Electrical audio signal processing systems and devices – Directive circuits for microphones
Reissue Patent
2000-06-15
2003-12-16
Mei, Xu (Department: 2644)
Electrical audio signal processing systems and devices
Directive circuits for microphones
C381S026000, C381S122000, C381S355000, C381S356000
Reissue Patent
active
RE038350
ABSTRACT:
FIELD OF THE INVENTION
This invention relates in general to microphone systems and more particularly to global sound microphone systems which are portable.
BACKGROUND OF THE INVENTION
There are a number of existing “surround sound” systems which use digital or analogue equipment to record and reproduce sound. The goal of such systems is to recreate the sound environment. To recreate a sound environment, the surround sound system must be designed with an awareness of the human brain's ability to determine, within all three dimensions, where a given sound originates. The ear has two independent functions, one, to hear (auditory), the other to sense the motion of the listener or of an object in space identified by the listener (vestibular). Realistic sound production must give the listener a sense of vestibular as well as auditory function, thus, the motion of the listener or object in space identified by the listener is important to the perception of reality. The brain is able to recognize small differences in loudness and timing in soundwaves as they reach both the left and right ears so as to exactly localize and follow a sound source in space.
Systems are known in the art which exploit this fact. An example is the binaural system which uses two audio channels to record sound. The binaural system is able to achieve excellent results but the listener must wear headphones to experience the surround sound effect. Otherwise the reproduction is the equivalent of a traditional stereo, two-dimensional, recording.
Quadraphonic sound systems have also been devised. Such systems employ four audio channels in a “double stereo” pattern to provide a more realistic localization effect for the listener. This format has not achieved universal acceptance due to the fact that while it was meant for consumer use, there was not enough material available that was recorded for four channels. A special microphone, the Caldrec Soundfield, was developed to record quadraphonically by using four microphone diaphragms and four channels. The diaphragms can be electronically “zoomed” in on a specific channel. The limitation of this process is that the microphone must remain stationary in order for the signal levels received at the microphone diaphragms to remain uniform; it also only has four channels.
Multi-channel, surround sound audio systems are now widely accepted in the professional audio market. It is virtually a standard in major motion picture theatres worldwide. The technology is also becoming more commonplace in the consumer audio market. The public theatre and the private livingroom are now places where a realistic, natural sound environment can be created.
A typical surround sound environment consists of five to ten speakers placed around a room in several different configurations. In a movie theatre, for example, there may be three speakers behind the projection screen (left-centre, centre, and right-centre), two speakers at the sides of the room (left and right) and two speakers at the rear of the room (left and right surround). Each of these speakers is assigned its own specific channel. During the recording of the live sound sources for surround sound applications, the microphones are set up in a stationary position at approximately the site at which the sound will be heard though the coincident monitor speaker of the surround sound system. This technique works well, only if the perspective of the listener/viewer is meant to be stationary in relation to the sound. As a result, the listener's position, perceived or actual, must remain stationary and cannot move in relation to the sound. An example of this situation occurs when a camera moves or pans on an object which the listener is focusing his attention through a scene such as a jungle or a city street and surround sound is required to accompany it.
At the recording studio during final mixdown of the soundtrack, by using special multi-channel signal processors, an audio technician is able to take any recorded signal and sonically move that signal between any number of the channels, or speakers, in the system, thus creating the illusion that the sound is actually moving from one part of the listening environment to the other. Although this appears as an interesting effect it has been manipulated by a processor and though it may appear natural, it is not.
Thus a global microphone system which is able to be used to reproduce “surround sound” and which does not require headphones, which does not have to remain stationary, and which is able to create the effect of motion and exact specific auditory localization of the object in motion without using the mixing process, is desirable.
SUMMARY OF THE INVENTION
An object of one aspect of the present invention is to provide an improved type of microphone system.
In accordance with one aspect of the present invention there is provided a microphone system having a portable frame for mounting a plurality of microphones, each microphone of the plurality of microphones having a diaphragm, the plurality of microphones comprising a set of linear pick-up pattern microphones, whereby when mounted, each one of the set of linear pick-up microphones has its diaphragm facing outwards from the frame and the diaphragms of the set of microphones form a generally elliptical pattern.
Conveniently, the means for mounting a plurality of microphones further comprises a means for mounting a microphone having a substantially hemispherical pick-up pattern at a location within the generally elliptical pattern of the linear pattern microphones.
Preferably, the means for mounting a microphone having a substantially hemispherical pick-up pattern maintains the orientation of the microphone such that the hemispherical pick-up pattern of the microphone is normal to the plane of the elliptical pattern of the linear pattern microphones and the substantially hemispherical pick-up pattern is directed upwards.
Preferably, the means for mounting a plurality of microphones further comprises a second means for mounting a second microphone having a substantially hemispherical pick-up pattern at a location within the generally elliptical pattern and the second means for mounting a second microphone having a substantially hemispherical pick-up pattern is adapted to maintain the orientation of the second microphone such that the hemispherical pick-up pattern of the second microphone is normal to the plane of the elliptical pattern and is directed downwards.
Preferably, each microphone of the set of linear pick-up pattern microphones has a hypercardioid or other linear pick-up pattern.
Preferably there is provided a means for mounting one of the set of microphones at a position at a one end of the generally elliptical shape and means for mounting the set of the microphones in a generally equispaced relationship about the elliptical shape.
Conveniently, there is provided a hand grip depending downwards from the frame, alternatively the frame is attached to a camera.
Advantageously, there is provided a multi-channel audio mixer, means for electrically connecting each one of the set of the microphones with a one of the channels of the multi-channel mixer and a means for operatively connecting the multi-channel mixer with a digital multi-channel sound recording device or any advance on that technology.
Advantageously, there is provided a means for selectively electronically connecting and disconnecting ones of the set of microphones to adapt the system for a predetermined sound playback configuration.
Advantages of the present invention are that a portable system to faithfully, reproduce multiple sounds as recorded, and which permits recording while the object/system is in motion, is provided.
An advantage of an embodiment of the present invention is that the sound recorded is “rounded out”.
A further advantage of an embodiment of the invention is that the microphone system may be hand-held.
An advantage of an embodiment of the invention is that the microphone system may be used in conjunction with a camera to achieve holographic soni
Brady O'Boyle & Gates
Mei Xu
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