page_title: Clarinet
section_title: Acoustics
hierarchical_section_title: Clarinet / Characteristics / Acoustics
caption_attribution_description: Deutsch: Vierteltondoppelklarinette von Fritz Schüller Markneukirchen.
context_page_description: The clarinet is a family of woodwind instruments. It has a single-reed mouthpiece, a straight, cylindrical tube with an almost cylindrical bore, and a flared bell. A person who plays a clarinet is called a clarinetist.
  While the similarity in sound between the earliest clarinets and the trumpet may hold a clue to its name, other factors may have been involved. During the Late Baroque era, composers such as Bach and Handel were making new demands on the skills of their trumpeters, who were often required to play difficult melodic passages in the high, or as it came to be called, clarion register. Since the trumpets of this time had no valves or pistons, melodic passages would often require the use of the highest part of the trumpet's range, where the harmonics were close enough together to produce scales of adjacent notes as opposed to the gapped scales or arpeggios of the lower register. The trumpet parts that required this specialty were known by the term clarino and this in turn came to apply to the musicians themselves.
context_section_description: Sound is a wave that propagates through the air as a result of a local variation in air pressure. The production of sound by a clarinet follows these steps:
  The mouthpiece and reed are surrounded by the player's lips, which put light, even pressure on the reed and form an airtight seal. Air is blown past the reed and down the instrument. In the same way a flag flaps in the breeze, the air rushing past the reed causes it to vibrate. As air pressure from the mouth increases, the amount the reed vibrates increases until the reed hits the mouthpiece.
  At this point, the reed stays pressed against the mouthpiece until either the springiness of the reed forces it to open or a returning pressure wave 'bumps' into the reed and opens it. Each time the reed opens, a puff of air goes through the gap, after which the reed swings shut again. When played loudly, the reed can spend up to 50% of the time shut. The 'puff of air' or compression wave (around 3% greater pressure than the surrounding air) travels down the cylindrical tube and escapes at the point where the tube opens out. This is either at the closest open hole or at the end of the tube (see diagram: image 1).
  More than a 'neutral' amount of air escapes from the instrument, which creates a slight vacuum or rarefaction in the clarinet tube. This rarefaction wave travels back up the tube (image 2).
  The rarefaction is reflected off the sloping end wall of the clarinet mouthpiece. The opening between the reed and the mouthpiece makes very little difference to the reflection of the rarefaction wave. This is because the opening is very small compared to the size of the tube, so almost the entire wave is reflected back down the tube even if the reed is completely open at the time the wave hits (image 3).
  When the rarefaction wave reaches the other (open) end of the tube, air rushes in to fill the slight vacuum. A little more than a 'neutral' amount of air enters the tube and causes a compression wave to travel back up the tube (image 4). Once the compression wave reaches the mouthpiece end of the 'tube', it is reflected again back down the pipe. However at this point, either because the compression wave 'bumped' the reed or because of the natural vibration cycle of the reed, the gap opens and another 'puff' of air is sent down the pipe.
  The original compression wave, now greatly reinforced by the second 'puff' of air, sets off on another two trips down the pipe (travelling 4 pipe lengths in total) before the cycle is repeated again.
  The cycle repeats at a frequency relative to how long it takes a wave to travel to the first open hole and back twice (i.e. four times the length of the pipe). For example: when all the holes bar the very top one are open (i.e. the trill 'B' key is pressed), the note A4 (440 Hz) is produced. This represents a repeat of the cycle 440 times per second.
  In addition to this primary compression wave, other waves, known as harmonics, are created. Harmonics are caused by factors including the imperfect wobbling and shaking of the reed, the reed sealing the mouthpiece opening for part of the wave cycle (which creates a flattened section of the sound wave), and imperfections (bumps and holes) in the bore. A wide variety of compression waves are created, but only some (primarily the odd harmonics) are reinforced. These extra waves are what gives the clarinet its characteristic tone.
  The bore is cylindrical for most of the tube with an inner bore diameter between 14 and 15.5 millimetres (0.55 and 0.61 in), but there is a subtle hourglass shape, with the thinnest part below the junction between the upper and lower joint. The reduction is 1 to 3 millimetres (0.039 to 0.118 in) depending on the maker. This hourglass shape, although invisible to the naked eye, helps to correct the pitch/scale discrepancy between the chalumeau and clarion registers (perfect twelfth). The diameter of the bore affects characteristics such as available harmonics, timbre, and pitch stability (how far the player can bend a note in the manner required in jazz and other music). The bell at the
caption: Schüller's quarter-tone clarinet
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