Digital Signal Processing and System Theory

We present a comprehensive study of a magnetic sensor system that benefits from a new technique to substantially increase the magnetoelastic coupling of surface acoustic waves (SAW). The device uses shear horizontal acoustic surface waves that are guided by a fused silica layer with an amorphous magnetostrictive FeCoSiB thin film on top. The velocity of these so-called Love waves follows the magnetoelastically-induced changes of the shear modulus according to the magnetic field present. The SAW sensor is operated in a delay line configuration at approximately 150 MHz and translates the magnetic field to a time delay and a related phase shift. The fundamentals of this sensor concept are motivated by magnetic and mechanical simulations. They are experimentally verified using customized low-noise readout electronics. With an extremely low magnetic noise level of ≈100 pT/[Formula: see text], a bandwidth of 50 kHz and a dynamic range of 120 dB, this magnetic field sensor system shows out...

Impaired sit-to-stand and stand-to-sit movements (postural transitions, PTs) in patients with Parkinson's disease (PD) and older adults (OA) are associated with risk of falling and reduced quality of life. Inertial measurement units (IMUs, also called "wearables") are powerful tools to monitor PT kinematics. The purpose of this study was to develop and validate an algorithm, based on a single IMU positioned at the lower back, for PT detection and description in the above-mentioned groups in a home-like environment. Four PD patients (two with dyskinesia) and one OA served as algorithm training group, and 21 PD patients (16 without and 5 with dyskinesia) and 11 OA served as test group. All wore an IMU on the lower back and were videotaped while performing everyday activities for 90-180 min in a non-standardized home-like environment. Accelerometer and gyroscope signals were analyzed using discrete wavelet transformation (DWT), a six degrees-of-freedom (DOF) fusion algori...

Hands-free telephone sets with adaptive echo cancellers need an adaptive loss control in order to guarantee a loss of acoustic echo of about 45 dB (ITU-T Recommendation G.167 (l)). The quality of the speech transmission de- pends on the coupling between the echo canceller and the loss control. In this contribution we present an imple- mentation of a hands-free telephone algorithm, using a low-cost fixed-point DSP which is well suited for integra- tion in consumer devices. It is a well known fact that in realistic environ- ments one cannot achieve, even with the best avail- able DSP's, an echo loss of more than 2&25dB with an adaptive echo canceller. This is due to changes in the echo path, disturbing background noise, limited number of filter taps etc. In order to provide a constant total echo loss of about 45dB, one can use an adaptive loss control. An adaptive loss control estimates whether the local speaker or the far-end speaker is talking and attenu- ates the channel that ...

Recently, magnetoelectric sensors have gained importance in medical applications. Among several sensor types microelectromechanical magnetic field sensors are a promising option since they can be manufactured in a very small fashion and can operate at room temperature. In this contribution we present a new readout scheme for such sensors that simultaneously uses amplitude and phase information of a multitude of mechanical modes of a single sensor. The sensors are based on the delta-E effect. All extracted information is optimally combined in order to get a sensor output signal with maximum signal-to-noise ratio (SNR). First measurements have shown very promising results.

The Lombard effect is a phenomenon of increasing the vocal effort that people develop due to, amongst others, the presence of background noise. For example, if the background noise level rises, pitch, loudness of the phone usually increase, but also the duration of phonemes and the diction may change. In order to investigate this effect in any imaginable noise scenario within a soundproof room, a reproducible and easily changeable acoustic ambiance simulation has been developed and is presented in this paper. This noise simulation uses loudspeakers instead of closed headphones which is the common approach. This increases the realism of the noise scenario for the subject and consequently also the ecological validity of the Lombard speech recordings. To remove the simulated noise from the recordings of the subject’s microphone, multi-channel signal processing has been implemented to achieve the same speech quality as with a common headset-based noise simulation.

In this contribution an introduction to bandwidth extension of telephony speech is given. Bandwidth extension in this context means the estimation of the frequency parts that have either been suppressed or canceled out by the transmission over a public telephone network. It is presented why current telephone networks apply a limiting bandpass, what kind of bandpass is used and what can be done to (re)increase the bandwidth on the receiver side without changing the transmission system. These bandwidth extension methods represent a cheap way to increase the quality of non-wideband connections and could even increase the quality of wideband connections. The presented algorithms are based on the source-filter model for the speech production process. Therefore we can split the algorithms into two seperate tasks: