Civic technology platforms are increasingly developed through collaborative processes involving diverse stakeholders. Yet existing participatory design literature offers limited theoretical attention to collaborative trajectories that deviate from a canonical model in which co-design is structured and intentional from the outset. This paper presents a reflective account of the development of “dédédé”, an online platform that invites citizens to informally document and share observations about their neighborhoods. The platform was initially conceived and developed by a team of technologists, then evolved through two co-design phases involving progressively broader stakeholder communities: first with urban designers and other practitioners experienced in facilitating machiaruki (“town-walking”) workshops, then with city officials and real estate developers interested in leveraging the platform for machizukuri (“town-building”) efforts. We show that these phases produced qualitatively distinct collaborative dynamics: the first characterized by receptive redesign, in which domain expertise corrected the implicit assumptions of the technical team; the second by active negotiation and resistance, in which the design knowledge accumulated in the first phase became a resource (design anchor) for mediating competing stakeholder visions. We argue that such staged co-design processes represent a recognizable and undertheorized mode of civic technology development, with distinct benefits and risks.

We propose a sinusoidal synthesis method based on instantaneous frequency (IF) attractors, which correspond to harmonic frequency trajectories. The algorithm is novel in extracting accurate sinusoidal components. Since the continuity of IF attractors is well-defined and simple to detect, the IF attractors can be extracted from audio signals without any explicit constraint or complicated algorithm; therefore, they can be directly applied to sinusoidal synthesis. Accuracy of IF attractor analysis can be further improved by time-warping analysis, which improves resolution for harmonic components whose frequencies that change rapidly. We describe the procedure for sinusoidal synthesis and precise phase estimation along with examples and also evaluate the effect of time-warping on analysis and synthesis of speech

We propose a sinusoidal synthesis method based on the instantaneous frequency (IF) attractors which well correspond to harmonic frequency trajectories. We demonstrate that IF attractors can be directly applied to sinusoidal synthesis. Since the continuity of IF attractors is well-defined and simple to detect, extraction of IF attractors can be done without any explicit constraint and needs no complicated algorithm such as peak-tracking of short-time spectra. We also describe the procedure for sinusoidal synthesis and precise phase estimation along with examples.

This paper proposes a technique for estimating the harmonic frequencies based on instantaneous frequency (IF) of a speech signal. The main problem is how to decompose the speech signal into the harmonic components. For this purpose, we use a set of bandpass-filters, each of whose center frequencies changes with time in such a way that it tracks the instantaneous frequency of its output. As a result, the outputs of the band-pass filters become the harmonic components, and the instantaneous frequencies of the harmonics are accurately estimated. To evaluate the effectiveness of the approach, we apply it to pitch extraction. The pitch extraction is simply accomplished by selecting the correct fundamental frequency out of the harmonic frequencies. The most significant feature of the pitch extractor is that the extracted pitch contour is smooth and it requires no post-processing such as nonlinear filtering or any smoothing processes.