Juha Backman

Analysis, modeling, and real-time sound synthesis of the kantele, a traditional Finnish string instrument

The kantele is a unique old Finnish string instrument that has been found to have interesting acoustical principles of sound production, including nonlinear behavior and dual-mode vibrations of the strings. The main interest was in the most traditional five-string kantele. It is a musical instrument tuned to the pentatonic scale. The authors describe results from a study where the acoustics of the instrument were first analyzed, its sound generation principles were then modeled computationally, and finally a real-time sound synthesis algorithm was developed for a floating-point signal processor. The simplified model of the kantele, when properly adjusted, leads to synthetic sounds that well resemble the original instrument.<<ETX>>

Modelling of human directional and spatial hearing using neural networks

The task of modeling and simulating human directional and spatial hearing has been difficult because of the complexity of the auditory system. The authors approach the problem from the perspective of artificial neural networks that reveal new possibilities for developing advanced models of directional and spatial hearing that are able to learn desired forms of behavior. They discuss the general framework of the topic, possible approaches and model implementations, and interesting applications of such models. Experimental results show that a combination of a dummy head, an auditory preprocessor, and a neural network may learn directional discrimination that in simple cases outperforms human listeners, showing also some ability of generalization.<<ETX>>

Audio and ultrasonic transducers based on electrothermomechanical film (ETMF)

A transducer material consisting of foamized plastic, called electrothermomechanical film (ETMF), is introduced. The film has conductive electrodes on at least one side, so it can be used with either an electrostatic or electrodynamic driving force. The film can be used both as a transmitter and a receiver at audio and ultrasonic frequencies, also in hydroacoustical applications. Lumped-component and one-dimensional distributed-parameter models are developed to examine the behavior of the film. Frequency responses and sensitivities predicted by the models are compared with measured data. Audio applications of the film as a loudspeaker (tweeter and full-range) are introduced with data collected from prototypes. Means of controlling radiation pattern and frequency response are briefly discussed. Applications of the film as a microphone, hydrophone, and hydroacoustic source for audio and ultrasonic frequencies are mentioned.<<ETX>>

Digital Realisation Of Phono (RIAA) Equalisers

The author presents a digital realization of phono equalizers, using a simple first-order analog pre-emphasis filter combined with a digital IIR (infinite impulse response) type filter. This approach makes it possible to use a relatively simple digital filter to achieve an accurate frequency response and a good dynamic range. Computations show that a relatively simple second-order digital filter in combination with a first-order analog filter yields a response accuracy practically unobtainable with conventional phono equalizers, especially when the influence of component tolerances, temperature, etc. is taken into account. Achieving good noise and distortion properties in the digital equalizer is easy, and the analog stage is much simpler than in conventional completely analog equalizers. >