Real-Time Simulation of Underwater Channels

Real-time Simulation of Underwater Channels


	Contents:
	Overview
	MIMO Systems
	Speech and Data Communication
	Underwater Channel Simulation
	SONAR Sisters

Todays research interests in underwater communication and navigation are continuously growing. However, testing of new systems involves a lot of eﬀort and costs. Due to this fact it is often useful to develop a complex simulation environment. The ﬁrst aspect of the underwater channel simulation is closely related to the questions:

What happens with an acoustic signal if it propagates through the water?
And what kind of transformations are resulting from this?

Under water, there are a variety of eﬀects which are inﬂuencing the propagation of the sound waves. Our framework performs the real-time simulation of underwater signals for SONAR signal processing. The main focus lies in the implementation of an adaptive ray tracing method, which allows the simulation of time-varying multi-path propagation under the inﬂuence of a given sound velocity proﬁle and other environmental properties such as the structure of the sea bottom or the sea surface. Another feature of the simulation is the generation of spatially coherent noise signals with application to ambient sea noise in case of a multiple receiver system. Two special features of the simulation are the calculation of a time- and wind-dependent sea surface, as well as a possibility of using diﬀerent sediment types and user-deﬁned bottom surfaces. Another special feature of the simulation environment is the hardware simulation, which allows the use of hardwarespeciﬁc transmission functions like sensitivity curves of projectors and hydrophones.

The video shows the application of KiRAT for SONAR applications. Several send and receive hydrophones can be placed in an underwater environement with adjustment possibilities, such as sound velocity profiles (depth dependent). In addition, wind speed and direction can be adjusted (both is fed into a statical model for creating a time and location dependent water surface and corresponding noise). Furthermore, several moving target can be simulated. The channel simulation is based on a restricted 3D ray tracing scheme, that allows freqeuency dependant ray parameters (e.g. reflection and attenuation).

Corresponding Publications:

A. Namenas, T. Kaak, and G. Schmidt: Real-time Simulation of Underwarter Acoustic Channels, Proc. DAGA, Kiel, Germany, open access, 2017

We are delighted to announce that Marten Finck has been awarded the GaS prize for his Master's thesis on "Evaluation of Speech Quality Using Machine Learning".

In his work, he investigated possible side effects of magnetic resonance-guided focussed ultrasound treatment (MRgFUS) on speech quality in patients with neurological diseases such as Parkinson's disease and essential tremor. This innovative and non-invasive treatment method is used to reduce tremor, i.e. the shaking of limbs.

To evaluate the effects on speech, pre- and post-operative speech recordings of 56 patients were analysed: Speech quality was assessed in five categories (monotony, clarity, fluency, auditory effort and vocal tremor) through a survey with 21 participants and used to create a convolutional neural network (CNN). This generates an objective assessment of speech quality using mel frequency cepstral coefficients (MFCCs), fundamental frequency and loudness. A mean absolute error (MAE) of 0.81 on a scale of 0 to 10 was achieved, compared to a standard deviation of 0.67 for the survey participants compared to a reference assessment. The evaluation of the survey revealed minor positive and negative changes in speech quality, which were balanced overall and tended to indicate natural speech variations in connection with the patients' underlying illnesses.

Congratulations on this well-deserved honour!

Real-time Simulation of Underwater Channels

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