Acoustics

Through out the air, there are many submicroscopic units called molecules. The molecules are able to move freely, yet always stay a certain distance apart from each other. However, sometime the molecules are forced to get close together. This causes them to bump into one another, making them fly back apart. This is what is considered elasticity. When the molecules are forced to come together, or compressed, the elasticity of the molecules create a compression wave. When the molecules receive extra space, and expand into the space, the elasticity of the molecules create a rarefaction wave. These two waves travel to the ear drum, which is then transmitted to the brain. If the waves are irregular, we will perceive it as noise. If the waves perform a pattern that repeats itself regularly, it will be perceived as a musical tone. The simplest musical tone will have a pattern of compression, rarefaction, compression, rarefaction, at a consistent frequency. These vibrations are considered to be like a pendulum, because they repeat themselves, like the swing of a pendulum. The vibrations of these compression, rarefaction waves create a cycle. Depending on the frequency at which these waves vibrate, a certain pitch will be created. Pitches are measured in cps (cycles per minute) also known as hertz.

There are five Properties of Musical Tone/Regular waves

Pitch is measured by cycles of compression, rarefaction waves vibrating at different frequencies of speeds. For example, an “A” on the treble staff vibrates 440 times a second. If we were to double the vibrations of that A, the ear would hear an octave higher than the “A” on treble clef.

Duration is how long the tone lasts. Without duration, there is no rhythm

Intensity consists of how much the molecules were compressed. Intensity occurs when molecules hit each other at a greater force. If the intensity is increased, we perceive loudness to increase. High tones often sound louder than low tones even at the same intensity, because our ears are more sensitive to high tones. Intensity doesn’t necessarily mean loudness, however. A singer can sing with intensity without being loud. Tones that lack intensity are usually breathy. Therefore, intensity can mean more energy in the tone.

Timbre is the complexity in a vibration or cycle or the enhancing and suppressing of certain partials. A timbre will create the fundamental pitch, which happens to be the lowest frequency, or fundamental pitch we hear. Within the fundamental pitch, other significant frequencies are produced call overtones. Overtones include harmonics or partials. If we were to listen to a certain timbre, we may be able to pick up different pitches that vibrate within the fundamental pitch.

Sonance is an irregularity in the midst of a pitch. It is considered as noise. For example, a consonant is considered as a Sonance. Sonance has color or quality to it, and can be confused with timbre.

* This was taken from my studies of Acoustics from William Vennard