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Denoising of ambisonic field recordings

2016-01-11

Screen_shot_2016-01-11_at_15

I’ve been experimenting lately with what might be the best way to do noise reduction (denoising) of ambisonic field recordings. In some of the recordings from very quiet locations preramp noise is noticeable. I’m not interested in reducing any of the background noise that is part of the recorded ambience itself, I just want to reduce the amount of hiss introduced in the process of recording.

The recordings are done using a SoundField SPS200 mic and a SoundDevice 788T recorder. The resulting recordings are A-format, and I use the SoundField SPS200 plugin to convert the A-format recordings to B-format. Denoising is done using iZotope RX. RX4 is not able to deal with multichannel files, so I have to split the 4-channel recording into two stereo tracks, do noise cancellation on them, and then merge back into four channels again. However there are at least three different approaches to this:

  1. Treat the original A-format recordings, and afterwards convert the processed files to B-format using the SPS200 plug.
  2. Treat the converted B-format recordings.
  3. Decode the B-format files to A-format using the BtoA decoder from Ambisonic Toolkit for Reaper, remove noise, merge, and then re-encode to B-format using the ATK AtoB encoder.

I have done recordings of the SoundDevice at various input levels with no mic connected. The resulting hiss is very similar to the noise that I want to remove, and I use these recordings to train the Denoiser. The resulting curves are stored as a set of presets.

After having experimented over several days, and a lot of useful input from the sursound list, it seems to me that processing of the B-format signals alter some of the spatial information. The resulting spatial image appears to me to be more unstable, and less spatially articulated. If the Denoiser algorithm do alter phase I suspect that it might also impact the original A-format recordings negatively. So I am ending up with the last option above.

One benefit of this is that I can do it all in Reaper, and I don’t have to manually split and merge sound files. It is still a laborious process: At my 4 year old laptop rendering is happening at 1.1 x realtime speed, so there is a lot of waiting.

This blog post was done while waiting for a rendering that took close to 50 minutes to complete. Duh!

Ambisonic Toolkit in the wild

2016-01-04

Vr-gorilla1

One of the nice things about developing open-source software is seeing where it ends up being used. When ambisonics gets used in advertisements for wild gorilla preservation lodges in Uganda, it’s clearly becoming accessible beyond the electro-acoustic music camp.

The Amsterdam-based Spook.fm music and audio production company has made SpookSync3D, a utiity for syncing view direction and play information between the 360 video player Kolor Eyes and Reaper ambisonic projects using Ambisonic Toolkit for Reaper. The above video gives a clear and thorough presentation of the workflow when designing ambisonic sound for 360 virtual reality using Reraper and Ambisonic Toolkit.

Spook.fm has collaborated on several projects with VR Gorilla, another Amsterdam based studio specialising in virtual reality production. One of the projects they have worked on, the Virtual Gorilla app for Android, is available in the Google Play Store.

Happy New Year - Happy New Studio

2016-01-02

Studio

One of the things I love about the Christmas holiday is that I am often able to set a few days aside for larger tasks that I don’t manage to find the time for during the rest of the year. This often serves as long-term investments, efforts that do not address an imminent deadline, and that do not necessarily pay of immediately. It might be reading up on topics, developing or learning new software, or something else.

This year I have been revamping my studio. The sound absorbers that have been laying around for years are finally up on the walls, and I have set up a 12 speaker 3D ambisonics rig. I still have some calibration to do before I am all set to go, but this definitively feels good.

ATK for Reaper presentation at Ircam

2015-12-15

Two weeks ago I did a presentation of Ambisonic Toolkit (ATK) for REAPER at the IRCAM forum. The video is now online. It gives an introduction to first-order ambisonics and the creative workflow that these plugins invite.

Atmospherics goes Luftskipet

2015-11-30

Søkjer_-_heim_1_web

Me and Jeremy Welsh participate in the exhibition “Søkjar : heim”. The exhibition takes place at Luftskipet, located at Straume nearby the Sartor shopping center. The exhibition opens Tuesday December 1st at 19:00, and runs until December 13. It is curated by Håkon Holm-Olsen, Gro Lygre Petersen and Linda Soh Trengereid, and features artists with an affiliation to Sotra. One of the particularities of this exhibition is that all the works have been donated. The audience can apply to get one of the works, and the applications will be reviewed by the curators. So, our video piece is up for grabs!

Søkjar_heim

Installation view – video and slick speakers.

Me and Jeremy present a single-channel video originating from the ongoing Atmospherics project. This version was first presented at an Avgarde concert last spring, and is dedicated to the late Morten Eide Pedersen, former composition teacher at the Grieg Academy.

Download the program for the exhibition

 

Søkjer : Heim
1. – 13. desember 2015 i Luftskipet på Straume

Vernissasje: Tirsdag 1. desember kl 19.00
Adresse: Tyttebærbrekko 4 5353 Straume

Tre kunstnere fra Sotra ville gi hjemstedet sitt en litt annerledes kunstutstilling. Se for deg dette: du kommer inn på en utstilling. Rundt deg kan du se malerier, tegninger, skulpturer, grafikk og du kan høre lyd fra en installasjon og mennesker som prater, skåler og hilser på kjente. Du går en runde i rommet. Alle de 8 verkene i utstillingen er laget av profesjonelle kunstnere med tilknytning til Sotra, stedet du selv bor, eller har reist til for å se denne utstillingen. Ved inngangen i rommet står det en postkasse. Ved siden av postkassen ligger det en bunke med papir. Ordene på papiret forteller deg at det er et søknadsskjema. Nå, se for deg dette: du har like stor sjanse som alle de andre feststemte menneskene rundt deg til å eie hvilke som helst av kunstverkene i rommet. Arbeidene som er utstilt koster ikke penger, men tiden din. Skjemaet ved postkassen vil vite hvorfor akkurat du fortjener arbeidet til en av de deltakende kunstnerne. Du går en runde til i rommet.

Sammen med 5 andre kunstnere inviterer vi, Gro Lygre Petersen, Håkon Holm-Olsen og Linda Soh Trengereid til en kunstutstilling i Luftskipet på Straume. Vi ville gjøre et kunstprosjekt på vårt hjemsted som tar for seg kjøpepresset som preger vår tid. Et prosjekt i periferien der kunst får være kunst på sine egne premisser uten å bli styrt av krefter som vanligvis trekker i økonomiske tråder. Ved å gi bort alle kunstverkene i utstillingen gir vi alle i publikum en lik sjanse til å bli eier av et verk, uavhengig av bakgrunn, alder eller økonomisk situasjon. For å ha muligheten til å få et arbeid må man levere en søknad som argumenterer for hvorfor vi skal gi verket til henne eller ham. En søknadssituasjon som gjenspeiler en del av hverdagen til mange av kunstnerne i ustillingen.

Når pengene er tatt bort, hva er da igjen i relasjonen mellom kunst og publikum?

Kunstnerne som viser arbeid er; Kari Bugge Gjerstad, Odd Gjerstad, Trond Lossius/J_eremy Welsh, Heidi Kårtveit, Geir Opdal, Håkon Holm­-Olsen, Linda Soh Trengereid og Gro Lygre Petersen. Det vises verk i mange uttrykk; skulptur, lydverk, maleri, tegning og grafikk og alderen på kunstnerne varierer fra 31 til 90 år.

Den lokale jury, som etter søknadsfristen vil avgjøre hvem som får hvilket verk, godtar søknader på nynorsk, bokmål og engelsk. Det er ingen øvre eller nedre aldersgrense for å søke.

Utstillingen er støttet av Billedkunstnernes Vederlagsfond, BKK, Haltenbanken, Sotra Bruk, Fjell Kommune og Bodoni.

 
 
 

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