Multi-Channel Surround Systems such as Dolby Atmos and DTS-X employ a large number of speakers to render realistic movement of sound inside a theater. A large collection of speakers is housed on the theater walls and on the ceiling. The target sound “object” in the case of Dolby Atmos is rendered by injecting appropriate sound information to nearby set of speakers. In a movie theater, a large collection of speaker installation is not a problem. However, when such a system is aimed towards home applications, cost-effective and performance-preserving solutions become very difficult to achieve. In a home theater application, the volume and space occupied by the speaker system is judged to be premium and expensive. Homeowners prefer small and compact home theater equipment. Installing speaker units on the ceiling of living room will be rejected by the homeowner. The user preference is to have a minimum of equipment yet have the best sound mimicking what is heard at the movie theater.
Embodiments are directed to a speaker array for home theater and mini theater applications. In some embodiments, a speaker array is built by placing multiple speakers around a subwoofer speaker in a cylindrical enclosure. The speaker array may provide a good trade-off between the amount of equipment and the theatre-quality sound produced. The cylindrical speaker array can be placed on the floor level as a single unit for small home living room or multiple units for a large performance space. The multiple units deployed can coordinate with each other. The cylindrical speaker array can be static, static with space measurement sensors, or moving with a motion-controlled platform.
In some embodiments, the internal placement of speakers inside the cylindrical enclosure may be done by housing the speakers on an annular elliptical surface. Referring to
While the foregoing embodiments illustrate the placement of speakers in a cylindrical tube, in other embodiments, the speakers can be placed in tubes of non-cylindrical shapes, e.g., rectangular tube.
Decoding Surround Sound Inputs
Surround sound stream is encoded digitally and is compressed with encoding technologies like for example, Dolby Atmos or DTS-X. The compressed stream is first demultiplexed to extract individual surround channels and decoded to obtain individual digital samples. If the total number of individual input sound channels is P comprising of S subwoofer and H height channels, then remaining (P-S-H) channels contain directional spatial sound. This arrangement is commonly denoted by [(P-S-H).S.H]. A height channel creates the impression of sound entering from the ceiling. These details are well known to a practitioner of this technology and will not be elaborated in this invention disclosure.
Speaker Enclosure to Enhance Performance
In a speaker system, an enclosure with a port (also known as a vented enclosure) is necessary to maximize the sound pressure from the speaker. Techniques used in such a design are well known to the designers in the field. Hence the placement of a speaker at a location in 3D space also includes its ported enclosure. Again, details are omitted here. Another possibility is to employ a set of passive radiators to boost the low frequency response.
Subwoofer Integration
Placement and installing subwoofer in the center of annular space requires special considerations to allow both high frequency and low frequency vibrations from speakers and the subwoofer exist without restricting or interfering with each other. The engineering design is well known to the practitioners of the art.
Signal Processing for Surround Sound
1. Energy Equalization at a Set of Distant Points—Multi-Channel Multi-Beam Forming
Let the 3D coordinates of all N speakers be given by
where (xiyizi) is the coordinates of the i-th speaker. In general, all speakers occupy different 3D locations.
Let there be a set of distant points {Fi} with coordinates {fxifyifzi} for i=1, 2, 3, . . . P where we want to maximize the audio energy by bringing all the speaker outputs in phase so as to add up to a maximum energy level. The necessary condition for this to happen is to find a set of integers {d1i, d2i, d3i, . . . dNi} and short M-length filters {h1i, h2i, h3i, . . . hNi} such that the input signal to the speakers from the i-th surround input {xi [k]} for i=1, 2, 3, . . . P and k=0, 1, 2, 3 . . . is generated in the following way:
which means that the n-th speaker receives the signal:
The solution {d1i, d2i, d3i, . . . dNi} is obtained by computing the Euclidian distance between Sxyx and {Fi} and making the distances equal with the constraint that the set {d1i, d2i, d3i, . . . dNi} must contain only positive integers. The M-length filters {h1i, h2i, h3i, . . . hNi} are chosen to make phase angle continuities are maintained while preserving wide bandwidth needed. This means that given the speaker positions Sxyx and {Fi}, P×N table containing {d1i, d2i, d3i, . . . dNi} and M×N×P table containing {h1i, h2i, h3i, . . . hNi} can be precomputed and stored in the memory. As the samples from each input channel arrive, the equation (2) is implemented as a matrix filter operation. The implementation of (2) is a well-known art in the discipline of digital signal processing with a FPGA or a custom ASIC.
2. Codebook Generation of {Fi} for Sound Panorama
As shown in
3. Psycho-Acoustic Benefits
The above strategy of using rectangular decompositions of living room geometry has the benefit of accentuating the “first wavefront”, (see the discussion in section 3.4 of [7]) to reinforce the perception of directional sound, (see chapter 5.4 in [13]). In addition, the process of generating surround signals in either Dolby Atmos or DTS-X exaggerates the directional information to catch the attention of the listener. The “late reverberations” arising due to geometry of the living room also are helpful in “tuning-in” to the directionality of the surround sound. As a result of these additive reinforcements, the sound rendered from the array is heard as clearly directional.
4. Speaker Equalization
In order to control the frequency spectral properties of the speakers, multi-band equalization is employed. A bi-quad IIR filter is described by z-domain the transfer function
A cascade of B such filters constitutes a combined transfer function of
H(z)=Πi=1BHi(z) (4)
and is useful for making frequency spectrum even and pleasant for human ears. The digital implementation of these cascaded filters is a well-known prior art, see [14], [15], and [16]. The tuning of filters is done by a graphical user interface that controls the spectral bands by adjusting the bi-quad filter coefficients.
5. Digital Implementation of the Entire System with a FPGA
A Field Programmable Gate Array (FPGA) contains a collection of complex logic blocks that be rearranged as multipliers, adders, logic gates, memories, and other higher order functional blocks in a vendor-supplied library. Depending on the vendors—Xilinx, Altera (now owned by Intel), Actel, and Lattice—different adjustments and restructuring of synthesis code written in either Verilog or VHDL is necessary. The art and science of implementation with FPGA is readily available in [14]. The aim in design is to recast divisions as multiplications and additions and (re)use the multipliers. Another consideration is timing synchronization between different branches of the solution. FPGA implementation helps in the path towards building a custom ASIC. The digital design described here is done for at least three different family of FPGAs and verified for functionality.
Swarm Speaker Arrays
A swarm of speaker arrays includes a number of speaker arrays, as illustrated in
Once the 3D map of the environment is obtained, as shown
Extending to a large number of speaker arrays, as shown in
Since a single member of swarm speaker array, as shown in
Conversely if the listener occupancy map in 2-D space is available, the swarm can be made to track the areas where listeners sit. A contact switch can be placed in every seat of the listening room to transmit a binary signal to indicate if the seat is occupied or not. With this binary occupancy map, the swarm can reorient to provide the best possible over all listening experience to all present in the listening room. The algorithms needed to implement automatic tracking of listener positions are readily available to any practitioner of the art using the formulation of maximization of overall signal level in the room. With swarms with motion capability this can be done in almost real-time. Listener position tracking can also be done using cameras. In some embodiments, as the listener position changes, the speaker arrays may automatically change their position or orientation to provide the best possible over all listening experience to the listener.
The swarm speaker array may be configured to control positioning (e.g., including orientation) of a speaker array in the swarm. For example, a speaker array in the swarm may be mounted on a motion-controlled platform that can be controlled to move the speaker array to adjust the position. Various motion-controlled platforms can be implemented. For example, the motion-controlled platform can be implemented as robotic platform with wheels as illustrated in
A few features of the speaker array include:
In some embodiments, the various embodiments described herein may use one or more computing devices that are programmed to perform the functions described herein. The computing devices may include one or more electronic storages, or other electronic storages), one or more physical processors programmed with one or more computer program instructions, and/or other components. The computing devices may include communication lines or ports to enable the exchange of information within a network or other computing platforms via wired or wireless techniques (e.g., Ethernet, fiber optics, coaxial cable, Wi-Fi, Bluetooth, near field communication, or other technologies). The computing devices may include a plurality of hardware, software, and/or firmware components operating together. For example, the computing devices may be implemented by a cloud of computing platforms operating together as the computing devices.
The electronic storages may include non-transitory storage media that electronically stores information. The storage media of the electronic storages may include one or both of (i) system storage that is provided integrally (e.g., substantially non-removable) with servers or client devices or (ii) removable storage that is removably connectable to the servers or client devices via, for example, a port (e.g., a USB port, a firewire port, etc.) or a drive (e.g., a disk drive, etc.). The electronic storages may include one or more of optically readable storage media (e.g., optical disks, etc.), magnetically readable storage media (e.g., magnetic tape, magnetic hard drive, floppy drive, etc.), electrical charge-based storage media (e.g., EEPROM, RAM, etc.), solid-state storage media (e.g., flash drive, etc.), and/or other electronically readable storage media. The electronic storages may include one or more virtual storage resources (e.g., cloud storage, a virtual private network, and/or other virtual storage resources). The electronic storage may store software algorithms, information determined by the processors, information obtained from servers, information obtained from client devices, or other information that enables the functionality as described herein.
The processors may be programmed to provide information processing capabilities in the computing devices. As such, the processors may include one or more of a digital processor, an analog processor, a digital circuit designed to process information, an analog circuit designed to process information, a state machine, and/or other mechanisms for electronically processing information. In some embodiments, the processors may include a plurality of processing units. These processing units may be physically located within the same device, or the processors may represent processing functionality of a plurality of devices operating in coordination. The processors may be programmed to execute computer program instructions to perform functions described herein. The processors may be programmed to execute computer program instructions by software; hardware; firmware; some combination of software, hardware, or firmware; and/or other mechanisms for configuring processing capabilities on the processors.
Remarks
The above description and drawings are illustrative and are not to be construed as limiting. Numerous specific details are described to provide a thorough understanding of the disclosure. However, in some instances, well-known details are not described in order to avoid obscuring the description. Further, various modifications may be made without deviating from the scope of the embodiments. Accordingly, the embodiments are not limited except as by the appended claims.
Reference in this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the disclosure. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Moreover, various features are described which may be exhibited by some embodiments and not by others. Similarly, various requirements are described which may be requirements for some embodiments but not for other embodiments.
The terms used in this specification generally have their ordinary meanings in the art, within the context of the disclosure, and in the specific context where each term is used. Terms that are used to describe the disclosure are discussed below, or elsewhere in the specification, to provide additional guidance to the practitioner regarding the description of the disclosure. For convenience, some terms may be highlighted, for example using italics and/or quotation marks. The use of highlighting has no influence on the scope and meaning of a term; the scope and meaning of a term is the same, in the same context, whether or not it is highlighted. It will be appreciated that the same thing can be said in more than one way. One will recognize that “memory” is one form of a “storage” and that the terms may on occasion be used interchangeably.
Consequently, alternative language and synonyms may be used for any one or more of the terms discussed herein, nor is any special significance to be placed upon whether or not a term is elaborated or discussed herein. Synonyms for some terms are provided. A recital of one or more synonyms does not exclude the use of other synonyms. The use of examples anywhere in this specification including examples of any term discussed herein is illustrative only, and is not intended to further limit the scope and meaning of the disclosure or of any exemplified term. Likewise, the disclosure is not limited to various embodiments given in this specification.
Those skilled in the art will appreciate that the logic illustrated in each of the flow diagrams discussed above, may be altered in various ways. For example, the order of the logic may be rearranged, substeps may be performed in parallel, illustrated logic may be omitted; other logic may be included, etc.
Without intent to further limit the scope of the disclosure, examples of instruments, apparatus, methods and their related results according to the embodiments of the present disclosure are given below. Note that titles or subtitles may be used in the examples for convenience of a reader, which in no way should limit the scope of the disclosure. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. In the case of conflict, the present document, including definitions will control.
All the above references are incorporated herein by reference.
The present application claims priority to U.S. Provisional Patent Application No. 62/978,421 filed on Feb. 19, 2020 entitled “SPEAKER ARRAY FOR MULTI-CHANNEL SURROUND SOUND HOME”, the contents of which are incorporated by reference in their entirety.
Number | Name | Date | Kind |
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20100135505 | Graebener | Jun 2010 | A1 |
Number | Date | Country |
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4422500 | Mar 1995 | DE |
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62978421 | Feb 2020 | US |