How do string instruments work

When two instruments are in tune, the beat frequency should be zero. This is an extremely useful tool for tuning instruments accurately by ear. Most people can usually tell whether an instrument is in tune or not without knowing the underlying science. Stringed instruments The pitch of a stringed instrument depends on the tension and the length of the string. In most stringed instruments the pitch gets higher when the player moves their hand closer to the bottom of the string making the vibrating area shorter.

However, Mike's double bass depended on changing the tension of the string to obtain each note. In many stringed instruments, the strings themselves only produce a small fraction of the sound that is heard. The rest is due to resonance from the body of the instrument vibrating in sympathy with the strings. Mike's double base had a huge box and a long string which gave it a very low pitch. Wind instruments These instruments work by using vibrating columns of air that amplify an initial sound.

In all wind instruments, the length of the column of air determines the general pitch of the instrument. That is why the panpipes played by Ellen used bamboo tubes cut to different lengths to produce various notes.

In order for a column of air to vibrate, something must start it going. The small sound produced by blowing over the top of each panpipe tube is greatly amplified within the tube, in much the same way as the body of a stringed instrument amplifies the sound from the string.

Percussion instruments The sound of a percussion instrument comes from striking two things together. They can be the simplest type of instrument because usually very few parts are needed to produce an amplified sound.

Our scientists made some drums from old barrels. When struck, the skin of the drum vibrated and was then amplified by the barrel to give out a sound. We've seen that musical notes can be explained using science.

We can even predict how to make notes using scientific equations but this doesn't help scientists to become better musicians! This article was inspired by the work of our Rough Scientists as they attempted to create music as part of the Rough Science Cariacou series. The Soundry - an educational website about sound.

Alexander Kolassa looks at how we hear music and discusses the categories which musical instruments belong to. Dr Robert Samuels explores looping in music and demonstrates how technology can make musical use of the sound of a dog eating a carrot.

Whether you're a professional musician, play music with your friends on the weekends or just like to listen to CDs, music technology affects your life. In this free course, Sound for music technology: An introduction, you will learn some of the basics of music technology, starting with what sound is, how it is created and how it travels. This free course, Recording music and sound, provides an historical introduction to music and sound recording in the creative industries and offers some guidance about making your own recordings.

Many of the processes that have been developed and the issues that have been raised in the first years of recording are still relevant today, and a solid grounding in them will help you understand the wide range of recording techniques currently in use. Globovision under CC-BY licence.

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Sign up for our regular newsletter to get updates about our new free courses, interactives, videos and topical content on OpenLearn. Studies like this allow us to understand instruments better, so that artists can make best use of their characteristics and instrument designers can build more innovative instruments. Physics of Stringed Instruments Gordon Ramsey — gpr anl. The top shows one-half complete wave between the ends.

The second shows one complete wave two halves between the ends, etc. One full wave has an effective length, called a wavelength. The note that is heard disturbs the air at a rate called the frequency. The wavelength and frequency are inversely proportional. The shorter effective wavelength corresponds to a higher frequency. The string player changes the note by changing the effective length of the string. The waveforms in Figure 1 represent multiple frequencies, called harmonics.

Instruments emit multiple harmonics with different strengths, which give each instrument its unique sound. Although one actually hears the note that corresponds to the fundamental first harmonic, the brain interprets all the harmonics as a recognizable instrument.

Figure 1. Harmonic waveforms. Figure 2. Experimental setup. Figure 3. Measurements of the mandolin. The procedure was repeated for the twelve instruments we studied. We analyzed the waveform harmonic structure see Figure 5 for an example , revealing the characteristic frequencies and corresponding intensities of the particular instrument.

Figure 4. Strummer measurements. These were placed at different locations: the octave half string length , the normal position and the bridge about one third and one fourth the length from the bridge, respectively. Along with string resonances, the bodies of stringed instruments also vibrate. Our examples exhibited different body shapes. We studied these body oscillations by distributing sand on the body of an acoustic guitar figure eight , dulcimer peanut , mandolin teardrop , and strummer triangular.

These instruments have a flat body, so when excited, the sand distributes itself in the places that are not vibrating. An oscillator was placed against the body to induce vibrations in the instrument.

As the frequency increased we observed how the sand patterns formed and related them with the string data. The dulcimer resonances are shown below. The one connected to the strings vibrates and creates sound, like a large speaker. Some of the sound is directly projected outwards while some of it is directed to inside the body.

The sound inside the body can reflect off the parallel surfaces and come out the sound hole s - this sound is fuller and darker, strengthening the fundamental frequencies played as well as balancing the overall frequency response of the instrument.

This is due to the size of the body, which is large enough for high frequencies to cancel out as they reflect, while lower frequencies do not. The relatively small size of the sound hole forces the sound to reflect inside the body before leaving, where it can form constructive harmony, preventing it from sounding thin. In electric instruments, the body serves simply as an anchor.

Thus, we see lots of types and weights of wood used, as well as body shapes and sizes in electrics. Pickups are used to convert the string resonance into electrical current, which is then sent to an amplifier which drives a speaker.

There are also acoustic-electric instruments that are essentially acoustic instruments with added pickups. Strings can be excited in a variety of manners. For guitar, the strings are typically excited with a plectrum pick or plucked with the right-hand fingers, but can also be slapped or hammered-on.