Wind instrument

For example, saxophones are typically made of brass, but are woodwind instruments because they produce sound with a vibrating reed.

Under suitable conditions, the valve will reflect the pulse back, with increased energy, until a standing wave forms in the tube.

For recorders and flue organ pipes this slit is manufactured by the instrument maker and has a fixed geometry.

This perturbation is strongly amplified by the intrinsic instability of the jet as the fluid travels towards the labium.

The amplification of perturbations of a jet by its intrinsic instability can be observed when looking at a plume of cigarette smoke.

The same jet oscillation can be triggered by gentle air flow in the room, which can be verified by waving with the other hand.

One can demonstrate that this reaction force is the source of sound that drives the acoustic oscillation of the pipe.

A quantitative demonstration of the nature of this type of sound source has been provided by Alan Powell[9] when studying a planar jet interacting with a sharp edge in the absence of pipe (so called edgetone).

The sound radiated from the edgetone can be predicted from a measurement of the unsteady force induced by the jet flow on the sharp edge (labium).

In all these cases (flute, edgetone, aeolian tone...) the sound production does not involve a vibration of the wall.

[10] The sound production in a flute can be described by a lumped element model in which the pipe acts as an acoustic swing (mass-spring system, resonator) that preferentially oscillates at a natural frequency determined by the length of the tube.

One 2011 study focused on brass and woodwind instruments observed "temporary and sometimes dramatic elevations and fluctuations in IOP".

[12] Another study found that the magnitude of increase in intraocular pressure correlates with the intraoral resistance associated with the instrument and linked intermittent elevation of intraocular pressure from playing high-resistance wind instruments to incidence of visual field loss.