 306, each spaced 120 degrees apart. The corresponding response coverage is shown in FIGS. 3 (a) to 3 (c). The microphone steering controller selects the best microphone element by detecting the best speech quality among those three elements. In FIG. 3 (a), when the participant 310 speaks, the microphone element 302 with the response 312 is activated. The other microphone elements 304 and 306 are disabled and ignored by the microphone steering controller. Similarly, when participant 320 speaks, only microphone element 304 is activated to respond 314. When participant 330 speaks, only microphone element 306 is activated to respond 314. In FIGS. 3 (a) to 3 (c), while speakers 310, 320 and 330 are shown as three different people, they can only move one of three different locations within the conference room. It can be a person, or some combination of them. [0012] When more than one person speaks, more than one microphone element can be selected. The microphone steering controller is designed to intelligently distinguish between human speech and other noise, such as air conditioner noise, so that the controller is "not fooled" by the noise. This ensures that the best acoustic quality is always maintained as the speaker (or the instructor in the long distance education application) roams the room where the air conditioner is installed. The tracking speed of the controller is virtually instantaneous, since it has no mechanical moving parts. The microphone steering controller readily determines which microphone element has been selected, and the signal is further processed by the controller or other downstream processor, as required. The microphone steering controller can also perform gating and mixing to combine signals from two or more microphone elements to generate an output microphone signal. [0013] The microphones according to the above embodiment are shown to be much better than existing commercially available microphones. FIG. 4 shows contours of speech quality. A commercially available omnidirectional microphone is used as a reference. The distance for omnidirectionality to produce a very good sound is about 8 feet, as shown by contour line 414. Contour lines 412 for the above embodiment of the present invention are also shown. Contour line 4112 is approximately 14 feet from the microphone and covers an area of approximately 600 square 04-05-2019 5 feet. [0014] 5 to 7 show further characteristics of the microphone of the above embodiment. FIG. 5 shows a frequency response curve 510 in the direction of the microphone element. FIG. 6 further illustrates the frequency response for different angles of incidence. The microphone has three identical cardioid microphone elements located at 120 ° apart, which are symmetrical so that only one cardioid microphone element at 0 ° to + 60 ° It is sufficient to check the performance only. The performance curve at -60 ° to 0 ° is symmetrical to the performance curve at 0 ° to + 60 °. As shown in FIG. 6, the frequency responses for all incident angles in the range of 0 ° to 60 ° almost overlap each other and show a very uniform angular response. This means that where the speaker walks in the room around the microphone, the tonality remains the same. Because of the uniform response across different angles of incidence, single frequency equalizers can flatten their frequency response, even though the frequency response is not flat. [0015] FIG. 7 shows very detailed polar responses for various frequencies in the range of 250 Hz to 3500 Hz. While their plots (702-714) show wide-angle sound collection, the average before and after rejection is very good, keeping at 20 dB at 1000 Hz and 15 dB at 3500 Hz. [0016] In the above embodiment, one microphone has three cardioid microphone elements. The number of cardioid microphone elements may be more or less based on the characteristics of those cardioid microphone elements and the needs of a particular application. In particular, when the conference room or the lecture hall is larger than 600 square feet provided by a single microphone as described above, install additional microphones in cooperation with each other under the control of the microphone steering controller be able to. In one embodiment, three microphones are installed in the lecture hall. The total coverage is 1800 square feet, which is a huge conference room that can seat about 150 people comfortably. [0017] 04-05-2019 6 Figures 8 (a) and 8 (b) show a typical conference room according to an embodiment of the invention, using two microphones as described above. FIG. 8 (a) is a plan view, and FIG. 8 (b) is a side view. The conference room is equipped with a video monitor 8101 and a video camera 8105 at one end of the conference room. The conference table 8119 is located at the center of the conference room. Microphones 8110 and 8120 are overhead microphones. The microphones are maintained above the conference participants. In this conference room, there are no other objects between the overhead microphone and the conference participants. The microphone elements in the overhead microphone can receive sound waves directly from the conference participants. In one embodiment, the overhead microphone is suspended from the ceiling above the conference participants. In this way, there are no microphones, associated wires or other components placed around the conference table that would interfere with the conference participants. Further details regarding the assembly are described below with reference to FIG. 10A. In this embodiment, each microphone 8110 or 8120 has three cardioid microphone elements 8111-8116. Conference participants such as reference numerals 8121, 8122 and 8123 can be seated anywhere in the conference room. Their voice is picked up by any one of the six cardioid microphone elements 8111 to 8116. Because they are placed overhead, ie above all participants, only direct speech 8132 and 8134 are accepted by the microphones 8110 and 8120. The first stage reflected voice or room echoes 8142 or 8144 are not accepted by the microphones 8110 and 8120. Loudspeakers 8102 and 8104 are provided to play speech from the end of the conference. Echoes or howlings between the microphone and the speaker are eliminated by acoustic signal processing. There are many effective methods for acoustic echo cancellation and howling cancellation. Any of them can be used in this embodiment of the invention. [0018] The installation of the overhead microphone array removes the microphones from the conference table in the conference room configuration. In contrast to typical tabletop microphones or speakers incorporating a microphone, the overhead microphone array does not interfere with the conference participants "out of sight". At the same time, the overhead microphones will acoustically "go into view" as compared to any desktop microphones. When there are several or more people in a conference, most people behind the first row do not have a direct view direction towards the table top microphone. Speech from those persons behind the first row is not well received by the microphone due to the obstruction of an object or person in between. On the other hand, overhead microphones are provided above all of the conference participants, regardless of how many people are in between. As long as the microphone is kept overhead, only its height is a design choice and almost an aesthetic choice. The microphones can be ceilings, below the ceiling and close to the ceiling, or slightly above them when people are 04-05-2019 7 sitting. Typically, the upper half of the room, ie, the space between the floor and the room ceiling to the room ceiling, is considered the room overhead space. In most conference rooms, there is nothing between the lower speaker in the room and the overhead microphone. The overhead microphone can always receive sound waves from any speaker in the room directly, so that the generated microphone signal has the best acoustic quality. [0019] In the embodiment shown in FIGS. 8 (a) and 8 (b), two microphones 8110 and 8120 can be used for the two acoustic channels. Those two independent acoustic channels can form a stereo sound field. They can be sent independently to other places in the conference. Similarly, at other locations, if multiple acoustic channels are set up and received by the local location, they will form a stereo sound field that distinguishes space. Spatial discriminatory stereo sound fields can be coupled with the video display to simulate a more life-like conferencing experience. [0020] FIG. 9 is a block diagram for signal processing for the embodiment shown in FIGS. 8 (a) and 8 (b). Microphone elements 8111 to 8116 are grouped into two sets of microphones. Microphone elements 8112, 8114 and 8116 are for microphone 8110 as shown in FIG. 8 (a) and microphone elements 8111, 8113 and 8115 are for microphone 8120. The signals from the microphone elements are provided to two steering controllers 942 and 941 respectively. The steering controllers 942 and 941 operate independently to form two separate acoustic channels. The operation of the steering controller 942 or 941 is the same to detect, select and mix the best signal quality from the microphone elements at the connected microphones. If one microphone element is identified as the best signal source, that signal passes as a signal 954 to downstream processing components. Signals from other elements are discarded. When more than one factor is selected, mixing occurs in the steering controller to generate signal 954. A similar process occurs to generate signal 953 from steering controller 941. The acoustic signal 954 or 953 is typically provided to a signal processor such as an acoustic echo canceller 962 or 961 to remove echo signals from the speakers in the conference room. The substantially echo-free signals 952 and 951 are then provided to the processor 971 for further processing, as required. For example, the acoustic signal can be frequency equalized to correct for non-flat frequency response, as shown in FIGS. Noise in the acoustic signal can be reduced to improve intelligibility, and white noise can be added to compensate for echo cancellation or noise reduction. The signal strength can also be adjusted to compensate for the different gains in the microphones. Acoustic signals can also be encoded for transmission in network systems such as, for example, the Internet, 04-05-2019 8 Integrated Services Digital Network (ISDN) or Plain Old Telephone Service (POTS). The conditioned signal 957 is sent to the other part of the conference. For clarity, steering, echo cancellation and other processing are shown to be performed by different processing. In actual embodiments, those functions tend to be performed by a single processor. The functions may also be separated and performed by two or more processes with different distributions of tasks. [0021] 10A-10B illustrate in more detail the overhead microphones used in the conferencing system shown in FIG. FIG. 10A (a) is a side view, and FIG. 10A (b) is a plan view. In this embodiment shown in FIG. 10A (a), it has a support structure 8223 with poles 8222 and the like. The support structure 8223 secures the microphone 8110 to the ceiling of the conference room. The lower end of the pole 8222 holds the main body of the microphone 8110. The microphone 8110 has three microphone elements 8112, 8114 and 8116. Each element is a cardioid microphone element. Each is spaced 120 ° apart from one another. In this way, the microphone 8110 can accept audio from the 360 ° range. If the microphone elements used in the microphones have different angular response ranges, the number of microphone elements used will be different. Each microphone element in the microphone is coupled to a microphone steering controller (not shown). The connection between the microphone element and the microphone steering controller can have many different ways. The processors can be located at different locations and connected to the microphone elements by simple wire connections. The wiring from the microphone element passes through the center of the support pole 8222 which penetrates the space above the ceiling to a controller located in the rest of the conference room. [0022] It is highly preferable in some situations to provide a processor mounted on the microphone so that only the processed microphone signal is transmitted to the acoustic system. FIG. 10A (c) shows a processor 8225 in the microphone 8110. In this way, less information may be required to be communicated between the microphone element and the controller. The processor may also perform other signal processing tasks, such as tasks related only to the microphone itself, such as acoustic gain control, frequency response equalization and noise reduction. Because the microphone element and the onboard signal processor are low power components, they can be powered by a small battery for an extended period of time. Also, with the additional wireless 04-05-2019 9 transceiver, which can be a low power consumption component, the microphone can be a wireless microphone that does not require a wired connection with an external system. Thus, the microphones are very flexible and can be easily added or removed from any position. The transceiver at the microphone can transmit its signal to an acoustic system that can communicate with the wireless microphone. [0023] In other embodiments, the microphone 8110 can also have a back shield 8220 positioned directly above the microphone element. Thus, any sound from above the back shield is shielded by the back shield 8220. For example, noise from above, such as noise from air conditioning vents, fluorescent lights, etc., is shielded from reaching the microphone elements. Since most ambient noise in the conference room is from overhead sources, placement of microphone elements with such back shields can alleviate the need for noise reduction processing. Another advantage of the back shield 8220 is that it can help to increase the microphone sensitivity gain when the speaker is directly below the microphone 8110. Sound pressure is doubled due to back shield boundary effects. This effect is used for superiority, as some of the acoustic energy is lost if the speaker is seated directly under the microphone 8110, due to diffraction of the speaker's head and due to the cardioid directivity. The doubled sound pressure compensates for the energy loss and helps equalize the response of the microphone elements. Due to the reduction of acoustic noise and the increase of acoustic signals, the need for signal processing, in particular the need for noise reduction, is reduced. [0024] The size of the back shield is variable. It is preferable to make the back shield as large as possible, i.e. very large in comparison to each microphone element, in order to receive the most benefit of shielding. When the microphone elements are arranged in a circle, the radius of the back shield 8220 is typically at least twice the radius of that circle 8121 as shown in FIG. 10A (b). The back shield can be made of any sound reflecting or sound absorbing material. Typical shield diameters are about 12 inches to 30 inches. [0025] A back shield can also be provided at each individual microphone element rather than one shield 04-05-2019 10 for all microphone elements. The back shield for each individual microphone element is smaller. For example, the individual shields 8132, 8134 and 8136 for the microphone elements 8112, 8114 and 8116, respectively, are smaller than the shield 8220. The individual shields can also be better directed to give better blocking of unwanted noise. [0026] Each microphone element can be placed separately or can be housed together in the same housing as shown in FIGS. 10B (f) and 10B (g). The lower portion of the housing 8224 is a sound wave from below and is, for example, sound transmissive (shown in dashed lines) to allow speech from a conference participant to reach the microphone element. The upper part (and the side of the housing, if necessary) is solid so as to be sound-permeable (indicated by a solid line). Sound waves from directions other than below can not reach the microphone element inside the housing. The housing 8224 itself can provide some shielding and reflective effects. A back shield 8220 is mounted directly above the microphone housing 8224 to provide good shielding. [0027] The overhead microphone assembly may be installed in a conference room and used in a conferencing system. The overhead microphone assembly can also be used in many other applications, such as, for example, video conferencing or conferencing in the room only. The sound system can amplify the participant's speech so that everyone in the room can hear the speech. Once the speech is captured by the overhead microphone assembly, the speech signal is, for example, amplified and reproduced at the same position, transmitted to the far end position, wirelessly broadcast, or recorded on permanent media for further reproduction. It can be used by any method such as [0028] The overhead microphone assembly as shown in FIGS. 10A (a) and 10A (b) is fixed in place by a hollow rod attached to the ceiling of the conference room. It can also be mounted in an appropriate position overhead by any other method. For example, the microphone can be attached to the bottom of the hanging luminaire or accessory. It can also be attached to a support arm extending from the wall. A vibration absorbing insulator can also be inserted between the microphone and its support structure or ceiling in order to reduce vibration noise from 04-05-2019 11 equipment in the building. [0029] Ceiling mounted microphones have been used in many prior art applications. Most of them are used for safety and surveillance purposes. In those applications it is not the fidelity of the sound, but the non-visibility of the microphone, for example the interest in the visual size of the microphone. Although some prior art ceiling mounted microphones are used in conference rooms, voice quality is less desirable. In particular, as noted above, omnidirectional microphone elements typically do not provide good quality acoustic signals in a conference room setting, especially when there are several people participating in the conference. [0030] In the present invention, an overhead microphone having a plurality of microphone elements is used. Microphones according to embodiments of the present invention can significantly improve voice quality, increase coverage, reduce acoustic noise levels received by the microphone, and reduce microphone interference by conference participants. It can greatly improve the liveliness of the conference call. [0031] Although the above example uses overhead microphones in a conference room, overhead microphones can be used in many other places where high quality microphones are desired. Such locations include, but are not limited to, classrooms, large halls, live art theaters, and the like. [0032] Although exemplary embodiments of the present invention have been described in detail with reference to the drawings, it will be understood that various modifications can be made without departing from the scope and spirit of the present invention. [0033] 04-05-2019 12 It is a figure shown about four kinds of microphone elements and those characteristics. It is a figure shown about the setting of a meeting room. Figures 3 (a) to 3 (c) illustrate an embodiment of the present invention in which three unidirectional microphone elements are used and oriented in the microphone. FIG. 5 compares the response of a microphone according to an embodiment of the present invention with the response of a representative omnidirectional microphone that is commercially available. FIG. 6 shows the frequency response of a microphone according to an embodiment of the present invention. FIG. 5 shows the angular response and frequency response of a microphone according to an embodiment of the present invention. FIG. 5 shows the angular response and frequency response of a microphone according to an embodiment of the present invention. FIGS. 8 (a) and 8 (b) are plan and side views, respectively, illustrating settings in a conference according to an embodiment of the present invention. FIG. 5 is a block diagram illustrating signal processing for a microphone. 10A (a) to 10A (c) are diagrams showing the physical arrangement of a portion of the ceiling module according to an embodiment of the present invention. 10B (d) to 10B (g) are diagrams illustrating the physical arrangement of a portion of the ceiling module according to an embodiment of the present invention. Explanation of sign [0034] 102 omnidirectional microphone 104 dipole microphone 106 cardioid microphone 108 high parker geoid microphone 202 microphone 210 conference participant 222 conference room table 232 speech 240 ceiling 242 wall 244 conference room arrangement 252 picture monitor 302 microphone element 304 microphone element 306 microphone element 310 Participants 312 Responses 314 Microphone Elements 320 Participants 330 Participants 412 Contours 414 Contours 510 Frequency Response Curves 610 Frequency Response Curves 702 High Angle Sound Collection Plot 704 High Angle Sound Collection Plot 706 High Angle Sound Collection Plot 708 High Angle Sound Collection Plot 712 High Angle Sound Collection Plot 714 High Angle Sound Collection Plot 8101 Video Monitor 8102 Speaker 8104 Speaker 8 05 Video Camera 8110 Overhead Microphone 8111 to 8116 Cardioid Microphone Element 8119 Conference Table 8120 Overhead Microphone 8121 to 8123 Conference Participant 8132 Back Shield 8134 Back Shield 8136 Back Shield 8220 Back Shield 8220 Pole 8222 Support Structure 8224 Housing 8225 Processor 941-942 Steering controller 953-954 Acoustic signal 957 Adjusted signal 961-962 Acoustic echo canceller 971 Processor 04-05-2019 13
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