Sound EnergyTo truly understand the sound production of the trumpet, simple concepts of sound should be introduced.
Sound energy is unique and particular with its specifications. Sound must be created at a source which is typically a vibration; known as a cycle of motion. A source can be just about anything, but in this case we will be dealing with the musicians lips. This cycle of motion creates a mechanical wave also known as a transfer of energy through a material due to vibration. A material can be a made out of a solid, liquid or gas, and because trumpets are not usually played into water or onto a wall, the sound will be transferred through air (also known as a gas). The Wave of SoundWaves of sound are sometimes modelled through wave patterns similar to a sinusoidal function. This is called a transverse wave. Transverse waves have many different components to them but are quite simple to read.
But sounds wave from a trumpet do not appear as a transverse wave, the appear as a longitudinal wave which is a wave where particles vibrate parallel to the direction of the flow of energy. This flow of energy and direction will be out the bell of the trumpet.
DefinitionsAmplitude: The maximum displacement of a wave from its equilibrium point.
Wavelength: The distance between two similar point in successive identical cycles in a wave, such as a from crest to crest to trough to trough. Rarefaction: Region of the longitudinal wave when the mediums particles are farther apart. Compression: Region of the longitudinal wave when the mediums particles are bunched together. |
The Closed Air-Column |
One the left are closed air columns, on the right are open air columns.
The three valves on a trumpet
A staff representing a perfect eighth (one octave)
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There are two main types of air columns, the closed air column and the open air column. The open air column is when sound is travelling through an object in which it has two open ends. An instrumental example of this would be the flute. But because the trumpet only allows one exit for air to escape, we are focusing on the closed air column. Since we are dealing with longitudinal waves the nodes (places in which both waves meet the rest axis) are considered the areas of compression. Which mean the antinodes (places in which the wave is at its maximum point) are considered rarefaction. Harmonic frequencies are the fundamental sounds of a trumpet, or the sounds produced when there is no alteration to sound whatsoever. Each harmonic will be placed on odd numbers only, the even-numbered harmonics do not exist in closed air columns. As you can see these are the valves to a trumpet. When non of the valves are being held down the note C or G can be played. not only the 2 but different frequencies of the two. If a note has more frequency the higher the note will be. If C is the first harmonic (Fundamental), the third harmonic (First Overtone) will be the first variation of the note at a higher frequency. These two notes are a octave apart These two note on the staff both represent C. If the lower note has a frequency of 262 Hz, then the next will be 524 Hz. This is modelled by this equation when, f = Frequency n= Overtone fn = f x n |
When the closed air column is expanded but keeps a consistent frequency the sound production can be changed. This is called resonance. Look at the variables for resonance and different sounds in the next tab.