Friday, 28 February 2020 12:19

New Mosca release coming soon

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A new version of the software Mosca will shortly be released, implementing work by Thibaud Keller. The release will bring support for new ambisonic libraries as well as VBAP, OSC support and integration with OSSIA-score, improved GUI, support for higher order ambisonic signals, banks of RIRs selectable on a per-source basis and many other improvements. For details on the upcoming release, see the conference paper by Iain Mott and Thibaud Keller: Three-dimensional sound design with Mosca. See also https://escuta.org/mosca.

Wednesday, 06 December 2017 18:08

Mosca Video Tutorial

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Tutorial on using the GUI interface of the Mosca quark for SuperCollider. Please listen with headphones and please view in full-screen mode.

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Friday, 12 May 2017 19:04

Botanica

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Botanica is a garden-based sound art project by Iain Mott. Members of the public, together with a guide, don headphones and shoulder-bag and explore an immersive sound composition overlaid on the landscape. The sounds heard are largely confected from nature and involve audio recordings from the cerrado of Brazil’s central west. As participants walk through the garden, their movements are tracked by GPS and this allows them to hear a variety of sounds mapped to different locations. The overlapping soundscapes encountered are 3-dimensional and head-tracking on the headphones helps to deliver a interactive immersion responsive to the finest movements of the listener. Sounds may be fixed in space, acting like beacons, or may follow their own trajectory through the garden. The headphones are of an open type, allowing the natural sounds of the environment to blend with those of the overlay.

Botanica is presented as a sonic fantasy. It is inspired by landscape, the biosphere and the elements and is returned to the environment in a form to be explored in a specific setting, the garden, another fantasy of and for nature. It is a sound composition organised in space rather than time and as such interacts directly with the environment and with human presence.

Since the early 1990s, sound artist Iain Mott (UK/AU) has been engaged in the spatial mapping of sound in various contexts. His 1998 work Sound Mapping made with engineer Jim Sosnin and designer Marc Raszewski is particularly relevant to the current project. Among the very first artworks to use GPS,  Sound Mapping was selected for exhibition in the prestigious Prix Ars Electronica of the same year in Linz, Austria.  For the past decade Mott has lived in Brazil where he is regular collaborator with actress Simone Reis and currently a lecturer in voice and sound design at the Departamento de Artes Cênicas (Theatre Arts Department) of the University of Brasilia. Botanica is an outcome of his research in the field of ambisonics (a form a surround sound first developed in the UK in the 1970s) and specifically the project Ambisonic Cerrado which involves the use of ambisonic field recordings of the cerrado in theatrical contexts. His open source computer software Mosca (an ambisonic extension class to the SuperCollider music language) was created in the research and will form the technical basis of Botanica.

This audio demonstration of Mosca involves the spatialisation of mono, stereo and B-format material. As well as using music and B-format recordings made by Iain Mott, it also contains 3 B-format recording by John Leonard of geese, a Chinook helicopter and of the Stanbrook Abbey Choir. These recording by John are presented here with kind permission. Other recorded sounds include those of monks in the Luohan Temple in Chongqing, China, frogs in São Jorge, Goiás in Brazil, a matchbox and an original recording of Sputnik 1 made by Roy Welch, reproduced with Roy's permission.

Please listen with headphones and ensure that the left and right channels are positioned correctly.

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Saturday, 29 October 2016 12:32

Ambisonic Map

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Ambisonic map with high quality B-format field recordings for download (48kHz, 24bit in wav format). Each record is accompanied by UHJ stereo and binaural mixes for direct listening online. The map was produced as part of the Ambisonic Cerrado project.

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Sunday, 11 September 2016 11:37

B-Format to Binaural & UHJ Stereo

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Use the three scripts contained in the zip file below in "Download attachments" to batch convert a directory of B-format audio to binaural and UHJ stereo. Requires that SuperCollider is installed with the standard plugins and that the "Ctk" quark is enabled. The main shell script also encodes mp3 versions of the binaural and UHJ files and if this feature is used (not commented out), the system will require that "lame" is installed. The SuperCollider script uses the ATK and is adapted directly from the SynthDef and NRT examples for ATK.

Unzip the scripts in a directory, edit the paths to match your installation and distribution of Linux in the file renderbinauralUHJ.sh, make this file executable and run in the directory containing the b-format files to perform the conversions. 

Mono source with local and global reverberation. Binaural decoding performed with the CIPIC HRTF database's subject ID# 21, included in the ATK.

Please listen with headphones and ensure that they are correctly orientated. 

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Sunday, 11 September 2016 08:09

Making Impulse Responses with Aliki

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The following procedure shows how to make B-format impulse responses (IRs) with the Linux software Aliki by Fons Adriaensen. A detailed user manual is available for Aliki, however the guide presented here in escuta.org is intended to show how to produce IRs without the need to run the software in the field and enables the use of portable audio recorders recorders such as the Tascam DR-680. The procedure was arrived upon through email correspondence with Fons. His utility "bform2ald" is included here with permission.

Field Equipment used:

  • Zoom H4n - for sine sweep playback
  • Core Sound Tetramic, stand and cabling
  • Tascam DR-680 multi-channel recorder
  • Yorkville YSM1p powered audio monitor with cabling to play Zoom H4n output
  • 12V sealed lead acid battery and recharging unit
  • Power inverter to suit monitor

1. Launch Aliki in the directory in which you wish to create and store your "session" files and sub-directories, select the "Sweep" window and create a sweep file with these or other values:

  • rate: 48000
  • fade in: 0.1
  • start freq: 20
  • Sweep time: 10
  • End freq: 20e3
  • Fade out: 0.03

2. Select "Load" to load the sweep into Aliki and perform an export as a 24bit wav file or file type of your choosing.

3. Import the "*-F.wav" export in Ardour or other sound editor and insert an 800Hz blip or other audio marker 5 seconds before start. Insert some silence before the blip as some players (the Zoom H4n for example) may miss some initial milliseconds of files on playback. Export file as stereo 24bit 48kHz stereo file since the Zoom doesn't accept mono files.

4. Import file into Zoom H4n recorder for playback.

5. In the field, connect line out of Zoom H4n to Yorkville YSM1p and play file, recording with tetramic and Tascam DR-680. In my first test I recorded with the meter reading at around -16dB. Could have given the amp more gain, but the speaker casing was beginning to buzz with the low frequencies.

6. The Tascam creates 4 mono files. Use script to convert to A-format and with Tetrafile to convert to B-format with the mic's calibration data (with "def" setting). 

7. Install and use the utility bform2ald (see "Download attachments" below) to convert the B-format capture to Aliki's native "ald" file format.

8. Load the "ald" sweep capture into Aliki. Enter into edit mode and right-click to place a marker at the beginning of the blip. Use the logarithmic display to make the positioning easier. Once positioned, left-click "Time ref" to zero the location of the blip, then slide the marker to the 5 second mark and again left-click "Time ref" to zero the location of the start of the capture.

9. Right-click a second time a little to the right of the blue start marker. This will create a second olive coloured marker, marking the point at which a raised cosine fade-in starting at the blue marker will reach unity gain. When positioned, left-click "Trim start". Zoom out and drag the two markers to the end of the capture in order to perform a fade out in the same way with "Trim end". Use the log view to aid with this process. 

10. Save this trimmed capture in the edited directory with "Save section".

11. Select "Cancel" and then "Load" to reload the freshly trimmed capture in the edited directory, then select "Convol". In this window, select the original sweep file used to create the capture in the "Sweep" dialogue. Enter "0" in the "Start time" field and in the "End time" field enter a number in seconds that represents the expected reverberation time plus two or three more seconds. Finally, select apply to perform the deconvolution, then perform a "Save section" to save the complete IR in the "impresp" directory.

12. Select "Cancel" and "Load" to load the recently created impulse in the "impresp" directory, then enter edit mode. The impulse may not be visible so use the zoom tools and in Log view, identify the first peak in the IR which should appear shortly after 0 seconds. This peak should represent the direct sound. While we may decide not to keep this peak, we will use it now to normalise the IR so that a 0 dB post fader aux send to the convolver will reproduce the correct ratio of direct sound to reverberation when using "tail IRs" or IRs without the direct impulse (see 13 below). To normalise, right-click to position the blue marker on the peak then left-click "Time-ref" to zero the very start of the direct impulse and shift-click "Gain / Norm". 

13. The complete IR created above in step 12, containing the impulse of the direct signal as well as those of the first reflections and of the diffuse tail, may be convolved with an anechoic source to position that source in the sound field. If used in this way, the "dry" signal of the source should not be mixed with the "wet" or convolved signal and there will be no control over the degree of reverberation. If however the first 10msec of the IR are silenced (using the blue and olive markers and "Trim start" in Aliki to fade in from silence just before 10msec, for example), the anechoic signal may be positioned in the sound field by including the dry signal in the mix (panned by abisonic means to a position corresponding to that of the original source in the IR) and varying the gain on the "wet" or convolved signal to adjust the level or reverberation and reinforce the apparent position of the virtual source through first reflections encoded in the IR. Another alternative is to silence the first 120msec of the IR to create a so-called "tail IR". This removes the 1st reflections information entirely from the IR and enables the sound to be moved freely by ambisonic panning. The level of reverberation is adjustable however the will be no 1st reflections information to aid in the listener's localisation of the virtual source or to contribute to the illusion of its "naturalness". A fourth possibility is to use a tail IR in conjunction with various IRs for different locations. These IRs encoding first reflections only, those occurring between 10 and 120msec, could be chosen for example to match the positions of specific musicians on a stage. The engineer will first pan the dry signal of a source in a particular position, then mix in the wet signal derived from convolution with the 1st reflections IR for the corresponding location and additionally send a feed from the dry signal to a global tail IR common to all sources.

A binaural demonstration of the Mosca SuperCollider class using the voice of Simone Reis reciting from the drama Gota d'Água, B-format recordings of a Chinook helicopter and of Spitfires by John Leonard, B-format recordings of insects and frogs from Brasilia and Chapada dos Veadeiros, a galloping horse (spatialised mono source with Doppler effect and Chowning-style reverberation) and some Schubert (stereo). Binaural decoding performed with the CIPIC HRTF database's subject ID# 21, included in the ATK.

Please listen with headphones and ensure that they are correctly orientated

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