Course:Phys341 2020/Clarinet

Clarinet

The clarinet is a woodwind instrument. The clarinet is a very versatile instrument used in many genres, most notably classical and jazz. The clarinet itself consists of various parts including a single-reed mouth piece, a barrel, the upper and lower joint and the bell. A person who plays the clarinet is referred to as a clarinetist.

Fig.1 The construction of the clarinet

Structure

The B-flat clarinet is the most commonly used clarinet as it's most suitable for beginners. The second most common is the clarinet in A. The B-flat Clarinet is about 60cm long and and has a range of more than 3 octaves. There are various ways to make a clarinet; materials such as plastic, metal, ivory, and most notably different types of wood can all be utilized. Clarinets can be made from plastic, for beginners, but grenadilla wood is more suitable for intermediate players and professionals. Grenadilla wood has a higher relative density in comparison to boxwood, and as a result of that grenadilla wood allows for more air volume which makes for a more rich sound when played softly. While boxwood sufficed in the era of classical music, clarinetists today usually prefer grenadilla because of the dynamic range it provides. The mouthpiece of the clarinet is typically made up of hard rubber or plastic. As you can see from the photo on the right, the clarinet when played has one open end, so air can only be forced inside by one way. The one open end reflects back sound waves, and as a result it causes the reflections to reinforce each other- these sound waves created reinforce and reflect until they create a standing wave, the mouthpiece acting as a pressure antinode. This makes the clarinet similar to a pipe closed at one end and open at the other. Due to the clarinet being like a closed pipe, the distance between the highest pressure point and the point where the pressure is equal to the surrounding air must be one forth of the wavelength of the frequency of the note produced, however this can easily be modified by taking any pressure of the tone holes.

Single-reed

The clarinet uses a single-reed that is typically made by the cane of Arundo donax, a type of grass or synthetic materials. The ligature holds the reed in place on the mouthpiece and can be tightened and loosened to help produce the sound. The reed will rest on the players lower lip and the top of the mouthpiece will instead have the players teeth rested on it. How strongly you bite down or curl your lip in will change the players embouchure and is an appropriate way to change the tone and intonation. All single reeds are constructed in a similar manner, however, they vary in hardness, typically seen 1-5 or 1-10 depending on the manufacture. A beginner would start off using a hardness of 1 or similar, to more easily produce a sound in the lower register. As skill level progresses as well as knowledge of the upper register, the player will move up to a physically harder reed. Soft reeds move more than harder reeds, as a result of that soft reeds lower the frequency much more than hard reeds. Before producing a sound, the reed is usually placed in the players mouth to soften it. The reeds main purpose is to induce vibration, then the vibration of the reed at the innate frequency will cause the air surrounding it to be compress and expand many times per second, causing a sound wave. Blowing harder into the mouthpiece causes the air pressure to increase and decrease on a larger scale which then increases sound level. When the pressure in the mouth piece rises, the reed is forced outwards. The reed will increase or decrease the the volume with high and low pressure. The reed vibrates at one frequency, but when played at high volumes, the reed will generate harmonics. The reed controls the air flow, and in most cases it's a good thing the reed can oscillate like a spring by itself, however, the reed can also cause squeaking. The reed converts steady power into acoustic power.

Registers

The clarinet is able to play in three registers. The Chalumeau register: low E to third line Bb, Clarion register: third line B to thumb C, and the Altissimo register which consists of everything above thumb C. The chalumeau register has a rich, full sound. The clarion register has a brighter tone. The Altissimo register has the brightest tone, which at times can be shrill. The notes in the clarion register tend to bend easier than the notes in the chalumeau register, this is because the notes in this range have only two bore resonances that coincide with harmonics. Once the register key is used, the systematic differences between odd and even numbers almost disappear and the timbre becomes brighter and more clear.

The clarinet's register key is utilized to achieve the second register. The key when pressed will open an additional hole on the side of the instrument, thereby raising the clarinet's pitch by a twelfth (19 semitones). The upper register can be played by forcing the air column to vibrate at it's third harmonic frequency instead of the fundamental. The open hole will produce a pressure node at the point where the fundamental mode produces a pressure variation, so that the lowest vibrational mode cannot be sustained.

Harmonics

The clarinets harmonic series acts as a closed pipe. The reed end of the clarinet acts as a node, and the first open hole acts as the antinode. As a result of this, it should only produce odd harmonics. The reed vibration has both odd and even harmonics but in the lower register only the odd harmonics set up. As a result, the sound spectrum has strong first and third harmonics but weak second and fourth harmonics. In figure one, it is shown that there are some even harmonics, however they are very weak in the lower registers. The higher notes of the clarinet, as shown in figure two, display much less upper harmonics than the lower notes, leading us to believe that the upper register of the clarinet does not behave like a closed pipe to the extent of the lower registers do. The sound of the clarinet resembles a sine wave when played softly, but that resemblance dissipates as you explore the higher registers.

Fig 2. Clarinet middle C. Own work.

Fig 2. Upper register note f6. Own work.