The Science of Sound

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Introduction

Sound is a compressional wave caused by the vibration of an object. Waves can travel as transverse or compressional waves, depending on the relationship between the movement of energy and the movement of the medium; if the medium moves at a right angle to the energy, it is a transverse wave, and if it moves in the same direction as the energy, it is a compressional wave.

Figure 1- a transverse wave and a compressional wave.

Qualities of a sound

Figure 2- a transverse wave, labelled.

Sounds can be differentiated from each other through identifying its qualities, such as pitch, amplitude, speed and timbre. Pitch is able to be determined by the frequency of sound waves, and is measured in hertz (Hz). It can be seen in a soundwave by measuring the distance two corresponding points in the same soundwave, or the wavelength. Humans can detect between 20-20000 hertz; sounds with pitches below this are called subsonic, and sounds with pitches higher are called supersonic. Pitch determines the way a note sounds. Due to the way we perceive sounds, pitches around 4000 Hz sound the loudest to a normal humans ear. Amplitude is a measurement of the loudness of a sound. Amplitude can be seen in a soundwave by measuring the distance between the crest (top) and the trough (bottom) of a soundwave. Amplitude is measured in decibels, (dB), a logarithmic scale from 0-140. 0 decibels represents the faintest sound which is able to be heard by humans, and 140 represents the sounds which leads to hearing loss in a normal human being. Amplitude can be seen in a wavelength by Decibels and hertz, together, determine the total power output of a sound at a distance, in the following equation.

Power = intensity X sphere aura

The intensit...

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...ply having more strings; 88 keys with 230 keys in a grand piano, in comparison to a violin’s 4, or a guitar’s 6-12.

Pianos.

Figure 4- grand piano.

A piano is a stringed musical instrument which is operated by a series of keys, which when pressed, signals to corresponding hammer mechanisms to drop upon the string. When the hammer is lifted The vibration of the string is amplified on the soundboard and released into the air. The piano is capable of playing 7 octaves, from a range of 27.5 Hz and 4186 Hz. Pianos have its setting changed using pedals; the left pedal shifts the keyboard so that less strings are struck during each key press, the middle pedal disengages the dampeners, which normally act to stop the strings resonating when the hammers are not on the string, and the right pedal increases the dampening on strings, making the individual notes more crisp.

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