Ian F. Hunt

Cinematographer and Filmmaker

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Future Cinema – 5.1 Surround Sound

5.1 Surround Sound

A day testing and proving and disproving ideas for recording and playing 5.1 Surround Sound files.

Idea Development – 5.1 Surround Sound

Sennheiser ME66 Microphones - Surround Sound Recording Setup

Sennheiser ME66 Microphones - Surround Sound Recording Setup

I propositioned the idea that if the dummy head complete with the binaural microphones was positioned in a simulated cinema environment and a DVD with a 5.1 Surround Sound soundtrack was played using a surround sound speaker system then recorded using the binaural microphone setup then the surround sound effect would be duplicated in the recording.

5.1 Surround Sound Headphones

5.1 Surround Sound Headphones

Following a number of recording tests this did not seem to be the case, although I suspect the problems of sourcing a true 5.1 Surround Sound System could have contributed to the failure of the test. We did successfully combine the binaural effect with the recording of the films soundtrack by overlaying our own voices into the recording but the 5.1 Surround Sound effect did not truly represent itself when played back through headphones.

However I have a theory that with the application of the right technology the original theory may well prove to be correct, for example it is possible to source 5.1 Surround Sound Headphones where the speakers are actually separated by 12 degrees in the headset.

[youtube.com/watch?v=5QETQNFYnp4]

5.1 Surround Sound

Definition: 5.1 channel sound, also known as Surround Sound, is a standard sound format found on most DVDs and some CDs. The five channels are left and right main speakers (stereo), a center channel for movie dialog and on-screen action, two rear speakers to surround the listener and a .1 channel (pronounced ‘point-one channel’) for bass. The .1 channel is intended for a subwoofer, used for special effects in movies and very deep bass in music. The designation ‘.1’ means that it is not a full range channel and is designed to reproduce only a narrow range of bass tones.

5.1 Channel Sound Definition. Site Accessed 20/11/2011 http://stereos.about.com/od/glossary/g/FivePointOne.htm

Zoom R24 Digital Recorder

Zoom R24 Digital Audio Recorder

Zoom R24 Digital Audio Recorder

For the new recordings we decided to use a Zoom R24 Digital Recorder rather than the Fostek recorders we used in the previous recording sessions. The main advantage to using the Zoom R24 was that it could record more than 2 channels of audio simultaneously in fact it can record 8 tracks in all, which saved us from having to synchronise 2 recording devices as we had previously. The Audio tracks were also saved onto a SD card making it much easier to import the data to the Logic Pro application.

Initially the Zoom was powered from the mains supply and Phantom power used to power the microphones, but we were getting a power hum on all the audio recordings. To cure this we had to power both the recorder and microphones using batteries. I suspected at the time that as we were in a studio using a dimmable lighting system, either the power from the lighting racks was effecting the main supply or the neutral had  high frequency noise running on it or it was not pegged at earth potential and was floating several volts above zero. As we had no means of checking this and this being outside of the brief, switching to battery power was the only option.

Logic Pro

In the afternoon session we utilised a new software application called Logic Pro and attempted to create a 5.1 Surround Sound soundtrack using the sound files recorded previously in the studio see previous blog Future Cinema – Binaural Sound – Digital Sound Recording. Each track was assigned a channel 1 to 4 representing Left Front, Right Front and Left Back, Right Back.

Logic Pro Application Screenshot

Logic Pro Application Screenshot

The microphones used to record the original tracks was centrally located, the resulting soundtrack appeared to have good separation but not necessarily 5.1 Surround Sound. Personally I felt that this might be due to the fact that the recordings were of only one sound source, centrally located and so the sound when played back should have been heard equally from all 4 speakers which was the case. If instead on just using one sound source, we had recorded multiple sound sources across the studio space we would have been able to have identified these different sound sources and their locations when played back. For example four members of the group each stand beside a microphone and announce their location that is; Left Front, Right Front, Left Back and Right Back, a simple idea but not thought of at the time.

Audacity 1.3.13-beta!

Audacity 1.3.13-beta screenshot

Audacity 1.3.13-beta screenshot

The beta version of this popular Sound Editing Application according to my research now supports AC3 file formats which allows you to save sound files with up to 6 channels. For our purposes this would allow us to create a 5.1 Surround Sound file with the option of a Sub-woofer channel.

Unfortunately although it is now possible to  be able to create these file formats we still have to find a 5.1 Surround System to be able to play them back.

The AC3 file type is primarily associated with ‘AC3 Audio File Format’ by Dolby Laboratories.

AC3 is a 6-channel, audio file format by Dolby Laboratories that usually accompanies DVD viewing. It operates 5 channels for normal range speakers (20 to 20,000 Hz) and the 6th channel reserved for low-frequency (20 to 120Hz) sub-woofer operation.

Human’s audible range of frequency is typically between 20Hz to 20kHz (that’s 20,000Hz) and this range is called sonic. Anything below the range is referred to as infrasonic whilst anything above is ultrasonic.

FileExt – Website Accessed 21/10/2011. http://filext.com/file-extension/AC3

Next Steps

The next step is to revisit the studio space and finalise the full soundtrack, that is the 5.1 surround sound and the binaural sound simultaneously and then go back to the Logic Pro application and assign a track to each channel and experiment to see how the 2 sound sources can be integrated for playback in a cinematic environment.

Future Cinema – Links to Related Blog Entries

  1. Future Cinema – Project Conclusion
  2. Future Cinema – Sound Effects
  3. Future Cinema – Digital Cinema
  4. Future Cinema – 5.1 Surround Sound
  5. Future Cinema – Binaural Sound – Digital Sound Recording
  6. Future Cinema – 360 Degree Camera Mount
  7. Future Cinema – Learning Agreement (Updated)
  8. Future Cinema – Audio / Film Script 1st Draft
  9. Future Cinema – Binaural Sound Recording
  10. Future Cinema – The Film Pitch
  11. Future Cinema – does it have one?

 

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