Sound Waves
All sounds are generated by vibrations and travel as sound waves through a listening medium. This medium is composed of the vibrating molecules that transfer sound waves throughout physical space. In a wide open areas the listening medium is usually air, and the air molecules vibrate as sound waves travel through them. However, the listening medium doesn't have to be air, and can be any substance capable of vibration such as: wood, string, water, or crystal.
​
Sound originates from a specific source and propagates outward through the medium in the form of sound waves. These sound waves do not carry the particles of the medium but merely vibrate them, causing them to collide with one another to spread the sound wave. Eventually the sound wave will disperse when it not longer has the energy to excite nearby particles. See below how sound waves propagate outward from the initial source.
The image above and to the right depicts the two features of a wave that define sound: the amplitude and the frequency. The amplitude of a wave is the vertical distance from the center of the wave to its peak. The greater the amplitude the greater the volume of sound that is produced by the wave. A wave's frequency determines the pitch of a sound. Waves comprised of higher frequencies produce sounds of a higher pitch while lower frequencies produce sounds of lower pitch. Therefore, low pitched sounds are generated by slower waves with longer wavelengths while high pitched sounds are generated by faster waves with shorter wavelengths.
​
Sound waves can also combine with one another to produce new waves. If the sound waves align in frequency then they can combine to reinforce one another. In this case, the amplitudes of each wave will add together and the sound waves will combine to produce a much louder sound of the same frequency. Sound waves whose frequencies don't align are considered to combine destructively and their energies will conflict to weaken each other. The waves may cancel each other out or could combine to produce a weaker sound depending upon the combination of the added frequencies.
The three most common descriptors of sound are dark, bright, and brilliant. Each of these qualities of sound is unique and is attributed to variations in the sound waves forming the sound. Any sound is initiated as a fundamental pitch, the original tone from which all the resulting sound is formed. In response to the fundamental pitch a collection of overtones is also produced, tones with pitch at a higher frequency than the fundamental pitch. As overtones go higher in pitch the intervals between their frequencies become smaller and the pitches occur closer together. The collection of specific pitches that play from a fundamental pitch is unique to every sound and provides timbre, the unique character and quality of sound that identifies the source of the sound. Timbre allows us to recognize the differences between sounds, for example, instantly recognizing that a piano is different from a trombone, even if they play the same pitch, or recognizing a familiar voice. Different sounds possess different collections of overtones that produce unique timbres.
​
Dark sounds are those whose lower overtones (just above the initial pitch) have a greater amplitude than the fundamental pitch. We hear a collection of lower-pitched tones which combine together to produce a darkly textured sound.
​
​
​
​
​
​
​
​
​
​
​
​
​
​
​
​
​
​
Bright sounds originate in much the same manner as dark sounds, but are comprised of higher overtone pitches. Overtones much higher than the fundamental pitch are more present, having a greater amplitude. Bright sounds are often described as having a more brittle texture because their frequencies are spaced over a smaller area due to the rise in pitch.
​
​
​
​
​
​
​
​
​
​
​
​
​
​
​
​
​
​
​
A brilliant sound is one which extends through the entire range of producible overtones. After the fundamental pitch, all overtones are supplied and resonate with great amplitude to produce a full spectrum of sound. Brilliant sounds often "ring" within our ears because the collection of overtones and their resonance is so great that we hear the overtones louder than the fundamental pitch.
​
​
​
​
​
​
​
​
​
​
​
​
​
​
​
​
All instruments have a vibrating mechanism as well as a means to amplify the sound so that it can be more easily heard. On a violin the vibrating mechanism are the strings, which vibrate and transfer their vibrations through the bridge into the belly of the instrument. This area resonates well and amplifies the sound of the strings, producing a louder sound whose sound waves can carry much further than those of solely the strings.
​
​
​
​
,
Click either of the buttons to the right to visualize your own sounds using a spectrogram. The spectrogram provides a visual graph of the frequency of sounds, allowing you to "see" what a sound looks like. Examine provided sounds or upload your own recordings!
Darkly textured sounds are often described as thick and warm. Notice in the above videos how compact the frequencies are. This densely layered sound provides a deep and rich texture, which is seen in the concentrated group of lower frequencies. The video to the left is a recording of a natural wooden cello while the video to the right is a recording of a carbon fiber cello.
Brightly textured sounds are usually described as being thin and insubstantial. Notice in the videos above that the resonating overtones are very sparse, creating a sound that lacks body. This is characteristic of a bright sound. The video to the left is a recording of a natural wooden cello while the video to the right is a recording of a carbon fiber cello.
Brilliant sounds are full and resonant, having equal projection of overtones. Notice that the overtones above the fundamental pitch (second lowest frequency) all appear at nearly the same intensity, if not with greater intensity, than the fundamental pitch. These relationships among frequencies produce brilliant sounds. The video to the left is a recording of a natural wooden cello while the video to the right is a recording of a carbon fiber cello.