Speech Recordings in Standardized Setting
The recordings are carried out in an acoustically shielded laboratory, thus guaranteeing
a reproducible setting and the acoustic conditions required for a dynamic range of
60 decibel (dB). Speech signals are digitized online with a sampling rate of 48 kHz
at a 20 bit resolution. Test person and technician are situated in two different rooms,
separated from each other by an acoustically shielded window. In cases where no
acoustically shielded laboratory is available, a "quiet" room with sufficiently low
background noise is used.
Experimental Setting
A recording encompasses "counting out loud from 1 to 40" and "reading a standard text out
loud". The test persons are led to the recording studio where they are asked to feel
comfortable, to relax, and to count loud from 1 to 40 in their native dialect and with their
normal voice. This speech signal is used by the technician to calibrate the recording, and
the measurement may be repeated several times if necessary. The microphone distance should
be kept constant and should be approximately 50 cm.
Signal Calibration
The recording is calibrated by the technician in such a way that the maximal signal is
between -2dB and -0dB on the peak meter. Important: the signal amplitude must not exceed
0dB (red LEDs should not light up on the peak meter) in order to avoid clipping. After
voice calibration, a well-defined tone of 5 seconds duration is generated and recorded on
tape for calibration purposes. Under the assumption that counting and chatting with the
technician has helped the test person to relax, the actual measurement is carried out while
the test person is alone in the recording studio. The recording comprises two experimental
conditions "automatic speech" (counting) and "reading a standard text out loud". This design
eliminates all sources of variation due to different content of recorded text, or due to
direct interactions between an interviewer and the test person. Variations due to circadian
fluctuations can be avoided by always recording test persons at a fixed time span in the
morning, for example, beween 8 and 11 o'clock.
Standard Recording Scheme
Speech recordings are carried out according to the following scheme: (1) The test person
is asked to count out loud again from 1 to 40; (2) Short pause of maximal 30 seconds; (3)
The test person is asked to read the standard text out loud; (4) Short pause of maximal 30
seconds; (5) The test person is asked to count out loud again from 1 to 40. The entire
recording procedure takes approximately 15 minutes including volume calibration.
Technical Specifications
Data are stored on a DAT cassette tape recorder TASCAM DA-30 MkII (TEAC Professional
Divison) that has been modified through a high resolution A/D-D/A analogue-digital
converter ADD 30 (LAKE PEOPLE). The sampling rate is 48 kHz, the quantization 20 bit
linear, and the frequency response 20-20,000 Hz +0.1 dB. The microphone MKH 40 P48 U-3
(SENNHEISER) has been specifically selected on the basis of its empirically determined
frequency response curve in order to meet the high linearity of 0.1 dB over the
frequency range 64 Hz - 16kHz.