FlueBricks: A Construction Kit of Flute-like Instruments for Acoustic Reasoning

Abstract

We present FlueBricks, a construction kit for acoustic reasoning via building and customizing flute-like instruments. By assembling generator, resonator, and connector modules that embody various aeroacoustic properties, users gain deeper understanding of how blowhole, tube length, and tone-hole placement alter onset, pitch, and timbre through hands-on experimentation. This forms a designer-player loop of configuring and playing to form, test, and refine acoustic behaviors-acoustic reasoning-shifting acoustic instruments from static artifacts to dynamic systems. To understand how users engage with this system, we conducted an exploratory study with 12 participants ranging from novices to professional musicians. During their explorations, we observed participants fluently switching between designer and player roles, scaffolding designs from familiar instruments, forming and refining their acoustic understanding of length, tone holes, and generator geometry, reinterpreting modules beyond their intended functions, and using their creations for performative acts such as pedagogical showing and musical expression. These collectively demonstrated FlueBricks's potential as a pedagogical tool for embodied acoustic reasoning.

Figures (16)

• Figure 1: Overview of the FlueBricks modular component system. A complete flute constructed from FlueBricks modules, comprising three component families---Generator, Resonator, and Connector---each exposing parameter-level control for acoustic reasoning. The system offers two tiers: a standard set of pre-assembled variants for getting started, and an advanced set for fine-grained acoustic manipulation. A zoomed-in sketch illustrates the Generator's internal structure, highlighting its modularity and granularity.
• Figure 2: Three coupled phases of flute-like sound production. (a) Air-jet formation: blowing into the mouthpiece creates a focused jet of air. (b) Jet-edge interaction: the air jet encounters the labium, a sharp edge, and oscillates between the inside and outside of the pipe, producing an edge tone. (c) Resonance amplification: The jet-labium interaction generates pressure oscillations that excite the resonator, which selectively reinforces certain frequencies through resonance to sustain the sound. These acoustic mechanisms inform FlueBricks's generator design: following the granularity principle, we decompose the generator into 8 acoustically meaningful submodules that map to these geometries (flue tunnel, air chamber, windway, window, splitting edge, sound chamber), enabling parameter-level control over tone production.
• Figure 3: How changes in pipe geometry affect pitch. This figure compares three types of resonator configurations. Left: an open pipe creates sound by supporting vibrations along its full length, with both ends open. Middle: a closed pipe supports a different vibration pattern, resulting in a longer effective length and a lower pitch compared to an open pipe of the same size. Right: a tone hole acts like a shortcut: if large enough, it defines a new endpoint for vibration, effectively shortening the pipe and raising the pitch. The cyan region shows the effective length---the part of the pipe that actually shapes the sound.
• Figure 4: Generator fine-grained control configuration. FlueBricks enables airflow and tone production control through parameter-level manipulation. (a--f) The generator is assembled from eight modular parts, each controlling specific acoustic parameters. (b) Varying air deflector angles (90°, 78°, 35°) reshapes airflow, shifting tone from focused high frequencies to overtone-rich textures. (c) Changing the air facade (sharp, flat, arc) affects timbre brightness and ease of onset. (e--f) A shorter splitting edge raises the overblowing threshold, improving pitch stability in lower registers.
• Figure 5: Resonator length control configuration. FlueBricks enables pitch control through modular length manipulation. (a) Basic nodes of different lengths provide discrete pitch steps. (b-1 to b-4) Stacking nodes extends the air column, progressively lowering pitch and deepening timbre. (c) Attaching an adapt cap shifts to closed-pipe mode for further pitch lowering. (d) Telescoping nodes enable continuous pitch bending for glissando effects.