WO1995035012A1

WO1995035012A1 - The recording and reproduction of waver patterns

Info

Publication number: WO1995035012A1
Application number: PCT/CA1995/000336
Authority: WO
Inventors: Eric Saretzky
Original assignee: Eric Saretzky
Priority date: 1994-06-13
Filing date: 1995-06-13
Publication date: 1995-12-21
Also published as: AU2876195A

Abstract

This invention provides for the recording of a pattern of perceptible waves, the recording itself, and the reproduction of the pattern to provide a convincing three-dimensional image. The waves are, in particular, sound waves. The invention is primarily based on the principle of reversibility. Thus, the waves emanating from a complex source are sensed by sensors at a number of positions and separately recorded. These recorded signals are then reproduced and waves generated at locations which mimic the positions of the sensors, thereby recreating the pattern of waves. Preferably, at least four sensors are used, and they are located at spaced positions to define a volume of space between them, so that the recorded signals incorporate three-dimensional information. Similarly, wave generators that are used to generate the waves are located at spaced positions to define a volume of space between them. The sensors and the wave generators may have directional characteristics, which are suitably arranged in a corresponding manner. Signals supplied by the sensors may be recorded in a digital, sequential manner.

Description

THE RECORDING 7AND REPRODUCTION OF WAVER PATTERNS

THIS INVENTION relates generally to the recording and reproduction of a pattern of waves.

More particularly, the invention relates to a method of and apparatus for recording a pattern of waves,* a recording of such a pattern,* and a method of and apparatus for supplying the pattern of waves.

According to a first aspect of the invention, there is provided an apparatus for supplying a pattern of perceptible waves, which includes a reproducing means for reproducing recorded signals to provide at least three separate drive signals, which represent the values of the perceptible waves at different particular positions in a previously existing pattern of the waves,* and at least three wave generator means, there being an equal number of wave generator means as there were earlier positions and with the locations of the wave generator means mimicking the earlier positions, each wave generator means being responsive to an appropriate drive signal.

Further according to the first aspect of the invention, there is provided a method of supplying a pattern of perceptible waves, which includes

SUBSTITUTESHEET reproducing recorded signals to provide at lease three separate drive signals, which represent the values of the perceptible waves at different particular positions in a previously existing pattern of the waves; applying each of the drive signals to respective wave generator means, there being an equal number of wave generator means as there were earlier positions and with the location of the wave generator means mimicking the earlier positions; and generating a perceptible wave by each wave generator means to reproduce the pattern of waves.

According to a second aspect of the invention there is provided a recording of a pattern of perceptible waves, which includes a carrier on which are recorded at least three separate drive signals representative of varying values of the waves at different particular positions in a previously existing pattern.

According to a third aspect of the invention there is provided an apparatus for recording a pattern of perceptible waves, which includes at least three sensors for sensing the varying values of the waves, which are located at predetermined spaced positions,- and a recording means for recording signals supplied by the sensors which are representative of the varying values sensed by each of the sensors.

Further according to the third aspect of the invention there is provided a method of recording a pattern of perceptible waves, which includes sensing the varying values of the waves at at least three predetermined spaced positions to provide sensed signals representative of the sensed varying values,- and recording the sensed signals.

The waves may be perceptible and may, in particular, be aurally or visually perceptible.

The sensors may be located in a plane. They may actually be located in a plane or they may be positioned in positions which do not, actually, lie in a plane, and the signals are then recorded in such a way that the sensors are effectively located in the plane. If the sensors are in the plane, then the signals supplied by them are recorded without any time delay. If they are not actually in a plane, then they may be recorded with ^'suitable time delays to effectively represent the signals in a plane. If the signals are recorded with a time delay for any particular signal, then such delay is accounted for when the signals are reproduced. Thus, the wave generator means may also be located in a geometric plane if the drive signals supplied to them are synchronised, or they may not be in a geometric plane with the appropriate drive signals having suitable time delays, so that the signals supplied by the wave generator means are what would have been supplied if they had, in fact, been in a geometric plane. Thus, the location of the wave generator means would mimic a geometric plane.

It will be appreciated that, advantageously, there should be a correspondence between the spatial arrangement of the sensors and the spatial arrangement of the corresponding wave generator means. The applicant believes that, preferably, the arrangement of the wave generator means should be substantially the same as that of the sensors.

Thus, the recording may include instructions as to how many wave generator means are required and how they should be arranged. By "instructions", is also meant information in regard to the geometric positioning of the wave generator means.

Those skilled in the art will appreciate that the wave generator means need to be connected to the reproducing means in phase with one another. The sensors may have directional characteristics . The wave generator means may then have similar directional characteristics. Preferably, the wave generator means may then be arranged so that their directional characteristics emulate the arrangement of the directional characteristics of the sensors .

In a particular arrangement, when the sensors and wave generator means are arranged in a plane, their directional axes may be arranged to be perpendicular to the plane which they define.

It will be appreciated further that the sensed signals are preferably recorded in a synchronised manner and synchronising pulses may accordingly be provided. Similarly, the drive signals are preferably reproduced in a synchronised manner.

The pattern of waves may be dynamic.

As indicated above, the waves may, in particular, be aurally perceptible. In this case, the sensors may be microphones and the wave generator means may be loudspeakers.

The varying value sensed at each of the points may be recorded in a digital, sequential manner. The recorded signals may be arranged in groups, with each group representing the sensed signals at the various points at a particular instant in time. Each group may be demarcated by a synchronising signal, which may, most conveniently, be located at the beginning of each group. Further, each group may be divided into a number of sectors, each sector representing the sensed signal at each of the different points. Thus, each sector will represent a different channel . Each sector will then be divided into a suitable number of bits, as is known in the art.

The recorded signals may be encoded in any suitable manner. The signals may be recorded on a single track, or two or more tracks.

The signals may be recorded on any suitable medium.

For example, the signals may be recorded on a magnetic medium such as digital audio tape (DAT) or in an optically readable manner such as on a compact disc

(CD) .

The sensors may provide analogue signals that are then processed to provide a corresponding digital signal . The analogue signals from the various sensors may be processed simultaneously by separate processing devices, to provide the equivalent digital signals. These digital signals are then recorded in a predetermined sequential manner. Similarly, when the pattern of waves is reproduced, the various digital signals may be read from the DAT or CD and supplied to a suitable number of conversion devices for converting the digital signals to equivalent analogue signals.

Instead, the signals may be processed sequentially if the processing speed is fast enough. For example, the signals may be processed at a sampling rate of 50KHz, with a processing speed of lμs. Thus, the signal from a first sensor is sampled at l/_s after a datum point. The signal from the next sensor at a time 3μs after the datum point, and so on.

SHORT DESCRIPTION OF THE DRAWINGS.

Figure 1 is a schematic illustration of a first embodiment of a sound recording apparatus according to the present invention,-

Figure 2 is a schematic illustration of a first embodiment of a sound supply apparatus according to the invention.

Figure 3 shows schematically a second embodiment of an apparatus for recording a pattern of sound waves in accordance with the invention;

Figure 4 shows schematically a second embodiment of an apparatus for supplying the pattern of sound waves recorded by the apparatus shown in Figure 3 ;

Figure 5 shows a variation of part of the apparatus shown in Figure 3 ,-

Figure 6 shows schematically how the various analogue signals supplied by various microphones may be recorded in a digital sequential manner,-

Figure 7 shows schematically how the digital signals are sequentially arranged; and

Figure 8 shows schematically how the digital signals are reproduced.

DESCRIPTION OF EMBODIMENTS

Referring firstly to Figure 1, a tiered orchestral stage 10 is shown, with a number of musicians 12 thereon. In front of the orchestral stage 10 are four microphones A, B, C and D, which are spaced apart from one another in a rectangular configuration in an upright plane. The microphones A and C are supported on a first stand 14, while the microphones B and D are supported on a second stand 16. The plane in which the microphones are arranged extends generally transversely to the stage 10. The musicians 12 comprise a large number of sound sources which each generate dynamically varying sound waves which radiate away from the musicians 12 towards the microphones and towards an audience 18. The individual sound waves interact with each other to provide a dynamically varying pattern of sound waves. It will be appreciated that the manner in which the sound waves interact is extremely complex and the manner in which sound pressure varies (in respect of time) at each point in the three-dimensional space occupied by the audience will be different.

The outputs of the microphones A, B, C and D are fed to a multi-track tape recorder 20, or another recording device which is able to record each of the electrical outputs of the respective microphones on a suitable recording medium in a synchronised manner.

In a prototype installation, the microphones A, B, C and D were Bruel and Kjaerl omni-directional microphones, directed towards the musicians along the Z axis in Figure 1. Microphones A and B, and microphones C and D were positioned approximately 6m apart, in the direction of the X axis. Microphones C and D were positioned approximately 0.85m above the floor, with microphones A and B approximately 2m above microphones C and D, respectively, in the direction of the Y axis.

In tests carried out with the above described installation, recordings were made on four tracks of the tape recorder 20, with the signals from the respective microphones being recorded in phase. Subsequently, the recordings were replayed using the same or a similar tape recorder 20, the four discrete outputs of which were fed via respective two-channel amplifiers 22 and 24 to four loudspeakers A',B' C and D' arranged to correspond to the similarly designated microphones. In the test set-up, the loudspeakers were arranged in a vertical plane, with approximately 2,5m spacing on the X axis between the loudspeakers A' and B' , and C and D' . The loudspeakers A' and B' were positioned approximately 1.58m on the Y axis above the loudspeakers C'and D' , respectively, while the latter were positioned on the floor. Listeners 26 were seated approximately 3m away from the plane of the loudspeakers, on the Z axis. The loudspeakers were Dunlavy #1 speakers.

Listening tests showed clear horizontal and vertical imaging, allowing accurate location of individual instruments both vertically and horizontally. In addition, the reproduction of depth or distance information was considered to be more realistic than conventional stereo (two speaker) systems. This effect was checked by comparing the above described discrete, four channel synchronised recording with two channels of the recording reproduced on two of the horizontally displaced loudspeakers.

Although the above described system requires additional microphones, recording, storage and reproducing channels and loudspeakers, it is technically simple and elegant and produces a convincing three- dimensional virtual sound image of a three-dimensional stage. Whereas a conventional stereo sound reproduction system creates an image along a line (corresponding to the X axis in the drawings) between two loudspeakers, the system of the present invention creates an image in a plane (defined by the X and Y axes) , with virtual depth information on the Z axis being created effectively by interference between the waveforms radiated by the respective loudspeakers.

The present invention is not restricted to the reproduction of sound, but could, for example, be used in the reproduction of three-dimensional visual images, using a number of photosensors and controllable light sources analogously to the microphones and loudspeakers illustrated in Figures 1 and 2.

Referring now to Figure 3, an apparatus for recording a pattern of aurally perceptible waves is designated generally by refernce numeral 110. The pattern of waves is generated by an orchestra comprising a number of musicians 112.

The apparatus 110 comprises eight microphones 114 and an eight track tape recorder 116. The microphones 114 are located at -the corners of an imaginary rectangular box and define a space between them. It will be noted further that the microphones 114 are inwardly directed. Further, it will be noted that the microphones 114.1, 114.2, 114.3 and 114.4 define a first plane and the other microphones 114.5, 114.6, 114.7 and 114.8 define a second plane that is parallel to the first and spaced therefrom. The microphones 114 have a cardioid characteristic with a polar axis. The axes of the microphones extend perpendicularly to the planes.

As seen in Figure 3, the planes are also parallel to the orchestra.

The microphones 114 are mounted on stands 118 and they are connected to the tape recorder 116 by cables 120.

The tape recorder 116 amplifies and records signals received from the microphones 114 on a high quality magnetic tape (indicated schematically by reference numeral 122) supplied from a reel 124. The recorder 116 has eight separate channels, each with its own input connector 126, amplifier 128 and record head (not shown) . As indicated, microphone 114.1 is connected to the input connector 126.1 of the first channel; microphone 114.2 is connected to the input connector 126.2 of the second channel; and so on.

It will accordingly be appreciated that the signals from each microphone 114 are recorded independently, but in a synchronised manner, without any relative time delays. Further, at any one instant in time, the value of the sound wave extant at each position at which a microphone 114 is located is recorded, thereby recording the pattern of the sound waves at that instant . The pattern of sound waves is dynamic and the manner in which it varies is thus recorded.

After a recording session, the tape 122 will have recorded thereon the signals representative of the varying values of the sound waves at the points in the two planes at which the microphones are located, the signals having been recorded separately from each other. The reel 124 on which the tape 122 is wound will have annotated thereon information as to the number of channels and the spatial positioning of the microphones 114.

Referring now to Figure 4, an apparatus for supplying the pattern of waves is designated generally by reference numeral 130. The apparatus 130 comprises eight loudspeakers 132 and an eight channel tape playback machine 134. As seen in Figure 4, the loudspeakers 132 are also positioned at the corners of an imaginary rectangular box to emulate the positions of the recording microphones 114, in accordance with the information supplied with the reel 124. Thus, loudspeaker 132.1 is located at a position which corresponds with that of microphone 114.1; loudspeaker 132.2 is located at a position which corresponds with that of microphone 114.2; and so on. It will be appreciated that the loudspeakers 132 are positioned in two spaced parallel planes in a similar manner to that of the microphones 114.

The loudspeakers 132 also each have a cardioid characteristic that is preferably as close to that of the microphones 114 as possible. The loudspeakers 132 have their polar axes 140 directed perpendicularly to their planes, and pointing inwardly, the same as with the microphones 114.

The loudspeakers 132 are mounted on stands 142.

The machine 134 has eight separate channels with separate pick-up heads (not shown) and independent amplifiers 136. Each amplifier 136 has its own output connector 138, with the loudspeakers 132 being connected to their appropriate output connectors 138.

In use, the machine 134 reproduces the signals recorded on the tape 122 in a synchronised manner. Thus, the signals supplied by the machine 134 to the loudspeakers 132 are an accurate reproduction of the signals picked up by the microphones 114. Thus, the loudspeakers 132 reproduce the dynamic patterns of sound waves emanating from the orchestra.

Referring now to Figure 5, a further arrangement of microphones 150 is shown. It will be seen that the microphones 150.1, 150.2 and 150.3 lie in plane, whereas the microphone 150.4 is out of the plane. If the microphones 150 are being utilised to record sound waves emanating from a source that is located on one side of the plane (for example on the opposite side of the plane to that of the microphone 150.4), then the signals from the microphones 150.1, 150.2 and 150.3 could be recorded with a suitable time delay. This time delay would depend on the distance of the microphone 150.4 from the plane and the speed of travel of the sound waves. With such a time delay, the microphones 150 would be located in an effective plane. When the signals are reproduced, if they were recorded with such a time delay, then they coulά be reproduced by loudspeakers located in a plane without using any corresponding time delay. If the signals are reproduced with a corresponding time delay, then the loudspeakers would have to be positioned in a similar manner to that of the microphones shown in Figure 5.

Those skilled in the art will appreciate that the signals supplied by microphones arranged as shown in Figure 5 could be recorded without any time delay as long as they are reproduced on loudspeakers having a corresponding arrangement.

Referring to Figure 6, an apparatus for recording a pattern of waves, similar to that shown in Figure 3 is shown. The apparatus shown in Figure 6 is referenced in a similar manner to that of Figure 3. The apparatus is thus designated generally by reference numeral 210 and has eight microphones 214.1 to 214.8 that are arranged spatially, as shown in Figure 3. However, with the apparatus shown in Figure 6, eight analogue to digital processing units 260.1 to 260.8 are provided and the tape recorder 216 records signals in a digital manner. The analogue to digital units 260.1 to 260.8 sample analogue signals supplied from the microphones 214 at a sampling rate of 48 KHz and provide twenty bit digital signals. These signals supplied from the analogue to digital units 260.1 to 260.8 are recorded by the recorder 216 on magnetic tape in a sequential manner as is explained below.

Referring now to Figure 7, a portion of the magnetic tape 222 is shown. The digital signals are recorded on the tape 222 in groups, one group 262 being shown. Each group 262 is divided into nine sectors

264.1 to 264.9. A synchronising pulse is recorded in the first sector 264.1. The digital signals supplied by the units 260.1 to 260.8 are stored in a suitable memory that the recorder 216 has, and then supplied sequentially to a record head (not shown) to be sequentially recorded in the sectors 264.2 to 264.9. Thus, the digital signal supplied by unit 260.1 is recorded in sector 264.2; the digital signal from unit

260.2 is recorded in sector 264.3 and so on. The tape 262 is transported at a suitable speed to enable the digital signals to be recorded in a reproducible manner.

Referring now to Figure 8, shown therein is an apparatus for supplying a pattern of waves such as is shown in Figure 4. The apparatus is designated generally by reference numeral 230 and has eight loudspeakers 232.1 to 232.8 which are arranged spatially as shown in Figure 4. The apparatus 230 has a play back machine 234 which is of the digital type so that the signals recorded on the tape 222 can be reproduced. The digital signals recorded in the sectors 264.2 to 264.9 of each group 262 are supplied to eight analogue to digital convertors 266.1 to 266.8. Thus, the signals supplied by the microphone 214.1 are reproduced and supplied to the convertor 266.1; the signals supplied by the microphone 214.2 are supplied to the convertor 266.2 and so on. The convertors 266 convert the digital signals to analogue signals. These signals are then supplied to amplifiers 268.1 to 268.8. These amplifiers then supply suitable signals to the loudspeakers 232.

By means of the invention, dynamic wave patterns may be reproduced with a convincing three-dimensional image.

Claims

1. An apparatus for supplying a pattern of perceptible waves, which includes a reproducing means for reproducing recorded signals to provide at least three separate drive signals, which represent the values of the perceptible waves at different particular positions in a previously existing pattern of the waves,- and at least three wave generator means, there being an equal number of wave generator means as there were earlier positions and with the locations of the wave generator means mimicking the earlier positions, each wave generator means being responsive to an appropriate drive signal.

2. The supply apparatus claimed in Claim 1, in which the reproducing means includes at least three separate amplifying means for amplifying the separate drive signals.

3. The supply apparatus claimed in Claim 1, in which three of the drive signals represent the values of the waves at three different points in an effective plane and three of the wave generator means are located at suitable positions to mimic said plane.

4. The supply apparatus claimed in any one of the preceding claims in which the waves are aurally

, perceptible.

5. The supply apparatus claimed in Claim 2, in which the wave generator means are connected to the amplifying means in phase with one another.

6. The supply apparatus claimed in Claim 1, in which the wave generator means have directional characteristics and the wave generator means are arranged with their directional characteristics directed in a predetermined manner.

7. The supply apparatus claimed in Claim 1, in which the recorded signals comprise digital, sequential signals.

8. The supply apparatus claimed in Claim 1, in which the reproducing means provides at least four separate drive signals, which represent the values of the waves at four different points in space, three of these points defining a plane and the fourth being spaced from said plane,- and the apparatus includes at least four wave generator means, the wave generator means being located in suitable positions to mimic said points.

9. An apparatus for recording a pattern of perceptible waves, which includes at least three sensors for sensing the varying values of the waves, which are located at predetermined spaced positions,- and a recording means for recording signals supplied by the sensors which are representative of the varying values sensed by each of the sensors.

10. The recording apparatus claimed in Claim 9, in which the recording means separately records the signals supplied by the sensors.

11. The recording apparatus claimed in Claim 9, in which three of the sensors are located in an effective plane and the recording means records signals representative of the varying values in said effective plane.

12. The recording apparatus claimed in Claim 9, in which the waves are aurally perceptible.

13. The recording apparatus claimed in Claim 9, in which the sensors have directional characteristics and the sensors are arranged with their directional characteristics directed in a predetermined manner.

14. The recording apparatus claimed in Claim 9, in which the recording means records the signals supplied by the sensors in a digital, sequential manner.

15. The recording apparatus claimed in Claim 9, which includes at least four separate sensors that are located at four separate positions in space, three of which define a plane and the fourth being spaced from said plane.

16. A recording of a pattern of perceptible waves, which includes a carrier on which are recorded at least three separate drive signals representative of varying values of the waves at different particular positions in a previously existing pattern.

17. The recording claimed in Claim 16, in which three of the drive signals represent the values of the waves at three positions which define an effective plane.

18. The recording claimed in Claim 16, in which the waves are aurally perceptible.

19. The recording as claimed in Claim 16, which includes instructions specifying the spatial location of wave generator means when used to reproduce the wave pattern utilising the drive signals.

20. The recording as claimed in Claim 19, in which said instructions also specify the orientation of directional characteristics of the wave generator means.

21. The recording as claimed in Claim 16, in which the drive signals are recorded in a digital, sequential manner.

22. The recording as claimed in Claim 16, in which at least four drive signals are recorded on the carrier which represent the values of the waves at four different points in space, three of these points defining a plane and the fourth being spaced from said plane.

23. A method of supplying a pattern of perceptible waves, which includes reproducing recorded signals to provide at least three separate drive signals, which represent the values of the perceptible waves at different particular positions in a previously existing pattern of the waves,- applying each of the drive signals to respective wave generator means, there being an equal number of wave generator means as there were earlier positions and with the location of the wave generator means mimicking the earlier positions,- and generating a perceptible wave by each wave generator means to reproduce the pattern of waves.

24. The supply method claimed in Claim 23, in which the drive signals are separately amplified.

25. The supply method claimed in Claim 23, in which three of the drive signals represent the values of the waves at three different points in an effective plane and three of the wave generator means are located at suitable positions to mimic said plane.

26. The supply method claimed in any one of Claims 23 to 25, in which the waves are aurally perceptible.

27. The supply method claimed in Claim 24, in which the wave generator means are supplied with amplified drive signals that are in phase with one another.

28. The supply method claimed in Claim 23, in which the wave generator means have directional characteristics and they are arranged with their directional characteristics directed in a predetermined manner.

29. The supply method claimed in Claim 23, in which the recorded signals comprise digital, sequential signals.

30. The supply method claimed in Claim 23, in which at least four separate drive signals are provided which represent the values of the waves at four different points in space, three of these points defining a plane and the fourth being spaced from said plane,- and at least four wave generator means are provided that are located in suitable positions to mimic said points.

31. A method of recording a pattern of perceptible waves, which includes sensing the varying values of the waves at at least three predetermined spaced positions to provide sensed signals representative of the sensed varying values,- and recording the sensed signals.

32. The recording method claimed in Claim 31, in which the sensed signals are separately recorded.

33. The recording method claimed in Claim 31, in which three of the positions are located in an effective plane and the sensed signals that are recorded are representative of the varying values in said effective plane.

34. The recording method claimed in Claim 31, in which the waves are aurally perceptible.

35. The recording method claimed in Claim 31, in which the varying values are sensed by means of sensors that have directional characteristics and the sensors are arranged with their directional characteristics directed in a predetermined manner.

36. The recording method claimed in Claim 31, in which the sensed signals are recorded in a digital, sequential manner.

37. The recording method claimed in Claim 31, in which the varying values at at least four separate points in space are sensed, three of the points defining a plane and the fourth being spaced from the plane.