This is a Bypass Continuation of PCT International Application PCT/JP2004/011675 filed on Aug. 6, 2004, and claims priority under 35 U.S.C. ยง119(a) from JP 2003-290686 filed on Aug. 8, 2003.
This invention relates to audio playback methods and apparatuses using line array speaker units, and in particular to multi-channel audio playback methods and apparatuses that are constituted by combining line array speaker units with television receivers and displays.
Recently, home theater systems, which give home users the feelings of being at live performances realized as visual and audio performances in theaters such as cinemas, have come to have a high popularity among people. A home theater system for home use is generally designed such that plural speakers are arranged to surround a listening position, and this is known as a 5.1-channel surround system. However, such an audio surround system constituted by plural speakers is complicated in wiring and is troublesome in setup due to limitations regarding arrangement of speakers. In addition, the audio surround system needs a relatively large space for installation. For this reason, the conventionally-known audio surround system cannot realize a simple system configuration for users who are to enjoy multi-channel audio.
There has been provided a technology for reproducing in an artificial manner audio surround effects using a 2-channel stereo speaker system, and this is known as an audio virtual surround system. However, it suffers from various problems such as artificiality in audio reproduction, limitations of listening environments, absence of feeling of being at a live performance, and degradation of sound quality. Hence, it has not come to be the current standard in home audio sound systems.
Recently, there has been provided another technology using a panel-type speaker array apparatus in which virtual sound sources are formed at prescribed positions surrounding a listener. This technology is disclosed in Japanese Patent Application Publication No. 2003-510924, a document provided by Pioneer Co. Ltd. (which can be retrieved via the Internet; URL: http://www.pioneer.co.jp/press/release 366-j.html), and a document regarding digital sound projectors provided by 1 Limited Co. (which can be retrieved via the Internet; URL: http://www.1 limited.com/lib/sound_projector_japanese.pdf), for example.
The aforementioned panel-type speaker array apparatus is constituted using plural speakers that are arrayed on a panel surface in a two-dimensional manner. The audio surround system using the panel-type speaker array apparatus performs delay control in such a way that sounds emitted by speakers focus on a single point in space, thus forming sound beams. The sound beams formed are reflected by wall surfaces in prescribed directions so as to form virtual sound sources surrounding a listener, thus realizing a multi-channel audio surround system using a single speaker array arranged in front of the listener.
The aforementioned audio surround system using the panel-type speaker array apparatus is capable of freely forming plural sound beams traveling in prescribed directions in front of a panel surface, and, it can freely localize sounds at prescribed positions with respect to separate channels. However, it is necessary to arrange numerous speakers (e.g., 254 speakers) in a two-dimensional manner in order to realize sound beam control having high directivity, and each speaker needs an audio circuit. Therefore, the aforementioned audio surround system is very expensive. In addition, it has problems due to the large overall area of a speaker array of a panel-type shape and a low degree of freedom regarding layout and setup position when it is combined with a display.
In consideration of the aforementioned circumstances, it is an object of this invention to provide a space-saving multi-channel audio playback system having a good live performance effect.
It is another object of this invention to realize a cost-saving speaker array for use in the aforementioned multi-channel audio playback system.
It is a further object of this invention to provide an audio playback system that is capable of freely controlling virtual sound sources and sound localization by use of sound beams, which are distributed in a sectorial form and are produced by means of line array speaker units each having limited directivity control.
This invention relates to an audio playback system using a line array speaker unit in which a plurality of speakers are arrayed in line, characterized in that the same audio signal is supplied to all speakers with prescribed delay times therefor so as to form a plurality of sound beams, thus forming a plurality of virtual sound sources, based on which a virtual sound image of the audio signal is formed at a prescribed position. In order to localize a virtual sound image, sound beams are appropriately controlled in emission direction and intensity.
In the above, it is not necessary to use a single line array speaker unit; instead, it is possible to use a plurality of line array speaker units, which are appropriately arranged and are combined with a display and the like. For example, line array speaker units may be arranged in a horizontal direction, a vertical direction, or a slanted direction, thus localizing a virtual sound image.
This invention will be described by way of a preferred embodiment with reference to the drawings.
In order to realize further controlling of high frequencies, and in order to increase the mixed audio output of speakers by increasing a density of arranging speakers, the speakers 2 are arranged alternately on the two surfaces of the enclosure 3 as shown in
Incidentally, it is possible to use generally-known cone-shaped speakers as the aforementioned speakers; and it is possible to use horn speakers, because they are expected to realize improvements with regard to directivity and sound emission efficiency in front of a panel. Alternatively, it is possible to use different types of speakers having different performances.
On the other hand, in a vertical plane perpendicular to the array of speakers forming a speaker array as shown in
Therefore, when audio signals are subjected to audio beam control in a line speaker array, it is possible to produce a sectorial distribution of sound beams spreading in a direction perpendicular to the speaker array, which is subjected to angular control in an axial direction of the speaker array.
An audio control method and an audio system, which realize the formation of a virtual sound image (fantom: a phantom or a phantom channel) in the rear of a listener by use of a line array speaker unit that is capable of forming sound beams, will be explained.
The aforementioned phantom indicates a phantom of a sound image (or a sound source) that is formed based on sound image localization using a 2-channel stereo system, and it is referred to as a phenomenon that allows a listener to sense the existence of a sound image at an intermediate position between his ears on the basis of a time difference and a volume difference between a sound heard at his right ear and a sound heard at his left ear in the head of the listener.
It is disclosed in the documents retrieved via the Internet that using an array speaker makes it possible to set a focal point of sound beams on a wall surface of a room, thus forming virtual sound sources on the wall surface. Using a speaker system of a matrix array as disclosed in the aforementioned documents makes it possible to form sound beams that are narrowed down sharply; hence, virtual sound sources formed on the wall surface can be directly used as surround sound sources. However, in the case of the line array speaker unit of this invention, sound beams are narrowed down into a sectorial form so that audio distribution thereof may slightly spread; therefore, it is difficult to use virtual sound sources directly, which are formed as described above, as surround sound sources.
For this reason, the present embodiment forms sound beams emitted in plural directions based on an audio signal of the same channel, thus forming plural broad virtual sound sources, whereby sound beam control is performed to form a phantom at a prescribed position in such a way that plural sounds emitted thereby reach and are picked up by left and right ears of a listener. This phantom is used as a surround sound source.
It is possible to form plural sound beams with respect to the same channel by use of a single line array speaker unit. Alternatively, it is possible to combine plural line array speaker units, which are arranged in different directions as shown in
Specifically,
In the second to sixth examples shown in
In the second example shown in
In the third example shown in
In the fifth example shown in
In the sixth example shown in
That is,
As described above, the line array speaker units can each form sound beams spreading in a broad sectorial form, whereas they may not form clear focal points. Due to the leading sound effect (or hearth effect), it is possible to set a virtual sound source on a wall surface in a direction in which sound reaches the listener first. Herein, the leading sound effect indicates psychoacoustic characteristics in which when the same sound reaches a listener with time differences from a relatively broad range of area, the listener may feel as if a sound image is localized in a direction, in which the sound reaches the listener first, within the range of area. Therefore, it is required that a virtual sound source be set on a wall surface (or a ceiling surface) in a direction, in which sound reaches the listener first; thus, a phantom is formed based on plural virtual sound sources, each of which is set up as described above.
Line array speaker units each have characteristics in which sound is localized in a relatively broad range of area. Hence, it is possible to reduce artificiality in which surround-channel sounds, which are produced upon the installation of surround speakers, become very clear in localization. Thus, it is possible to realize surround audio playback in a more natural manner.
In
Next, an audio playback apparatus for realizing a phantom localizing function using the aforementioned line array speaker unit will be explained.
As the audio source input to the aforementioned audio playback apparatus, it is possible to use 5.1-channel surround digital signals, for example. Such digital signals are divided into digital audio signals with respect to the channels by means of the decoder 10. Digital audio signals are input into the beam control block 12. The beam control block 12 is constituted using a digital signal processor (DSP).
The localization control block 11 is constituted using a microcomputer, which determines the following control parameters and sends them to the beam control block 12.
The outputs of the beam control units corresponding to the channels are added together by means of adders 123 with respect to the speakers and are then supplied to the audio circuit 13.
In
As described above, the audio playback method and apparatus of this invention do not use a panel-type array speaker but uses a combination of plural line array speaker units, each of which arrays plural speakers, so as to realize desired virtual sound sources and the localization of a phantom.
By appropriately changing the arrangement and structure of the line array speaker unit, sound beams emitted from the line array speaker unit can be distributed in a sectorial form, and virtual sound sources are formed at prescribed positions surrounding a listening position by combining sound beams reflected on wall surfaces of a room. A phantom is created and localized at a prescribed position between the virtual sound sources; hence, even though the line array speaker unit performs directivity control in a limited manner, it is possible to realize the positional setups for virtual sound sources with a relatively high degree of freedom similarly with a conventionally-known panel-type speaker array. This realizes the free formation of a sound field surrounding a listening position by use of a relatively small number of speakers.
That is, this invention compensates for the weakness of line array speaker units having limited directivity control by way of the localization of the phantom being created using sound beams spreading in a sectorial form. By appropriately setting the arrangement of plural line array speaker units, it is possible to freely localize sound at a desired position.
Furthermore, this invention can reduce the total number of speakers in comparison with the number of speakers used in the conventionally-known panel-type speaker array. This realizes a remarkable decrease in cost. Hence, it is possible to realize a maximal sound field reproduction effect with a minimal number of speakers.
Moreover, the overall area used for arranging line array speaker units can be reduced; and it is possible to freely set up the combination and formation therefor. This increases a degree of freedom with regard to the installation of line array speaker units, which can be easily combined together with a display.
Incidentally, this invention is not necessarily limited to the aforementioned embodiments; hence, variations within the scope of the invention are intended to be embraced by this invention.
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Number | Date | Country | |
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Parent | PCT/JP2004/011675 | Aug 2004 | US |
Child | 11348555 | US |