Acoustic and Perceived Effects of the Flute’s Stopper Mechanism

Although many of the effects of the flute’s design and mechanisms have been previously studied, the flute’s stopper remains relatively unexplored. Stoppers are traditionally made of cork, are used to seal the upper end of the headjoint tubing, and determine the overall intonation of the flute. However, new stoppers made of different types of materials have been created to serve an additional purpose: to improve various aspects of player performance. These new non-cork stoppers vary in design and material, and claim to improve players’ projection, resonance, response, and other qualities.

This research project discusses the history of the flute’s stopper and its functions, usage, and effects to improve general stopper knowledge and assist flutists interested in trying or purchasing non-cork stoppers available today. Because only three small studies have been published on the stopper’s acoustic and perceived effects to date, two single-blind experiments were conducted to determine the stoppers’ potential acoustic and perceived effects on listener and player perception. Five of the most popular stoppers available today were tested: the Bigio Stopper, Celestine Rexonator, Seidman Flute Stopper Plug, Swap-Stopper, and the traditional cork stopper.

To determine the stopper’s acoustic effects, which can be quantified, an acoustic experiment was conducted to investigate the stoppers’ effect on intensity in decibels (which correlates with perceived loudness) and spectral centroid in hertz (which correlates with perceived tonal brightness). Perception tests were conducted to examine how both players and listeners perceive the stoppers’ effects on projection, response, tone quality, and timbre. The results of these experiments will help flutists better understand the effects of the stopper and navigate the stopper-makers’ claims about non-cork stoppers available for purchase today.