High-speed photography is the science of taking very fast pictures. It records fast-moving objects as a photographic images onto a storage medium, often digital. After recording, the stored images can be played back in slow-motion.
A normal motion picture is filmed and played back at 24 frames per second, while television uses 25-30 frames. High-speed film cameras can film up to a quarter of a million frames per second by running the film over a rotating prism or mirror instead of using a shutter, thus reducing the need for stopping and starting the film behind a shutter which would tear the film stock at such speeds. Using this technique one can stretch one second to more than ten minutes of playback time (super slow motion).
High-speed cameras are frequently used in science in order to characterize events which happen too fast for traditional film speeds, i.e. the vocal folds vibrations.
In December 2012 Julian McGlashan and Cathrine Sadolin performed an endoscopy/high speed study at CVI in Copenhagen. We recorded 9 singers using highspeed technology. Each singer was examined using an high-speed digital camera:
- Photron Fastcam MH4
– 512X256 resolution
– Captures 8s B&W footage
– 4G Internal memory, download via USB 3
- 300W Xenon light
- Rigid laryngoscope
- Simultaneous Acoustic and ELG recordings
Laryngograph electrodes were positioned over the thyroid cartilages and an omnidirectional microphone placed at distance from the singer which allowed recordings at all levels of loudness. Also the ELG and acoustic signals were captured and analysed with the Speech Studio (Laryngograph) software program.
The longest high speed recording we made lasted 3-4 seconds and it takes around 17 minutes to play back.
High speed of Overdrive with Distortion and Rattle
Here you see a highspeed videoclip of a male singer singing with distortion in Overdrive. The singers starts in Overdrive and then add and remove the distortion and rattle.
Notice the progressive narrowing of the supra glottis structure with Overdrive. The front and the back of the laryngeal opening approach each other, making the opening of the larynx more narrowed and the cuneiforms are rolled in even more than in Curbing.
Also notice the laryngeal gestures for distortion. Again you can see the additional narrowing with the distortion, and especially the false cords coming in and are vibrating, creating the distortion. Also there is medial- lateral constriction of the false folds and an anterior-posterior narrowing and the larynx is slightly raised.
The Rattle is produced by vibration of the cuneiforms or mucosa over the cartilages, either freely or against the epiglottis. Again there was evidence on endoscopy or from the Laryngograph of periodic vocal fold vibration.
Combined effects can be done safely.
Notice that the waveform of the vocal mode is maintained during the distortion and rattle. This indicates that the vibrations of the vocal folds are unhindered and unaffected by the distortion and rattle. So the vocal folds are vibrating freely under the distortion and rattle. This makes sense because the we know that the distortion and rattle is taking place higher in the vocal tract and not on the 1st level (the level of the vocal folds).
In all the examples where we can see the vocal folds, or look at the laryngograph trace, there seems to be a resonably regular pattern, and there didn’t appear to be any evidence of the effect (or any additional noises) being produced in the vocal fold level.
There was evidence on endoscopy or from the Laryngograph of periodic vocal fold vibration.
This information comes from a study effects with the title ‘Can vocal effects such as distortion, growling, rattle and grunting and be produced without traumatising the vocal folds?’. This study was presented by Julian McGlashan at PEVOC7 conference in Groningen, Netherlands, 2007.
This study with the title ‘Analysis of the mechanism of effects such as Distortion, Growl, Grunt and Rattle used in a healthy way by 18 professional singers’. was presented by Cathrine Sadolin at Pevoc 10 (Pan-European Voice Conference) Prague, Czeck Republic, August, 2013.