BRASSISSIMA · SECTION 2

Acoustic foundations

Simple tubes are the starting point: waves, reflections and resonances can be investigated systematically. The historical experiments are being extended with current simulations and illustrative animations.

From experiments to a new stage of the project: years of experimental work are being reviewed and presented anew from 2026. Videos illustrate processes in space and time; PDFs provide room for derivations, measurement details and extended analyses.

Sound propagation in a tube: reflection and radiation

Left closed · Right open. Top to bottom: positive pulse →; negative reflection ← plus a small radiated part →.

Closed on the left, open on the right. A positive pressure pulse travels from the closed to the open end. At the open end, most is reflected as a negative pulse; a small part radiates outwards. Schematic for strong reflection at low frequencies: no fixed energy or amplitude ratio is implied.

Current videos

The series builds progressively: please start with Video 1. This section contains the following episodes.

For clear diagrams and labels, please select 1080p (Full HD) in the YouTube video quality settings whenever available.

VIDEO 1

1. Waves, impedance and reflections

How waves propagate in a tube closed at one end, reflect and form resonances.

English narration · German subtitlesWatch on YouTube ↗

VIDEO 2

2. Local perturbations of a cylinder

A local expansion or constriction: how does its position influence frequency and magnitude?

English narration · German subtitlesWatch on YouTube ↗

Watch the complete video series →

Current PDF documentation · from 2026

No new PDF edition from 2026 onward is linked in this section yet. New publications will be added with their language, version and date; earlier editions can be found in the legacy archive.

Legacy archive · earlier documentation

Historical experiments, simulations and analyses, previously collected in Revision 20. These documents remain available for context and traceability. They are distinct from publications issued from 2026 onward.

Identifiers: L1–L3 = original level · G = German · E = English. Document numbers and original addresses are retained.

Collected foundations in physics and mathematics relevant to the projectGerman · PDF · Level L1 · Legacy · Revision 202-L1-G-Sideletter-1-Basics-Physik
Comparing the acoustics of simple geometries: cylinder, cone and frustumGerman · PDF · Level L1 · Legacy · Revision 202-L1-G-Teil-2B-Pert-Cyl-Cone-Frustum
Acoustic properties of cylindrical tubes: the transfer matrix methodGerman · PDF · Level L2 · Legacy · Revision 202-L2-G-Sideletter-2
Acoustic changes caused by perturbations of cylindrical tubes, based on A.R.T.German · PDF · Level L2 · Legacy · Revision 202-L2-G-Sideletter-3-ART
Perturbations of closed–open geometries: cylinder and frustumGerman · PDF · Level L2 · Legacy · Revision 202-L2-G-Teil-2C-Pert-Virt-Cyl-Frustum
Acoustics of perturbated cylindrical tubes (advanced), based on OpenwindEnglish · PDF · Level L2 · Legacy · Revision 202-L2-E-Sideletter-4-Openwind
Where are the limits? Extreme perturbations of closed-open cylindrical tubesEnglish · PDF · Level L3 · Legacy · Revision 202-L3-E-Sideletter-6-OW-limits
Discrepancies of perturbated tubes, Openwind vs. experimental measurementsEnglish · PDF · Level L3 · Legacy · Revision 202-L3-E-Sideletter-5-Measured-vs-OW
Summary of experiments with a closed open cyl. tubeEnglish · PDF · Level L2 · Legacy · Revision 202-L2-E-Openwind-Summary of experiment on a cylindrical tube

Historical note: another work, “Inria / Openwind – Perturbation of cylindrical tubes – simulation vs. measurements”, was listed as unpublished. There is still no download link for it. The earlier experiments include both A.R.T. and OpenWind simulations; the method used is stated in the respective document.