The present invention generally relates to stringed musical instruments and more particularly to a stringed instrument, such as an acoustic guitar, comprising a sound chamber, or body, in which sound waves generated by the plucked strings are amplified by the vibrations of the materials forming the sound chamber and emitted from the sound chamber. For musical instruments, such as flat-topped acoustic guitars, the sound chamber has a front (also referred to as the soundboard), back, and sides. For some of these instruments, the strings are attached on one end to a head at the end of a neck extending from the sound chamber, and attached at the other end to a bridge which is attached to the soundboard. The flat-topped acoustic guitar is so identified because its soundboard is generally flat, as opposed to an arched top guitar which, as suggested by the name, has an arching top with three dimensional characteristics. The term flat-topped acoustic guitar includes both steel string acoustic guitars as well as nylon string classical guitars.
Under the traditional design of a flat-topped guitar, the soundboard has a single opening for the emission of sound waves, which opening is disposed beneath the strings of the instrument, the opening being located centrally with respect to each side of the instrument.
When the strings vibrate, the vibrations travel through the bridge to the soundboard, such that the entire soundboard vibrates. The rest of the sound chamber amplifies the vibrations of the soundboard, with the sound waves primarily emitted from the soundhole.
In the case of acoustic guitars, the sound chamber generally comprises a top, known as the soundboard, a back, and sides. The lower bout is the large rounded bottom of a traditional guitar and the upper bout is the smaller, rounded and convex shape at the top. Under traditional design, the shape of the sound chamber of acoustic guitars is in the shape of a number “8”, with the upper half, i.e., the upper bout, being smaller than the bottom half, i.e., the lower bout. The upper bout and lower bout are separated by the “waist” of the guitar, which is the concave transition between the upper and lower bouts. For traditional designs, the sound hole is located almost entirely in the upper bout of the instrument.
For the typical right handed guitar player, the upper bout of the guitar is adjacent to the player's left arm, and the lower bout is adjacent to the player's right arm. The left hand is utilized for fingering notes on a fingerboard (also referred to as the “fretboard”), where the fingerboard is disposed on the neck. The right hand is utilized for picking or strumming the strings. For the remainder of this description, it will be assumed that the guitar is a “right handed” guitar, i.e., built to be played by a right-handed person. However, correlating the description for a left-handed guitar only requires the assumption that the right hand is utilized for fingering the notes and the left hand is utilized for picking or strumming the strings.
The sides of the guitar may, for purposes of description, be identified with respect to the strings. The treble strings of the instrument are on the side of the instrument facing downward as it is played in the conventional manner, while the bass strings are on the side of the instrument generally facing upward as the instrument is played. Using the strings as a point of reference, the sides of a guitar may be referred to as the treble side and the bass side. With respect to the string orientation described above, the side of the guitar facing downward while being played is considered the treble side of the instrument and the side of the guitar facing upward is considered as the bass side of the instrument. The upper bout therefore may be further described as having a treble side upper bout and a bass side upper bout. Likewise, the lower bout may be further described as having a bass side lower bout and a treble side lower bout. The bass and treble sides of the lower bout meet at the bottom center of the guitar, where the meeting sides of the lower bout are glued to an an internal structure known as the “tailblock.”
Under the traditional design for guitars, the exterior of the sound chamber is symmetric, where the treble side and bass side are mirror images of one another. However, over the years, instrument makers have modified the traditional design. One of the most common of these modifications, which results in an asymmetrical sound chamber, has been to fashion a “cut-away” into the treble side of the upper bout and upper portion of the soundboard adjacent to the neck on the treble side to allow the player greater access to the portions of the fingerboard adjacent to the body of the guitar. Other modifications have also been made, such as placing the sound hole in a different position than directly under the strings. As another modification, some instrument makers have placed bevels in various portions of the instrument, such as where the soundboard of the instrument joins the sides. Under the traditional design, the soundboard and sides of the instrument are at a right angle to each other, defining a common edge. This common edge may have a binding material, such a wood, plastic, or other trim, which protects the soundboard and side from impact damage. Some instrument makers “soften” this common edge by forming a rounded transition section from the side to the soundboard, forming a beveled edge (i.e. a bevel) for a portion of the common edge.
The inventor herein has invented a structural feature referred to as the “Ryan bevel” which has since been utilized and/or modified by others practicing the guitar making art. The Ryan bevel generally comprises an approximate 45 degree chamfer on the bass side lower bout. The Ryan bevel feathers in just above the bass-side waist and feathers out just beyond the centerline of the guitar at the tailblock area. The Ryan bevel has some acoustic advantages but it also creates greater comfort for the player since the player's right arm is resting on a chamfered, wide surface rather than against the relatively sharp corner of the guitar where the sides and soundboard of a conventional acoustic guitar meet.
Another modification made in recent years to acoustic flat-topped guitars has been the placing of an opening or cutout in the bass side upper bout of the guitar, where this opening is referred to as a “soundport”. The soundport, as with the soundhole beneath the strings in the soundboard, provides an emission means for the sound waves generated by the strings as amplified by the sound chamber. For soundports located in the usual position on the bass side upper bout, sound waves emitted from the soundport are directed toward the face of the guitar player.
The known soundports present several problems and disadvantages. First, placing a soundport in the side of the instrument can result in diminished structural strength. For example, the sides of a guitar typically have a wall thickness ranging from 0.060″ to 0.090″, with about 0.075″ being the most common thickness. Given this relatively thin wall, and the continuous load imposed on a guitar body by the string tension—approximately 180 pounds for a steel string guitar—the structural integrity of the load-bearing components of the instrument is always a concern. However, when a side has one or more cutouts for the soundports, the structural integrity may be adversely impacted.
One method of resolving this problem is to place a reinforcement member or other structure within the interior of the sound chamber, such as thicker backing on the interior side of the bout in which the soundport will be placed. However, this method has its own disadvantages. Utilizing a reinforcement member in this manner has the disadvantage of adding to the weight of the instrument and/or adversely impacting the acoustic properties of the sound chamber. Adding structural reinforcement on the inside of the instrument utilizes additional materials and is time consuming, thereby resulting in greater manufacturing expense. A reinforcement member can also create additional stresses on the side of the instrument, because the additional piece of wood glued to the side will not always shrink and expand at the same rate as the side material, which can create stresses and possible cracks in the side during relative humidity fluctuations.
Another problem presented by the known soundports is that when the soundports are located in the upper bout of the instrument, they are located in a portion of the instrument which is not as acoustically active as other portions of the sound chamber, such as in the lower bout behind and/or adjacent to the bridge.
The orientation of the known soundports is typically directed upward into the face of the player, with the axis of the soundport generally perpendicular to the front or soundboard of the instrument. It is to be appreciated that because an audience is typically located at the front of the instrument, the axis of a soundport located in the upper bout of the instrument will be perpendicular to the general direction of the audience. Moreover, depending upon the position in which the player holds the instrument, this location is not optimal for directing sound waves to the player's ear.