Homework: Radio Play

  • Out: Oct 26, 2021 Tuesday
  • Due: Nov 9, 2021 Tuesday

Objective

Compose a short musical radio play (1~2 min.) consisting of sounds spatialized into four channels which can be listened to binaurally via your web page.

Key Results

  1. Record monophonic audio files with an audio editor.
  2. Use Ambisonic Recorder to spatialize your audio files and download the result.
  3. Compose the files into a final file using a Chuck script which will position the spatialized files in time with respect to each other.
  4. Create a web project that plays the produced file. Start with the starter project if needed.
  5. Upload the project to a new homework directory named hw2 on your CCRMA web space.

Background

Binaural recording uses stereo mics pointed outwards from inside your ears to capture as closely as possible the exact sound pressure waves entering your ear canals. A binaural radio play produced by the BBC, The Revenge (use headphones to listen to it!), demonstrates the possibilities. The binaural technique captures filter (transfer function) differences caused by body parts shadowing and reflecting sounds arriving from various directions: the ear flaps (pinnae), head, shoulders, etc. Played back over headphones or earbuds, binaural preserves the interaural loudness difference (ILD) and interaural time difference (ITD) cues which are basic to sound localization.

Early work in binaural recording was accompanied by predictions that its superior imaging would create a world where everyone would eventually listen through headphones. Playing binaurally-encoded sounds over stereo loudspeakers doesn't result in either good binaural or good stereo and that's one thing holding back wider use. For a position paper, see Jens Blauert's AES Heyser Lecture. He makes a provocative case for binaural as a part of an increasingly realistic synthetic world.

One artist whose work leverages the medium is Janet Cardiff. She composes site-specific 3D audio narratives with spine-tingling interplay of real and phantom presences binaurally-produced. She and her collaborator created a stunning work, Alter Bahnhof Video Walk (select the video page - use headphones), which opens up the possibilities of what you might expect to compose with mobile devices. The composition led participants through the station, each directed by a mobile phone which they were holding while watching with a pre-recorded self-guided tour. You'd turn a corner and someone would be there musicking in the space (convincingly, so you could point to them) only they weren't there then, but at some other point in time, past, alternative present, or future.

Composition

Consideration

You can make this a purely literal radio play - with the constituent tracks all recorded using a microphone and a focus on dialogue and the more literal elements of a play (for example, closing doors).

  • A play using your voice for each of the parts or having some friends join to record.
  • A recitation or speech accompanied by sound effects.

However, you could also 'music-ify' it so that it's something less literal or is more focused on music:

  • A conversation between Peter Pan and Tinkerbell, where Tinkerbell is a sound/melody you play or synthesize - perhaps she flies around in the sound space.
  • Simulating a rehearsal, where a director/conductor takes the center of the sound stage from one side, and rehearses a couple of instruments on different sides of the stage.

Requirements

  1. Record and Spatialize: The work starts with recording 4 monophonic sound sources (4 monaural audio files) and spatializing them.

    • Equip yourself with a digital audio editor, for example, audiomass which runs in the browser or the audacity application or an editor of your own choosing.
    • Learn to -- record from your audio interface and microphone -- load .wav files from your local file system -- save your work as a .wav file (in mono or stereo) at 48kHz sample rate -- edit segments with select, time move, cut, copy, paste -- (optionally) mix multiple tracks, apply reverb and filter.
    • Practice recording and playback using your audio interface, mic and headphones rather than using the computer's built-in mic and speakers). Make sure the analog input gain and output volume levels are well-adjusted to avoid noise or clipping.
    • Record and export 4 different monaural files into the same local directory on your local computer (come up with a simple naming scheme, like "test1.wav", "test2.wav", ...).
    • Re-record the tracks adding spatial movement using the Ambisonic Recorder.
    • Open your tracks directory with "Choose Files" and multiple select all 4 files -- test "Play / Pause" with the four buttons at the bottom -- practice moving sounds around -- select "Room Size" = "Huge" and select "Wall Material" = "Marble" -- reload the page if you want to start from scratch.
    • For the assigment, pick a sound from your tracks directory and choose the acoustical space you need for it -- click "Record", click the sound's "Play" button and start moving it -- when done, click the sound's "Stop" button, Right-click on the save text and then "Save Link As" -- check that there's a new binaural stereo file where you intended and load it into your audio editor and check that it's ok.

  2. Temporal Layout and Layering: The radio play should have a total duration of a couple minutes or so. The Chuck portion of the project will do the final assembly. A Chuck script will read in your spatialized files and combine them into one output file.

    • Install Chuck.
    • Test it by copying demo0.ck into a local file and running the command chuck demo0.ck in a terminal. Try out some more examples.
    • Customize. Specify a sequence of clips to finalize the entire radio play. Running the chuck script will produce a .wav file which you can link to the button in index.html.