Trough sounds of various kinds and origins, trough space and time, thanks to the theatre of our minds, we are able to see everything in much better way than with overrated sense of vision. Just plug in your headphones, sit back and relax. The journey to magical world of sounds of ambient starts here…
I’ve started Soundography in early 2009 as the transition from photography as the method to capture moments I care about. As I developed my knowledge and constant craving for new sounds, I moved project to the next level.
Today, Soundography combines mixes in binural mode for real 3D experience when consuming trough headphones.
Binaural Library is currently not accessible on-line. You can enjoy some of resources on the Sondography blog
Second stage of the project is to create representation of space using Ambisonic setup.
Ambisonics is a method of recording information about a soundfield and reproducing it over some form of loudspeaker array so as to produce the impression of hearing a true three dimensional sound image. I deliberately say “impression” to stress the fact that if you truly wished to reproduce the soundfield present in a two metre sphere up to say 20 kHz then you can argue from information theory that you would need many, many channels and loudspeakers. Estimates of the number have varied from 400,000 upwards! In practise, all you can actually do is to determine how much information we can capture with some sensible combination of microphones and then to find some way of using that information to fool the ear into hearing a full soundfield.
Attempts to provide directional information in artificially reproduced sound images started in the late nineteenth century when a “broadcast” of a concert was made in France using multiple telephones spaced along the front of the stage, transmitting over wires to a similar number of telephone receivers. Quality was, of course, rather poor but an impression of direction was undoubtedly gained.
In the late 1920′s and early 1930′s a more formal basis for directional reproduction was laid down by Alan Blumlein in Britain and the RCA company in the States. The techniques they developed were for systems using only a small number of channels of information for reproduction over a pair of loudspeakers.
The technique developed by Alan Blumlein consisted of a pair of microphones with figure of eight characteristics, mounted as close together as possible and with the front lobe of one mic pointing 45 degrees to the left of the front-back line and the front lobe of the other pointing 45 degrees to the right. Although this does provide excellent stereo imagining it does have a problem. Because of the figure of eight characteristics sounds coming from the rear are also picked up and when reproduced over a pair of loudspeakers these sounds are folded over and mapped onto the front soundstage. This results in a sound which is too reveberant for many ears.
“Purist” recording engineers who like the simplicity and accuracy of the Blumlein technique have modified it in order to remove this perceived problem. By replacing the figure of eight microphones with ones with cardioid characteristics and changing the angle between them so that it just includes the desired soundstage, it is possible to use the cardioid mic’s lack of response to rearward sounds to reduce the mapping of rear reveberant sounds onto the front reproduced soundstage. This results in a much more acceptable if less accurate sound image. (As a matter of practice the angle between the mics should not be more than about 120 degrees or less than 90).
It does, however, seem a pity to throw away this information when we already have insufficient. The dummy head technique can be employed to utilise this lost information although only for headphone listening. (Work has been done and is still being done to get better results over loudspeakers for dummy head recordings but problems still remain to be solved). By using some form of analogue of the human head with microphones picking up sound where the ears should effectively be and then reproducing these signals over headphones very good results can be obtained with sounds appearing to come from all directions, not just the front. Unfortunately, the best results with the most stable images come from a dummy head which closely matches the listeners. However, the more closely the head matches that of any one listener, the worse the results may get with other listeners. Even if you try to generate some kind of average head you can come unstuck. One set of recordings I heard a few years ago, which were made using a head based on several years of painstaking measurements of all the colleagues and students of a Continental European researcher, gave absolutely stable and very precise results except for the fact that to me and all the other British people who listened to it, the front and back directions were transposed. The BBC approach where the head is just disk of perspex with microphones placed a few centimetres either side of it gives a more universally acceptable result at the expense of true precision.
Ambisonics, on the other hand, goes back to the original ideas of Alan Blumlein and builds on them. By just adding an omnidirectional microphone to the pair of figure eight units it can be shown that you can capture ALL the information that it is possible, with such simple low order microphones, to capture about the horizontal soundfield at that point. It is, of course, assumed that you have arranged to have the capsules TRULY coincident, that is all three capsules are acoustically at exactly the same place in the soundfield. This impossibility becomes even more difficult when you add an up-down oriented figure eight capsule in order to record height information as well. This problem has been overcome in the Soundfield microphone which uses four small capsules situated on the surface of a notional sphere to sample the incoming sounds. By some clever mathematics it is possible to generate the signals which would have been given by our four truly coincident capsules-at least up to some reasonably high frequency. (It should be noted that in Ambisonics the horizontal figure eight units are mounted front-back and side-to-side rather than at 45 degrees).
Having got the information recorded in this form, the task of producing the illusion has to be accomplished. This is completely separate from the task of capturing the information in the first place and is based on an amalgam of various theories of hearing covering both low (below 700 Hz) and high frequency mechanisms. The decoder must be adjustable for different speaker layouts.
The question must be posed ‘How does this approach differ from the Quadraphonic systems?. Quadraphonics-or more properly Quadrifontal-systems were based on a very simple theory. If mono sound systems can be regarded as a hole in a concert hall wall and stereo systems as two holes AND are better then four holes MUST be better still. Unfortunately this is simply untrue since the extra information carried is partially redundant and causes considerable confusion and instability in the perceived images, particularly along the sides.
Extensive listening tests over many years show Ambisonic recordings to be at least as good as any other form of recording at capturing sound images and far better than most, but what is its applications in electro-acoustic music? To understand these we need to look at some basic theory on Ambisonics.
BASIC AMBISONIC TECHNOLOGY
The Ambisonic surround sound system is essentially a two part technological solution to the problems of encoding sound directions (and amplitudes) and reproducing them over practical loudspeaker systems in such a way as to fool the ears of listeners into thinking that they are hearing the original sounds correctly located. This can take place over a 360 degree horizontal only soundstage (pantophonic systems) or over the full sphere (periphonic systems). Systems using the so-called ‘B’ format signals to carry the recorded information require three and four channels respectively for full encoding of sounds to the kind of accuracy achievable with first order microphones (cardioid, figure eight etc.). Reproduction requires four or more loudspeakers depending on whether it is pantophonic or periphonic, size of area etc. Practical minimums are four for horizontal only, eight if you require height as well. The important thing to note is that there is no need to consider the actual details of the reproduction system when doing the original recording or synthesis, since if the B format specifications are followed and suitable loudspeaker/decoder setups are used then all will be well. In all other respects the two parts of the system, encoding and decoding, are completely separate.
read more
Trough sounds of various kinds and origins, trough space and time, thanks to the theatre of our minds, we are able to see everything in much better way than with overrated sense of vision. Just plug in your headphones, sit back and relax. The journey to magical world of sounds of ambient starts here...
I've started Soundography in early 2009 as the transition from photography as the method to capture moments I care about. As I developed my knowledge and constant craving for new sounds, I moved project to the next level.
Today, Soundography combines mixes in binural mode for real 3D experience when consuming trough headphones.
Binaural Library is currently not accessible on-line. You can enjoy some of resources on the Sondography blog
Second stage of the project is to create representation of space using Ambisonic setup.
Ambisonics is a method of recording information about a soundfield and reproducing it over some form of loudspeaker array so as to produce the impression of hearing a true three dimensional sound image. I deliberately say "impression" to stress the fact that if you truly wished to reproduce the soundfield present in a two metre sphere up to say 20 kHz then you can argue from information theory that you would need many, many channels and loudspeakers. Estimates of the number have varied from 400,000 upwards! In practise, all you can actually do is to determine how much information we can capture with some sensible combination of microphones and then to find some way of using that information to fool the ear into hearing a full soundfield.
Attempts to provide directional information in artificially reproduced sound images started in the late nineteenth century when a "broadcast" of a concert was made in France using multiple telephones spaced along the front of the stage, transmitting over wires to a similar number of telephone receivers. Quality was, of course, rather poor but an impression of direction was undoubtedly gained.
In the late 1920's and early 1930's a more formal basis for directional reproduction was laid down by Alan Blumlein in Britain and the RCA company in the States. The techniques they developed were for systems using only a small number of channels of information for reproduction over a pair of loudspeakers.
The technique developed by Alan Blumlein consisted of a pair of microphones with figure of eight characteristics, mounted as close together as possible and with the front lobe of one mic pointing 45 degrees to the left of the front-back line and the front lobe of the other pointing 45 degrees to the right. Although this does provide excellent stereo imagining it does have a problem. Because of the figure of eight characteristics sounds coming from the rear are also picked up and when reproduced over a pair of loudspeakers these sounds are folded over and mapped onto the front soundstage. This results in a sound which is too reveberant for many ears.
"Purist" recording engineers who like the simplicity and accuracy of the Blumlein technique have modified it in order to remove this perceived problem. By replacing the figure of eight microphones with ones with cardioid characteristics and changing the angle between them so that it just includes the desired soundstage, it is possible to use the cardioid mic's lack of response to rearward sounds to reduce the mapping of rear reveberant sounds onto the front reproduced soundstage. This results in a much more acceptable if less accurate sound image. (As a matter of practice the angle between the mics should not be more than about 120 degrees or less than 90).
It does, however, seem a pity to throw away this information when we already have insufficient. The dummy head technique can be employed to utilise this lost information although only for headphone listening. (Work has been done and is still being done to get better results over loudspeakers for dummy head recordings but problems still remain to be solved). By using some form of analogue of the human head with microphones picking up sound where the ears should effectively be and then reproducing these signals over headphones very good results can be obtained with sounds appearing to come from all directions, not just the front. Unfortunately, the best results with the most stable images come from a dummy head which closely matches the listeners. However, the more closely the head matches that of any one listener, the worse the results may get with other listeners. Even if you try to generate some kind of average head you can come unstuck. One set of recordings I heard a few years ago, which were made using a head based on several years of painstaking measurements of all the colleagues and students of a Continental European researcher, gave absolutely stable and very precise results except for the fact that to me and all the other British people who listened to it, the front and back directions were transposed. The BBC approach where the head is just disk of perspex with microphones placed a few centimetres either side of it gives a more universally acceptable result at the expense of true precision.
Ambisonics, on the other hand, goes back to the original ideas of Alan Blumlein and builds on them. By just adding an omnidirectional microphone to the pair of figure eight units it can be shown that you can capture ALL the information that it is possible, with such simple low order microphones, to capture about the horizontal soundfield at that point. It is, of course, assumed that you have arranged to have the capsules TRULY coincident, that is all three capsules are acoustically at exactly the same place in the soundfield. This impossibility becomes even more difficult when you add an up-down oriented figure eight capsule in order to record height information as well. This problem has been overcome in the Soundfield microphone which uses four small capsules situated on the surface of a notional sphere to sample the incoming sounds. By some clever mathematics it is possible to generate the signals which would have been given by our four truly coincident capsules-at least up to some reasonably high frequency. (It should be noted that in Ambisonics the horizontal figure eight units are mounted front-back and side-to-side rather than at 45 degrees).
Having got the information recorded in this form, the task of producing the illusion has to be accomplished. This is completely separate from the task of capturing the information in the first place and is based on an amalgam of various theories of hearing covering both low (below 700 Hz) and high frequency mechanisms. The decoder must be adjustable for different speaker layouts.
The question must be posed 'How does this approach differ from the Quadraphonic systems?. Quadraphonics-or more properly Quadrifontal-systems were based on a very simple theory. If mono sound systems can be regarded as a hole in a concert hall wall and stereo systems as two holes AND are better then four holes MUST be better still. Unfortunately this is simply untrue since the extra information carried is partially redundant and causes considerable confusion and instability in the perceived images, particularly along the sides.
Extensive listening tests over many years show Ambisonic recordings to be at least as good as any other form of recording at capturing sound images and far better than most, but what is its applications in electro-acoustic music? To understand these we need to look at some basic theory on Ambisonics.
BASIC AMBISONIC TECHNOLOGY
The Ambisonic surround sound system is essentially a two part technological solution to the problems of encoding sound directions (and amplitudes) and reproducing them over practical loudspeaker systems in such a way as to fool the ears of listeners into thinking that they are hearing the original sounds correctly located. This can take place over a 360 degree horizontal only soundstage (pantophonic systems) or over the full sphere (periphonic systems). Systems using the so-called 'B' format signals to carry the recorded information require three and four channels respectively for full encoding of sounds to the kind of accuracy achievable with first order microphones (cardioid, figure eight etc.). Reproduction requires four or more loudspeakers depending on whether it is pantophonic or periphonic, size of area etc. Practical minimums are four for horizontal only, eight if you require height as well. The important thing to note is that there is no need to consider the actual details of the reproduction system when doing the original recording or synthesis, since if the B format specifications are followed and suitable loudspeaker/decoder setups are used then all will be well. In all other respects the two parts of the system, encoding and decoding, are completely separate.
read more
Ambisonics is a method of recording information about a soundfield and reproducing it over some form of loudspeaker array so as to produce the impression of hearing a true three dimensional sound image. I deliberately say “impression” to stress the fact that if you truly wished to reproduce the soundfield present in a two metre sphere up to say 20 kHz then you can argue from information theory that you would need many, many channels and loudspeakers. Estimates of the number have varied from 400,000 upwards! In practise, all you can actually do is to determine how much information we can capture with some sensible combination of microphones and then to find some way of using that information to fool the ear into hearing a full soundfield.
Leave your response!