Reading 2

Unit 4- Reading 2

Page 56

Guitars: the quest for volume

Today, people tend to think of the guitar as a loud instrument. Yet, before the 1920s, projecting sound was a problem for the guitar. The volume was simply too low to compete with louder instruments, limiting its use to solo performance and vocal accompaniment.

The versatility and portability of the guitar, however, were simply too appealing to allow it to drift into obscurity. Guitar makers began experimenting with new designs and materials that could increase its volume.

To understand the fundamental challenge facing guitar designers, first consider what a guitar is trying to do.

A guitar operates on the principle that a tightly stretched string, when plucked, will vibrate rapidly and agitate the air enough to make a musical tone that people can hear. The shorter, tighter, and thinner the string, the more vibrations per second and the higher the pitch of the tone. The longer, looser, and thicker the string, the lower the pitch.

So by plucking strings of various thicknesses, tensions, and lengths, a variety of musical notes can be created.

But there’s a problem. A vibrating string does not make much sound. It needs to be made louder, or amplified, in some way. Try this grade-school experiment: Wrap a small, thin rubber band around your thumb and index finger. Stretch it tight and pluck it.

It will make a sound but not a loud one, and the volume will diminish quickly. Now stretch the rubber band around a small, thin-walled box with one open side. Pluck the string where it crosses the opening. A much louder, longer sound should result. That is because the string vibrates the box, which in turn vibrates the air inside the box and creates a sound.

Because the sound can echo a bit, it also sounds fuller—that is, it has a better tone. So, a thin box with an opening makes a rather good amplifier for strings.

A guitar takes advantage of box amplification by attaching a long piece of wood—the neck—to the hollow guitar body, or sound box.

The strings run down the neck to the middle of the body to a piece of wood called the bridge. The bridge has two purposes. It anchors the strings to the guitar top (also called the soundboard). It also contains the saddle, a thin piece of hard material that lifts the strings slightly above the neck and top. When the strings are plucked, the saddle transmits the vibrations into the guitar body.

The wooden sides of the body vibrate the air inside and create an echo that increases the volume of the original vibration. The sound exits through one or more sound holes cut into the top of the guitar.

The shape and dimensions of the guitar body are important in making sure that the vibrations from the different strings are amplified fully and equally. Guitar designers experimented with many different designs.

After much refinement, they found that a figure-eight shape with a larger and a smaller chamber separated by a narrower waist works best. This shape best amplifies and smoothes the sound of all the tones that a guitar can make.

Even with this optimal design, a guitar made entirely of wood is not very loud. Guitar designers faced an intrinsic difficulty in the physical properties and design of a guitar.

Heavier, tighter strings are louder. Thinner wood is also louder. But heavier, tighter strings place tremendous stress on the guitar, requiring thicker wood to strengthen the guitar and keep it from breaking. So the increase in volume gained by using heavier strings and greater tension is offset by the thicker wood needed to strengthen the guitar. Guitars, it seemed, would never be loud.

In the early 20th century, the search for a louder guitar intensified. Two solutions appeared. One design strengthened the guitar by running a metal rod through the neck of the guitar and by adding more support in the bridge area. This way, louder steel strings could be used without damaging the guitar. Today, these design improvements are incorporated into most hollow body, steel-string guitars.

The second solution added metal resonator plates to the top of the guitar to take advantage of the “twangy” acoustic properties of metal. The twang not only made guitars louder, but the change in tone helped them stand out more when played along with other instruments.

With these modifications and added features, guitars could be heard more easily, but they still could not fill a large building with sound.

Here is where advances in electronics play a role. One possibility, of course, is to put a microphone in front of the guitar. In theory, this works well enough. In practice, it can create several problems. The microphone limits a player’s movements, and it often picks up other sounds, amplifying them along with the sound of the guitar.

Even when everything works perfectly, the core problem remains: the guitar itself is not any louder.

Achieving a true electric guitar required a complete rethinking of how a guitar could work. Rather than have the guitar body amplify the sound, the body would merely be a platform that holds vibrating strings—similar to those on an acoustic guitar—and electronics. The body could even be solid, not hollow.

With a solid body, the strings make a very soft sound— softer than the sound achieved in the rubber- band-around-the-box experiment, and not nearly enough to amplify successfully through a typical microphone. Instead of a hollow sound box, the strings are placed just above tiny magnets, or pickups. When the strings vibrate, they create a weak but precise disturbance in the pickup’s magnetic field.

That disturbance (the audio signal) is transmitted as a weak electrical current through wires and cables to an electrical device that amplifies the signal through a speaker, sometimes to ear-splitting levels. By the 1950s, electrics were revolutionizing popular music.

Meanwhile, efforts were being made to electrify what were now called acoustic guitars—the steel string guitar made of wood.

Amplification is achieved by placing pickups inside the guitar body. These pickups contain a mechanism (a piezo-electric transducer) that is sensitive to vibration. They transmit an electrical version of the vibration through wires to an amplifier. The thinking here is that by capturing body vibration, the amplified sound will have a more natural tone, and it does.

There are many competing designs, and the technology is constantly changing, but whatever their form, internal pickups allow traditional acoustic guitars to achieve greater amplification while maintaining the acoustic guitar sound.

Electronic amplification opened the door for musicians to experiment with sound in other ways. Before sound can be amplified electronically, it must be converted into an electronic signal, and this signal can be modified to achieve different effects.

Think of it this way: the volume and tone of an acoustic guitar are mainly the result of its materials and design. A well-designed acoustic guitar made of good materials sounds better than a less carefully constructed one. With a solid body electric guitar, however, the electronics build and shape the instrument’s naturally thin tone by enriching the audio signal before it is transmitted to speakers.

After decades of research and development, guitar players can now manipulate and modify the audio signal in the most astounding ways. Just consider the colorful vocabulary they use to describe the sounds of an electric guitar— crunch, punch, fuzz, Hange, wah wah, chorus, screaming, delay, gated. Some of the possibilities are quite unpleasant.

Others add to the library of wonderful sounds that are used to make music. These acoustic gifts are the unexpected but natural consequence of the long effort to do one simple thing—to make a very mellow instrument a little bit, or a whole lot, louder.