Browsing by Author "Välimäki, Vesa, Prof."

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    Analysis, perception, and synthesis of the piano sound
    (Aalto-yliopiston teknillinen korkeakoulu, 2010) Lehtonen, Heidi-Maria; Välimäki, Vesa, Prof.; Signaalinkäsittelyn ja akustiikan laitos; Department of Signal Processing and Acoustics; Aalto-yliopiston teknillinen korkeakoulu; Välimäki, Vesa, Prof.
    This thesis deals with the signal analysis, auditory perception, and physics-based synthesis of the piano sound. Contributions of this thesis can be grouped into four main categories: Analysis and modeling of the sustain pedal effect, analysis of harmonic and inharmonic musical tones by means of an inverse comb filter, loss filter design for waveguide piano synthesis, and perception of longitudinal vibrations in piano tones. The sustain pedal effect is studied through signal analysis of recorded tones, and the results show that the use of the sustain pedal increases the decay times of middle range tones, increases beating, and makes the sounds more reverberant. Based on the results, an algorithm is designed for simulating the sustain pedal effect. Objective and subjective studies show that the algorithm is capable of producing the main effects of the sustain pedal. The signal analysis of tones played with a partial sustain pedal reveals that the tone decay can be divided into three distinct time intervals, namely the initial decay, the damper-string interaction, and the final free vibration. Additionally, the nonlinear amplitude limitation during the damper-string interaction can excite missing modes in the lowest piano tones. Decomposition of harmonic and inharmonic musical instrument tones to tonal and noise components and selecting single partials with an inverse comb filter structure is discussed. The filters are designed based on the fundamental frequency and the inharmonicity coefficient, and they are found to provide a simple and efficient analysis tool for musical signals. A multi-stage ripple filter structure for modeling the complicated decay process of the piano tones is presented. The filter is capable of accurately matching a desired number of partial decay times or, alternatively, modeling the overall decay characteristics of a piano tone. Finally, the threshold of audibility is sought for perception of longitudinal components in fortissimo piano tones through formal listening tests. The results suggest that the longitudinal components are audible up to note C5 (fundamental frequency 523 Hz), but based on the listeners' opinions modeling the longitudinal components in a piano synthesizer up to note A3 (fundamental frequency 220 Hz) only is sufficient.
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    Sonic gestures and rhythmic interaction between the human and the computer
    (Aalto University, 2012) Jylhä, Antti; Erkut, Cumhur, Dr.; Signaalinkäsittelyn ja akustiikan laitos; Department of Signal Processing and Acoustics; Sähkötekniikan korkeakoulu; School of Electrical Engineering; Välimäki, Vesa, Prof.
    This thesis addresses the use of sonic gestures as input in human-computer interaction with a special applicability focus on rhythmic interactive systems and their design and evaluation. Sonic gestures are defined as human-generated sounding actions which convey information to a computational system. Examples of such gestures are impulsive sounding actions such as hand claps and finger snaps, sustained actions such as humming and blowing, and iterative actions, such as tapping a table to the beat of music. The use of sonic gestures at the interface requires analysis algorithms that are capable of tracking the desired information from an audio stream containing the human-generated sounds. In interactive systems, these algorithms must be capable of real-time processing. In this thesis, the focus is on percussive sonic gestures, which can be seen to be analogous to the sounds of percussive instruments. Therefore, it is reasonable to assume that the same tools that are applied for retrieving information from drums and percussion in music can be deployed for sonic gesture analysis. This work presents algorithms for the classification of different percussive sounds, such as different types of hand claps. To demonstrate the use of sonic gestures, a hand clap interface capable of recognizing different hand clap types and extracting continuous information, such as the tempo, from a clapping sequence has been developed. This interface has been utilized in the development of various rhythmic prototype applications, most importantly a system called iPalmas, an interactive Flamenco rhythm tutor. The iPalmas system can produce realistic-sounding synthetic Flamenco hand clapping patterns to the user, listen to the clapping of the user, and give audiovisual feedback on the learning and performance. The iPalmas system was evaluated in a subjective experiment, resulting in qualitative and quantitative findings related to the system design, the human capabilities, and the interaction. In conjunction with this evaluation, a structured framework for evaluating this kind of systems has been proposed. Based on the evaluation results, the system has undergone iterative development of the audiovisual feedback elements. The main outcomes of the thesis are a novel definition of sonic gestures in human-computer interaction and a taxonomy of the information they can convey to computational systems and the interactive iPalmas system, resulting in several relevant findings that can be generalized in the design and evaluation of rhythmic interactive systems.