- The films were made in the angiography lab of the Lund University Hospital, with the permission of the faculty of medicine and the valued and generous assistance of the staff of the Roentgen Technology Section.
- Each informant was limited to one reel of 35mm film, which ran for about 40 seconds at 75 frames/second.
- A highly unidirectional microphone placed close to the subject’s mouth reduced the background noise level recorded from the rotating anode of the X-ray generator and the camera shutter. A sound treated booth was not available. The background noise level was subsequently reduced by inverse-filtering the recordings, using a digital filter created from the spectrum of the background noise.
- The camera delivered a synchronizing pulse which appeared as a dot in the corner of every tenth frame. These pulses were also recorded synchronously with the speech signal on a parallel track after transposition to 6 kHz to avoid the lower frequency region of the speech spectrum. Spectrograms were subsequently made after mixing and balancing the speech and pulse signals. It was then possible to identify the speech spectrum corresponding to any film frame.
- A copper wire with blobs of solder at 10mm intervals was taped to each informant’s head and nose in the mid-sagittal plane to provide a scale for life-size reproduction of the image.
- A radio-opaque paste was applied to the midline of the tongue and lips.
- Each informant’s head was steadied against a small rest.
- The camera shutter speed was 75 frames/second (one exposure every 13.3 milliseconds). The radiation was pulsed with one 3 millisecond burst to each frame. Fine grain 35mm negative cine film was used (Fuji X-ray ciné film FS). Positive copies were made for viewing and anlysis (Gevaert S 99).
- The informants wore a protective apron and the radiation was coned down to protect the eyes and the thyroid gland.
- The estimated exposure and dose for each reel of film was as follows (anode voltage 120 kV, cathode current 64 mA, 4 mm aluminium and i mm copper filters, focus-skin distance 1200mm, field 100x100mm, 3200 frames/reel):
- Exposure at the image intensifier: 15mr/frame, 50r/reel
- Exposure at the skin: 230 mr/reel
- Absorbed dose: 60-200 mrad/reel
- Gonad dose: negligible
- Bone marrow dose: negligible
© Sidney Wood and SWPhonetics, 1994-2012