Claims
- 1. A system for reproducing at least first and second electro-acoustic signals each corresponding to a different channel of a multi-channel electronic musical instrument comprising, in combination:
- an acoustic processing unit, said acoustic processing unit comprising:
- a substantially sealed enclosure having at least first and second openings in a wall thereof,
- acoustic transmission means defining first and second acoustic output ports acoustically coupled to said first and second openings, respectively,
- at least first and second electro-acoustic transducers mounted on said wall over said at least first and second openings, respectively, each connected to receive an electro-acoustic signal from a respective one of said channels for converting said electro-acoustic signals to corresponding acoustic signals and supplying acoustic power only to a respective output port and so arranged relative to each other that an electrically energized transducer mechanically induces substantially corresponding vibrations in the other transducers; and
- sound reproducing means coupled to the acoustic output ports of said acoustic processing unit for reproducing the sound signals supplied thereto.
- 2. System according to claim 1, wherein said sound reproducing means comprises a pair of acoustic transmission paths coupled to respective acoustic output ports of said acoustic processing unit for transmitting said respective sound signals directly toward the left and right ears of a listener as direct sounds.
- 3. System according to claim 2, wherein said acoustic transmission paths are hollow tubes of the same diameter each connected at one end to a respective acoustic output port.
- 4. System according to claim 3, wherein said tubes are of substantially the same length.
- 5. System according to claim 1, wherein said sound reproducing means comprises a pair of acoustic-electric transducers coupled to respective acoustic output ports of said acoustic processing unit for converting said respective sound signals to respective corresponding electrical signals, and
- a pair of electro-acoustic transducers for converting said respective electrical signals to respective corresponding sound signals.
- 6. System according to claim 5, wherein said electro-acoustic transducers are electric headphones.
- 7. System according to claim 5, wherein said electro-acoustic transducers are loudspeakers.
- 8. System according to claim 7, wherein said sound reproducing means further includes a power amplifier for each said loudspeaker, and wherein said power amplifiers and the loudspeakers of said sound reproducing means have a much higher power capability than the electro-acoustic transducers contained in said enclosure.
- 9. System according to claim 1,
- wherein the enclosure of said acoustic processing unit is a walled enclosure having at least first and second spaced-apart openings through one wall thereof to which said acoustic output ports are respectively coupled, and
- wherein each of said electro-acoustic transducers is a loudspeaker having a vibratile diaphragm, and wherein at least a first and a second of said loudspeakers are supported on said one wall each with its diaphragm over a respective opening.
- 10. System according to claim 9,
- wherein said enclosure has an even number of spaced-apart openings through said one wall,
- wherein a like even number of loudspeakers are supported on said one wall each with its diaphragm covering a respective one of said openings, and
- wherein said acoustic transmission means comprises a first group of acoustic transmission paths for coupling sound waves from half of said openings to a first acoustic output port, and a second group of acoustic transmission paths for coupling sound waves from the other half of said openings to the other acoustic output port.
- 11. System according to claim 10,
- wherein said one wall has length and width dimensions and said openings are substantially uniformly spaced along the length dimension, and
- wherein the acoustic transmission paths of said first group are coupled to alternate odd ones of said openings, and the acoustic transmission paths of said second group are coupled to alternate even ones of said openings.
- 12. System according to claim 1,
- wherein said enclosure has an internal baffle disposed substantially parallel to and spaced from said one wall dividing the volume defined by said enclosure into a first chamber enclosing said at least first and second electro-acoustic transducers and a second chamber, and wherein said acoustic processing unit further comprises:
- at least one additional electro-acoustic transducer mounted on said baffle within said second chamber each connected to receive an electro-acoustic signal from another different one of said channels and each operative, when energized, to radiate sound waves into said first chamber for mechanically inducing substantially corresponding vibrations in the transducers supported in said first chamber.
- 13. System according to claim 12,
- wherein said at least one additional electro-acoustic transducer is a loudspeaker having a vibratile diaphragm, and is supported in an opening in said baffle substantially equidistant from the ends thereof with its diaphragm facing said first chamber, and connected to receive electroacoustic signals from the bass channel of said electronic musical instrument.
- 14. System according to claim 13,
- wherein a plurality of electro-acoustic transducers are supported in respective spaced-apart openings in said baffle and each connected to receive an electro-acoustic signal from a different one of said channels and each operative, when energized, to radiate sound waves into said first chamber.
- 15. System according to claim 12,
- wherein said baffle has an opening therethrough for providing a port between said first and second chambers.
- 16. System according to claim 13,
- wherein said second chamber is ported to the ambient for improving the efficiency of said at least one additional loudspeaker.
- 17. An acoustic processing unit for producing first and second composite acoustic signals from at least first and second electro-acoustic signals, said processing unit comprising:
- a box-like substantially sealed enclosure having at least first and second openings in a wall thereof,
- acoustic transmission means defining first and second separate acoustic output ports acoustically coupled to said first and second openings,
- at least first and second electro-acoustic transducers mounted within said enclosure over said at least first and second openings, respectively, for converting said electro-acoustic signals to corresponding acoustic signals and supplying acoustic power only to respective ones of said acoustic output ports and so arranged relative to each other that an energized transducer mechanically induces substantially corresponding vibrations in the other transducers, and
- means for supplying first and second different electrical signals to said at least first and second transducers, respectively.
- 18. Acoustic processing unit according to claim 17,
- wherein said enclosure is a rectangular box having said openings in one wall thereof, and
- wherein each of said transducers is a loudspeaker having a vibratile diaphragm supported on said one wall with its diaphragm confronting a respective opening.
- 19. Acoustic processing unit according to claim 18,
- wherein said enclosure has an even number greater than two of spaced-apart openings in said one wall,
- wherein a like even number of loudspeakers are supported on said wall each with its diaphragm confronting a different one of said openings and so arranged relative to each other that each energized loudspeaker mechanically induces substantially corresponding vibrations in the other loudspeakers, and
- wherein said acoustic transmission means comprises a first group of hollow tubes for acoustically coupling sound waves from half of said openings to a first of said acoustic output ports, and a second group of hollow tubes for acoustically coupling sound waves from the other half of said openings to the second of said acoustic output ports.
- 20. Acoustic processing unit for producing first and second composite acoustic signals from a plurality of electro-acoustic signals, said processing unit comprising:
- a substantially sealed enclosure having at least first and second openings in a wall thereof,
- acoustic transmission means defining a pair of separate acoustic output ports acoustically coupled to said first and second openings,
- at least first and second electro-acoustic tranducers mounted within said enclosure over said at least first and second openings, respectively, for converting applied electro-acoustic signals to corresponding acoustic signals and supplying acoustic power only to respective ones of said acoustic output ports and so arranged relative to each other that an energized transducer mechanically induces substantially corresponding vibrations in the other transducers,
- an internal baffle dividing the volume defined by said enclosure into a first chamber enclosing said at least first and second transducers and a second chamber,
- at least one additional electro-acoustic transducer mounted on said baffle within said second chamber each connected to receive a different electrical signal and each operative, when energized, to radiate sound waves into said first chamber for mechanically inducing substantially corresponding vibrations in the transducers mounted in said first chamber, and
- means for supplying first, second and third different electro-acoustic signals to said at least first, second and one additional transducers, respectively.
- 21. A system for reproducing at least first, second and third electro-acoustic signals each corresponding to a respective channel, comprising:
- a substantially sealed enclosure having at least first and second spaced-apart openings in a wall thereof;
- at least first, second and third electro-acoustic transducers mounted within said enclosure each connected to receive a different one of said electro-acoustic signals for converting said electro-acoustic signals to respective corresponding acoustic signals, said first and second transducers being supported on said wall over said at least first and second openings, respectively, for supplying acoustic power only to respective ones of said openings and so arranged relative to each that an energized transducer mechanically induces substantially corresponding vibrations in the other of said first and second transducers, and said third transducer is so positioned relative to said first and second transducers that when energized it radiates sound waves for mechanically inducing substantially corresponding vibrations in said first and second transducers,
- means for coupling from said at least first and second openings the acoustic signals radiated by said first and second transducers for deriving first and second composite sound signals each containing different proportions of said acoustic signals, and
- sound reproducing means for reproducing said first and second composite sound signals.
- 22. System according to claim 21, wherein said sound reproducing means comprises first and second acoustic transmission paths for respectively transmitting said first and second composite sound signals directly to the left and right ears of a listener as direct sounds.
- 23. System according to claim 21, wherein said sound reproducing means comprises first and second acoustic-electric transducers for respectively converting said first and second composite sound signals to respective corresponding electrical signals, and
- first and second electro-acoustic transducers for respectively converting said respective electrical signals to respective corresponding sound signals.
- 24. System according to claim 23, wherein said electro-acoustic transducers are stereophonic electric headphones.
- 25. System according to claim 23, wherein said electro-acoustic transducers are loudspeakers.
- 26. Acoustic processing unit according to claim 20,
- wherein said enclosure is a rectangular box having an even number greater than two of spaced-apart openings in said wall,
- wherein a like even number of electro-acoustic transducers are mounted on said wall each over a respective opening, and
- wherein said acoustic transmission means comprises a first group of hollow tubes for acoustically coupling sound waves from half of said openings to a first of said acoustic output ports, and a second group of hollow tubes for acoustically coupling sound waves from the other half of said openings to the second of said acoustic output ports.
- 27. Acoustic processing unit according to claim 20 or 26,
- wherein each transducer mounted within said first chamber is a loudspeaker having a vibratible diaphragm supported on said one wall with its diaphragm confronting a respective opening; and
- wherein each transducer mounted within said second chamber is a loudspeaker having a vibratible diaphragm supported in an opening in said baffle with its diaphragm facing said first chamber.
BACKGROUND OF THE INVENTION
This application is a continuation-in-part of application Ser. No. 72,965 filed Sept. 6, 1979, now abandoned.
This invention relates generally to sound reproducing systems, and more particularly to an acoustic processing system which converts a plurality of electro-acoustic signals to a pair of composite sound signals which may be acoustically transmitted to the right and left ears of the listener, or, alternatively, converted to electro-acoustic signals for reproduction by a pair of electro-acoustic transducers.
Generally, when an electro-acoustic signal from a radio receiver or the like is reproduced by a loudspeaker, sound radiated from the loudspeaker is transmitted directly to the left and right ears of the listener as direct sound and at the same time it is transmitted to the ears of the listener as indirect sound produced by reflection from the walls and floors of a listening room. When such composite sound reaches the ears of the listener, he feels a sound image externally of his head because of the contribution to acoustical distance perception by the indirect sound. However, when the electro-acoustic signal from the radio receiver is reproduced by an earphone, the sound image is localized internally of the head of the listener because no indirect sound is included.
Similarly, when a listener is properly placed with respect to the loudspeakers in a stereo sound reproducing system, sound radiated from both speakers is transmitted to both the left and right ears as direct sound and at the same time sound from both loudspeakers is transmitted to the ears of the listener as indirect sound produced by reflection. However, when the stereophonic signals are reproduced by stereophonic headphones, not only is the indirect sound eliminated, but the left ear hears only the left channel information and the right ear hears only the right channel signal, substantially diminishing the sensation of depth and direction. Actually, the diminution in stereo effect may not always be serious, especially in the case of recorded music, because during recording the microphone (or microphones) utilized to form the left channel would pick up to varying degrees all of the soundwaves in the room, both direct sounds and indirect sounds produced by reflections, and the microphone (or microphones) for the right channel likewise, and by reason of the displacement of the microphones, upon reproduction the ears will detect a depth of field when a stereo headset is used. The microphone array used in originally recording the sound signals has, in essence, pre-processed the signals to allow the listener to hear in a binural reproducing system all of the sounds "heard" by the microphones.
The situation is quite different in an electronic organ, for example, the simplest form of which has at least two channels and a separate loudspeaker for reproducing the electroacoustic signals in each channel. As in the case of stereophonic reproduction, when the organ is played in an open room the left ear hears sound radiated from both speakers (which may be designated left and right) and the left ear likewise hears sound radiated from both the left and right loudspeakers and, additionally, indirect sound produced by reflections from the walls and floors of the listening room are heard by both ears. However, when the electro-acoustic signals are reproduced by a set of headphones, the left ear hears only the sounds that would otherwise be produced by the left loudspeaker and the right ear would hear only the sounds normally produced by the right loudspeaker, which means that, regardless of the fidelity, the listener would not hear the same program that is heard when listening to the loudspeakers. It is one thing to attempt to reproduce the full fidelity of full size loudspeakers in a set of headphones, but it is quite another to emulate the aural interaction of the two-speaker system when it is open into the listening room and the ears can hear both loudspeakers and the indirect sound produced by reflections. There being no recording involved, the signal processing techniques employed in stereophonic recording are not available to preserve any of the depth or other effects of acoustical and aural interaction.
Headphone reproduction of a musical program produced by the more expensive electronic organs, which typically have four to six or more channels and a separate loudspeaker for each, bears little resemblance to the program heard when the loudspeakers radiate sound into a room. With the intention that the organ is to be played into an open room, the electro-acoustic signals selected for reproduction by the individual channels, the relative spacing of the loudspeakers, and the adjustment of component values, are designed to cause it to sound the way the designer wants it to sound to a person listening to it with both ears in an open listening room. For example, there is usually a separate channel for bass pedal notes, and four other channels may carry string sounds and other ensemble effects more realistically to emulate such effects by reason of emanating from four different spatial locations. The problem with attempting to use headphones for reproducing the program produced by such an organ is that the left ear will hear only the channels the designer prescribes for the "left" channel and the right ear will hear only those channels assigned to the "right" channel. This not only involves electrical mixing of signals from two or more channels, which introduces the risk of cancellation and/or undesirable adding of signal components, but introduces the question of which organ channel signals should be combined to form the "left" and "right" signals for the headphones. The decision is subjective at best, and, in any case, what is heard by the listener bears little resemblance to what would be heard in an open room where the sounds from the several channels are mixed acoustically in the volume between the surfaces of the loudspeakers and the ears of the listener.
Apart from the aspect of unsatisfactory earphone reproduction of the electro-acoustic signals from a multichannel musical instrument, in the case of a multichannel electronic organ having three, four, or possibly six or seven acoustic channels, the cost of the reproducing channels is rather high in that each usually has a power capability of about 35 watts and a separate relatively expensive loudspeaker. Equally if not more important is the space required to accommodate the loudspeakers which are usually and desirably built into the console, particularly in the case of organs intended for use in the home. The problem becomes especially acute as organs are designed to have more and more channels--eight to ten would be desirable for a three-manual organ--without an appreciable increase in the size of the console, the dimensions of which are essentially fixed by the length of the keyboard and the intended placement in the home, when it is further considered that the loudspeakers must be judiciously arranged to distribute the sound from all these channels and to prevent undesired cross-coupling between channels, back waves, etc.
A primary object of the present invention is to reduce the cost and space requirements of the acoustic reproducing channels of an electronic keyboard musical instrument.
Another object of the invention is to provide an acoustic processing system for enabling binaural reproduction of a plurality of electroacoustic signals by an acoustic headphone wherein the sound transmitted to the ears of the listener closely simulates the sound image that would be heard in an open room.
Still another object of the present invention is to provide an acoustic processing system for enabling realistic reproduction of a plurality of electro-acoustic signals by an electro-acoustic headphone wherein the sound signals reproduced at the ears of the listener closely simulate the sound image that would be heard if the plural electro-acoustic signals were transduced into an open room.
Briefly, these objects are achieved by providing an acoustic processing unit in which electro-acoustic signals from a multichannel signal source are converted to corresponding acoustic signals which are acoustically mixed to produce two, or a multiple of two, composite sound signals each containing a dominant component corresponding to a different applied electro-acoustic signal and sub-dominant sounds related to the other applied electro-acoustic signals. The acoustic processing unit consists of a substantially sealed box-like enclosure, in which a plurality of electro-acoustic transducers, one for each signal, each of which may be a small loudspeaker, are mounted to provide the necessary acoustic interaction between the sound waves radiated by the respective loudspeakers to produce the described composite sound signals at a pair of acoustic output ports. More particularly, the loudspeakers are arranged within the enclosure such that pressure variations within the closed air volume due to the vibrations of the diaphragm of each energized speaker mechanically induce sound-producing vibrations in the diaphragms of the others such that each radiates a composite sound wave containing a dominant sound wave corresponding to its applied electro-acoustic signal and sub-dominant sound waves corresponding to the mechanically-induced vibrations of its diaphragm. In essence, the enclosure may be thought of as a miniature room in which a plurality of electro-acoustic signals are acoustically reproduced and acoustically mixed.
For the binaural reproduction of the plurality of electro-acoustic signals in an acoustic headphone, a pair of acoustic transmission paths each including a sound-transmitting earpiece are coupled to the enclosure of the acoustic processing unit for coupling the said two composite sound signals, or two selected combinations of two or more each of said composite sound signals, to the right and left ears, respectively of the listener.
Alternatively, the pair of composite sound signals produced at the acoustic output ports are converted to a pair of corresponding composite electro-acoustic signals for reproduction by a pair of electro-acoustic transducers, such as an electrical headphone or a pair of loudspeakers. In the latter case, by using the described acoustic mixing and reduction of the multichannel signals to two composite sound signals means that multiple amplifier channels are still required, but each channel is much less costly and much smaller in size in that very small inexpensive speakers requiring no more than a few milliwatts of power per channel are used in the acoustic processing unit, which can be supplied by inexpensive integrated circuit amplifiers. Only the two reproducing channels utilized to acoustically reproduce the pair of composite electro-acoustic signals require high power amplifiers and large, relatively expensive loudspeakers.
US Referenced Citations (4)
Foreign Referenced Citations (1)
| Number |
Date |
Country |
| 53-12301 |
Feb 1978 |
JPX |
Continuation in Parts (1)
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Number |
Date |
Country |
| Parent |
72965 |
Sep 1979 |
|
Patent Grant
4347405
