Oscillations, Waves, and Interactions - GWDG

26 H. W. Strube
3 Acoustic analysis of pathologic voices, extended to running speech 1
3.1 Introduction
For diagnostics and treatment of voice disorders the evaluation of voice quality is
essential. Apart from the auditive judgment by the phoniatrist, it is desirable to find
objective criteria for the rating of voice disorders, especially, to determine physical
quantities appropriate for diagnostic description and classification of speech pathologies.
For this purpose, acoustic analysis methods have been developed. Starting
from known quantities, such as jitter, shimmer, and measures of additive noise, novel
quantities were investigated that allow a better separation of noise from glottal periodicity
disturbances. According to clinical usage, first stationary vowels were considered.
But an analysis of running speech is also desirable, in order to assess the
voice under more realistic conditions. So an important goal of the project was the
extension of the methods to running speech.
Further, in phoniatric diagnostics stroboscopic video recordings of the vibrating
glottis are usual. These were supplemented by high-speed recordings, and automatic
methods of image segmentation were developed (e. g., determination of the glottal
opening area). Besides all this, an extensive data bank with acoustic and optical
recordings as well as diagnostic findings was built up.
3.2 Equipment and data bank
For recording and processing, standard PCs were used with good sound cards (e. g.,
Soundblaster PCI 128) under Linux in an ethernet LAN. The voice recordings were
done in an anechoic and insulated recording room, not containing any noisy devices.
The microphone, a Beyerdynamic HEM 191.15 with spherical characteristic, was
head-fixed about 10 cm in front of the chin. A special graphic interface for recording,
cutting and marking of the voice recordings was programmed.
Presently there are about 77000 voice recordings as WAV files with 48 kHz sampling
frequency: vowels [ε: a: e: i: o: u:] with pitches normal, low, high; running
speech (phonetically balanced standard texts “Nordwind und Sonne” [north wind
and sun] and “Buttergeschichte” [butter story]); spontaneous speech. For archiving
and automatic administration of the voice and video recordings as well as the medical
diagnoses (about 70 different ones), a large MySQL data base was built up. It runs
with a PHP web frontend on a Linux PC, is connected to the patient information
system SAP of the university hospital and has an interface to the video stroboscopy
workplaces. For each patient-related voice analysis, a PDF file with color print can
be generated.
3.3 The Göttinger Hoarseness Diagram
Especially fruitful was the voice characterization by the “Göttinger Hoarseness Diagram”
(GHD) [11–14], Fig. 1. It is based on traditionally important quantities in
phoniatric diagnostics: on one hand, irregularity measures of glottal oscillation, such
1 extended and updated from earlier German papers [9,10]