Flue pipe

Flue Pipe

A flue pipe is a type of organ pipe that produces sound by directing a stream of air against a sharp edge, causing the air within the pipe to vibrate. Flue pipes are a fundamental component of pipe organs, which are used in a variety of musical and liturgical settings.

A set of flue pipes in a pipe organ.

Construction

Flue pipes are typically made from either metal or wood. The choice of material affects the tonal quality of the sound produced. Metal pipes are often made from alloys such as tin and lead, while wooden pipes are usually constructed from hardwoods like oak or maple.

The basic structure of a flue pipe consists of several key components:

• Foot: The lower part of the pipe, which is inserted into the windchest and receives the air supply.
• Mouth: The opening where the air stream exits the foot and strikes the labium, creating sound.
• Labium: The sharp edge against which the air stream is directed, causing the air column within the pipe to vibrate.
• Body: The main resonating chamber of the pipe, which determines the pitch and timbre of the sound.

Function

The sound production in a flue pipe is based on the principle of aerodynamics. When air is forced through the foot of the pipe, it exits through the mouth and strikes the labium. This interaction causes the air column inside the body of the pipe to vibrate at a specific frequency, producing sound.

The pitch of the sound is primarily determined by the length of the pipe. Longer pipes produce lower pitches, while shorter pipes produce higher pitches. The diameter and shape of the pipe also influence the timbre and volume of the sound.

Types of Flue Pipes

Flue pipes can be classified into several types based on their construction and sound characteristics:

• Open Flue Pipes: These pipes are open at both ends and produce a bright, clear sound. They are commonly used for principal and flute stops in organs.

• Stopped Flue Pipes: These pipes have a stopper at one end, which lowers the pitch by an octave compared to an open pipe of the same length. They produce a softer, more mellow sound.

• Harmonic Flue Pipes: These pipes are designed to produce overtones, enhancing the richness and complexity of the sound.

A view of flue pipes in a church organ.

Acoustic Properties

The acoustic properties of flue pipes are influenced by several factors, including the shape and size of the pipe, the material used, and the air pressure supplied. The interaction between these elements determines the harmonic content and overall sound quality.

The harmonics produced by a flue pipe contribute to its unique sound. The presence of certain harmonics can make the sound brighter or darker, depending on the design of the pipe.

Maintenance and Tuning

Regular maintenance and tuning are essential for the optimal performance of flue pipes. Tuning involves adjusting the length of the pipe or the position of the stopper to achieve the desired pitch. Maintenance may include cleaning the pipes and ensuring that the air supply is consistent and free of obstructions.

Related Pages

• Pipe organ
• Organ stop
• Aerophone