Patent Application
20120039475
This specification describes an audio system for a television employing directional audio devices.
In one aspect an audio system includes at least a left channel, a right channel, and a center channel. The audio system includes a crossover network for separating the left channel, the right channel, and the center channel into low frequency content, midrange frequency content, and high frequency content; an omnidirectional acoustical device for radiating acoustic energy corresponding to the low frequency content of the combined left channel, right channel, and center channel; a first directional array comprising signal processing circuitry and more than one acoustic driver, for radiating acoustic energy corresponding to the midrange content of one of the left channel and right channel signal so that more acoustic energy corresponding to the midrange content of one of the left channel signal and the right channel signal is radiated laterally than in other directions; and a first passive directional device, for radiating acoustic energy corresponding to the high frequency content of the one of the left channel and right channel signal so that more acoustic energy corresponding to the high frequency content of the one of the left channel signal and the right channel signal is radiated laterally than in other directions. The audio system may include a second directional array for radiating acoustic energy, comprising signal processing circuitry and more than one acoustic driver for radiating acoustic energy corresponding to the midrange content of the other of the left channel and right channel so that more acoustic energy corresponding to high frequency content of the other of the left channel and right channel signal is radiated laterally than in other directions; and a second passive directional device, for radiating acoustic energy corresponding to the midrange content of the other of the left channel and right channel so that more acoustic energy corresponding to high frequency content of the other of the left channel and right channel signal is radiated laterally than in other directions. The first directional array, the second directional array, the first passive directional device and the second passive directional device may be mounted in a common enclosure. The common enclosure may be a television cabinet. The first directional array and the second directional array may include at least one common driver. The audio system of may further include a third directional array for radiating acoustic energy, comprising signal processing circuitry and more than one acoustic driver for radiating acoustic energy corresponding to the midrange content of the center channel so that more acoustic energy corresponding to the center channel signal is radiated in a direction substantially orthogonal to the direction of greater radiation of the first directional array and the direction of greater radiation of the second directional array. The audio system may further include a non-directional high frequency acoustical device for radiating the high frequency content of the center channel. The non-directional high frequency device and the third directional array may positioned in a television on vertically opposite sides of a television screen. At least two of the first directional array, the second directional array, and the third directional array may include at least one acoustic driver in common. The direction substantially orthogonal to the direction of greater radiation of the first directional array and the direction of greater radiation of the second directional array is substantially upward. The direction substantially orthogonal to the direction of greater radiation of the first directional array and the direction of greater radiation of the second directional array may be substantially toward an intended listening area. The omnidirectional device may include a waveguide. The waveguide may be mounted in a television cabinet. At least two of the first directional array, the second directional array, and the third directional array include more than one acoustic driver in common. The first directional array, the second directional array, and the third directional array may include more than one acoustic driver in common. The audio system may be mounted in a television cabinet. The omnidirectional acoustical device, the first directional array, the second directional array, the third directional array, the first passive directional device, and the second passive directional device each have an exit through which acoustic energy is radiated to the environment, and none of the exits may be in a front face of the television cabinet. The first passive directional device may include a slotted pipe type passive directional acoustic device comprising an acoustic driver, acoustically coupled to a pipe to radiate acoustic energy into the pipe. The pipe may include an elongated opening along at least a portion of the length of the pipe; and acoustically resistive material in the opening through which pressure waves are radiated to the environment. The pressure waves characterized by a volume velocity. The pipe, the opening, and the acoustically resistive material may be configured so that the volume velocity is substantially constant along the length of the pipe.
In another aspect, a method for operating an audio system comprising at least a left channel, a right channel, and a center channel, includes radiating omnidirectionally acoustic energy corresponding to the low frequency content of the combined left channel, right channel, and center channel; radiating directionally, from a first directional array comprising signal processing circuitry and more than one acoustic driver, acoustic energy corresponding to the midrange content of the left channel so that more acoustic energy corresponding to the left channel signal is radiated leftwardly than in other directions; radiating directionally, from a second directional array comprising signal processing circuitry and more than one acoustic driver, acoustic energy corresponding to the midrange content of the right channel so that more acoustic energy corresponding to the right channel signal is radiated rightwardly than in other directions; radiating directionally, from a third directional array comprising signal processing circuitry and more than one acoustic driver, acoustic energy corresponding to the midrange content of the center channel so that more acoustic energy corresponding to the center channel signal is radiated in a direction substantially orthogonal to the direction of greater radiation of the first directional array and the direction of greater radiation of the second directional array; radiating directionally, from a first passive directional device, acoustic energy corresponding to the high frequency content of the left channel so that more acoustic energy is radiated leftwardly than other directions; and radiating directionally, from a second passive directional device, acoustic energy corresponding to the high frequency content of the right channel so that more acoustic energy is radiated rightwardly than other directions. The method may further include radiating non-directionally the high the high frequency content of the center channel. Radiating non-directionally the high frequency content of the center channel may include radiating from a vertically opposite side of a television screen from the radiating directionally of the midrange content of the center channel. The radiating omnidirectionally acoustic energy corresponding to the low frequency content of the combined left channel, right channel, and center channel may include radiating from a waveguide. 2.2.1. The radiating omnidirectionally may include radiating from a waveguide is mounted in a television cabinet. The directionally radiating in a direction substantially orthogonal to the direction of greater radiation of the first directional array and the direction of greater radiation of the second directional array may include radiating substantially upward. The directionally radiating in a direction substantially orthogonal to the direction of greater radiation of the first directional array and the direction of greater radiation of the second directional array may include radiating substantially toward an intended listening area. The radiating directionally from a first directional array, the radiating directionally from a second directional array, the radiating directionally from a third directional array, the radiating directionally from a first passive directional device and the radiating directionally from a second passive directional device may include radiating from a television cabinet. The radiating directionally from a first directional array, the radiating directionally from a second directional array, the radiating directionally from a third directional array, the radiating directionally from a first passive directional device and the radiating directionally from a second passive directional device may include radiating from one of a side, a bottom, or a top of a television cabinet.
In another aspect, an audio system for a television may include a television cabinet; a slotted pipe type passive directional acoustic device that includes an acoustic driver, acoustically coupled to a pipe to radiate acoustic energy into the pipe. The pipe may include an elongated opening along at least a portion of the length of the pipe; and acoustically resistive material in the opening through which pressure waves are radiated to the environment. The pressure waves may be characterized by a volume velocity. The pipe, the opening, and the acoustically resistive material may be configured so that the volume velocity is substantially constant along the length of the pipe. The passive directional acoustic device may be mounted in the television cabinet to directionally radiate sound waves laterally from the television cabinet. the pipe may be at least one of bent or curved. The opening may be at least one of bent or curved along its length. The opening may be in a face that is bent or curved. The television cabinet may be tapered backwardly, and the passive directional acoustic device may be mounted so that a curved or bent wall of the slotted pipe type passive directional acoustic device is substantially parallel to the back and a side wall of the television cabinet. The opening may include two sections, a first section in a top face of the pipe and a second section in a side face of the pipe. The audio system for a television of claim 10.0, wherein the acoustic apparatus may be for radiating the high frequency content of a left channel or a right channel laterally from the television. The passive directional acoustic device may be for radiating the left channel or right channel content above 2 kHz. The audio system may further include a directional array for radiating midrange frequency content of the left channel or right channel laterally from the television. The audio system may further include a waveguide structure for radiating bass frequency content of the left channel or right channel; the other of the left channel or right channel; and a center channel. The cross sectional area of the pipe may decrease along the length of the pipe.
Other features, objects, and advantages will become apparent from the following detailed description, when read in connection with the following drawing, in which:
Though the elements of several views of the drawing may be shown and described as discrete elements in a block diagram and may be referred to as “circuitry”, unless otherwise indicated, the elements may be implemented as one of, or a combination of, analog circuitry, digital circuitry, or one or more microprocessors executing software instructions. The software instructions may include digital signal processing (DSP) instructions. Operations may be performed by analog circuitry or by a microprocessor executing software that performs the mathematical or logical equivalent to the analog operation. Unless otherwise indicated, signal lines may be implemented as discrete analog or digital signal lines, as a single discrete digital signal line with appropriate signal processing to process separate streams of audio signals, or as elements of a wireless communication system. Some of the processes may be described in block diagrams. The activities that are performed in each block may be performed by one element or by a plurality of elements, and may be separated in time. The elements that perform the activities of a block may be physically separated. One element may perform the activities of more than one block. Unless otherwise indicated, audio signals or video signals or both may be encoded and transmitted in either digital or analog form; conventional digital-to-analog or analog-to-digital converters may not be shown in the figures. For simplicity of wording “radiating acoustic energy corresponding to the audio signals in channel x” will be referred to as “radiating channel x.” “Directional arrays”, as used herein, refers to arrays that use a combination of signal processing and geometry, placement, and configuration of more than one acoustic driver to cause the radiation to be greater in some directions than in other directions. Directional arrays include interference arrays, such as described in U.S. Pat. No. 5,870,484 and U.S. Pat. No. 5,809,153. “Passive directional device”, as used herein, refers to devices that do not use any signal processing, but rather use only mechanical or physical arrangements or devices to cause the radiation of wavelengths that are large (for example 2×) relative to the diameter of the radiating elements to be greater in some directions than in others. Passive directional devices could include acoustic lenses, horns, dipole radiators, or slotted pipe type directional devices shown below and in
The left channel midrange (LM) frequency sound is radiated by a directional array so that more acoustic energy is radiated laterally leftward relative to a listening area than in other directions as indicated. The right channel midrange (RM) frequency sound is radiated by a directional array so that more acoustic energy is radiated laterally rightward than in other directions as indicated.
The left channel high (LH) frequency sound is radiated by a passive directional device so that more acoustic energy is radiated laterally leftward than in other directions as indicated. The right channel high (RH) frequency sound is radiated by a passive directional device so that more acoustic energy is radiated laterally rightward than in other directions as indicated.
Radiating the left and right channels directionally laterally causes more of radiation experienced by the listener to be indirect radiation than direct radiation or radiation of the left and right channels toward the listening area. Causing more of the radiation to be indirect radiation results in a more spacious acoustic image and permits the radiation of the left and right channels from a device in the lateral middle of the listening area.
In
In
When implemented in a television, the center channel high frequency acoustical device may be vertically on the opposite side of the television screen from the center channel directional array to cause the acoustic image to be vertically centered on the television screen. For example, as shown in
The left channel signal L, the right channel signal R, and the center channel signal C are combined at signal summer 29 and low pass filtered by low pass filter 24 to provide a combined low frequency signal. The combined low frequency signal is radiated by a low frequency radiation device 26, such as a woofer or another acoustic device including low frequency augmentation elements such as ports, waveguides, or passive radiators. Alternatively, the left channel signal, the right channel signal, and the center channel signal may be low pass filtered, then combined before being radiated by the low frequency radiation device, as shown in
In
The right channel signal is band pass filtered by band pass filter 28 and radiated directionally by right channel array 38 as shown in
The center channel signal is band pass filtered by band pass filter 28 and radiated directionally by center channel array 44 as shown in
In one implementation, the break frequency of low pass filter 24 is 250 Hz, the pass band for band pass filter 28 is 250 Hz to 2.5 k Hz, and the break frequency for high pass filter 32 is 2 kHz.
In one implementation, the low frequency device 26 of
Directional arrays 30, 38, and 44 are shown diagrammatically in
The directional radiation patterns of the midrange frequency bands of
In operation, the left channel signal L, as modified by the transfer functions H1L(z)-H5L(z) is transduced to acoustic energy by the acoustic drivers 218-1-218-5. The radiation from the acoustic drivers interferes destructively and non-destructively to result in a desired directional radiation pattern. To achieve a spacious stereo image, the left array 232 directs radiation laterally toward the left boundary of the room as indicated by arrow 213 and cancels radiation toward the listener. The use of digital filters to apply transfer functions to create directional interference arrays is described, for example, in Boone, et al., Design of a Highly Directional Endfire Loudspeaker Array, J. Audio Eng. Soc., Vol 57. The concept is also discussed with regard to microphones van der Wal et al., Design of Logarithmically Spaced Constant Directivity—Directivity Transducer Arrays, J. Audio Eng. Soc., Vol. 44, No. 6, June 1996 (also discussed with regard to loudspeakers), and in Ward, et al., Theory and design of broadband sensor arrays with frequency invariant far-field beam patterns, J. Acoust. Soc. Am. 97 (2), February 1995. Mathematically, directional microphone array concepts may generally be applied to loudspeakers.
Similarly, in
In operation, the right channel signal R, as modified by the transfer functions H3R(z)-H7R(z) is transduced to acoustic energy by the acoustic drivers 218-3-218-7. The radiation from the acoustic drivers interferes destructively and non-destructively to result in a desired directional radiation pattern. To achieve a spacious stereo image, the right array 234 directs radiation laterally toward the right boundary of the room as indicated by arrow 215 and cancels radiation toward the listener.
In
In operation, the center channel signal C, as modified by the transfer functions H2C(z)-H6C(z) is transduced to acoustic energy by the acoustic drivers 218-2-218-6. The radiation from the acoustic drivers interferes destructively and non-destructively to result in a desired directional radiation pattern.
An alternative configuration for the center channel array 44 is shown in
In operation, the center channel signal C, as modified by the transfer functions H1C(z), H3C(z)-H5C(z)), and H7C(z) is transduced to acoustic energy by the acoustic drivers 218-1, 218-3-218-5, and 218-7. The radiation from the acoustic drivers interferes destructively and non-destructively to result in a desired directional radiation pattern.
The center channel array 44 of
Other types of directional array are appropriate for use as directional arrays 30, 38, and 44. For example, each of the arrays may have as few as two acoustic drivers, without any acoustic drivers shared by arrays.
In one implementation, the left passive directional device 34 and the right passive directional device 42 of
The passive directional device 310 of
In the actual implementation of
The implementation of the slotted pipe type directional loudspeaker of
Other types of passive directional devices may be appropriate for passive directional devices 32 and 42, for example, horns, lenses or the like.
Using passive directional devices for high frequencies is advantageous because it provides desired directionality without requiring directional arrays. Designing directional arrays that work effectively at the short wavelengths corresponding to high frequencies is difficult. At frequencies with corresponding wavelengths that approach the diameter of the radiating elements, the radiating elements themselves may become directional.
Numerous uses of and departures from the specific apparatus and techniques disclosed herein may be made without departing from the inventive concepts. Consequently, the invention is to be construed as embracing each and every novel feature and novel combination of features disclosed herein and limited only by the spirit and scope of the appended claims.
