Oscillations, Waves, and Interactions - GWDG

6 M. R. Schroeder, D. Guicking and U. Kaatze
impulse response of a room using so-called maximum-length sequences constructed
from the theory of finite number fields [17].
The room-acoustic tradition of the institute lives on in the acoustic consultancies
of former students (Akustikbüro Göttingen).
3 Speech and hearing
When Manfred Schroeder, who had worked at Bell Telephone Laboratories since
1954, succeeded Erwin Meyer as director, some of the speech research pursued at Bell
was transplanted to Göttingen in 1969. Much of the speech research at Göttingen
involved the application of measuring methods from physics to the human speaking
process. The work included speech synthesis [18,19], prosody [20], speech and speaker
recognition [21,22], speaker-specific vocal-tract parameters [23] and used advanced
mathematical methods, such as neural networks and hidden-Markov processes.
Impedance measurement of the lips and the glottis [24] were performed. Another
goal was the deduction of the area function and of articulatory parameters from
acoustic data, such as the speech signal [25,26], from lip photography and X-rays.
The cross-fertilisation between speech and hearing research is exemplified by the
investigation of the cocktail-party processors by H. W. Strube et al. [27]. Also modulation-frequency
filtering was applied [28]. For fundamental reasons, and in view of the
importance of human hearing for the proper encoding of speech and music signals,
extensive studies of perceptual masking of one sound by another were undertaken [29].
This research was led by Birger Kollmeier and Armin Kohlrausch. A considerable
amount of the work was concerned with the design of better hearing aids [30] and
tests of speech intelligibility for hearing-impaired listeners.
The work on speech compression was based on linear predictive coding (LPC). In
1976, Atal, Hall and Schroeder introduced “perceptual coding” to acoustic signals
resulting in high-quality speech at very low bit-rates, essential for cell phones and
Internet applications.
Some of the ongoing work in speech is aimed at improving diagnostic tools for
voice pathologies (in collaboration with professor E. Kruse, see the contribution in
this book [31]). Hearing research is still a field of interest of B. Kollmeier at the
University of Oldenburg and A. Kohlrausch at Philips Research, Eindhoven [32].
4 Noise control
In the early 1980s, research projects on active impedance control were started with
controllers in analog electronics, both for air-borne sound and structural vibrations
[33,34]. Besides several smaller projects, active broadband noise control in cars was
investigated in collaboration with an automobile manufacturer, applying adaptive
digital feedforward control with fast algorithms to cope with nonstationary tyre
rolling noise, and with varying acoustic transfer functions [35]. As a demonstration
object, low-frequency fan noise of a kitchen exhaust was cancelled successfully [36];
a presentation at the Hanover fair 1995 found vivid interest. A major research field