A View from Dresden onto the History of Speech Communication
Part 6: Measuring speech respiration
The respiratory behaviour of humans provides important bio-signals, in speech communication we are interested in respiration while speaking. The investigation of speech respiration mainly entails the observation of i) activity of muscles relevant for in- and exhalation, ii) lung volume, iii) airflow, iv) sub-glottal air pressure, and v) kinematic movements of the thorax and the abdomen.
In the “early days” of experimental phonetics the measurements were mainly focused on lung volume and the kinematic behaviour of the rib cage and the belly. We present here three devices that are also part of the historic acoustic-phonetic collection (HAPS) which will be re-opened during the International Workshop on the History of Speech Communication Research.
The Atemvolumenmesser (Figure 1) is an instrument to measure the vital capacity of the lung and the phonatory flow, respectively. The human subject maximally inhales with the help of a mask put onto mouth and nose. The subsequent expelling air arrives into the bellows via a mouthpiece and a rubber tube. The resulting volume can be seen on a vertical scale. A stylus that is mounted on a small tube at the scale allows to register the temporal dynamics of speech breathing with the help of a kymograph.
Figure 2 shows a Gürtel-Pneumograph (“belt-pneumograph”) which serves to investigate the respiratory movements. The wave-like surfaced rubber tubes are fixed around the upper part of the body of the human subject in order to measure the thoracic and abdominal respiration. Changes of the kinematics result in changes of the air pressure to be transmitted via tubes of so-called Marey capsules onto the stylus to be registered with a kymograph.
The kymograph was the core instrument of the experimental phonetic research until the 1930s. The ‘wave-writer’ graphically represents changes over time. A revolving drum was wrapped with a sheet of paper with soot (impure carbon) on the surface and a fine-grained stylus easily writes the measured changes.
A clockwork motor was responsible for the constant revolution of the drum. Time-relevant parameters like speech wave forms, air pressure changes of the pneumograph or air volume changes of the Atemvolumenmesser were transduced into kinematic parameters via the Marey capsules and registered on the time axis.
The drum in Figure 3 has a height of 180 mm and circumference of 500 mm. At the beginning the drum is at the top and sinks continuously downwards during the registration process. This spiral movement allows the graphical recording of longer curves on the paper. The speed of the revolution of the drum could be set between 0.1 and 250 mm per second.
Jürgen Trouvain and Dieter Mehnert
Photographs Copyright TU Dresden / HAPS