The Relationship between Pitch and Frequency

As I mentioned in the previous post, pitch is the subjective quality that determines whether something sounds low or high; differences in pitch are how humans distinguish the low sounding bass range from the higher sounding treble range, for example. Though pitch is a perceived property, it corresponds to a measurable property: frequency.

Frequency is the number of cycles in a wave over time. The most common unit of frequency and the unit used in the context of sound and music is hertz: cycles per second. The pitch of sound is defined by the frequency of its waves. In the context of music, the pitch of a sound is defined by its fundamental frequency, which is the loudest frequency it produces. Musical instruments also produce harmonics in addition to a fundamental frequency, which are waves of higher frequency that affect the timbre of the instrument.

Musical scales are tuned to the note A-440, which means that a central A note (for instruments tuned in the key of C) has a frequency of 440 hertz. The rest of the notes are tuned accordingly. This resourse is still a great tool to explore. Its default setting of 440 hertz should make perfect sense given the modern tuning system. You can change the number of hertz to explore how the pitch of the produced sound changes. Additionally, you can progressively double the number of hertz to hear the sound increasing an octave at a time, which is another important part of the relationship between frequency and pitch; doubling the frequency of a sound wave increases the pitch of the note produced by an exact octave.

Works Cited:

1. "Fundamental Frequency and Harmonics." Fundamental Frequency and Harmonics. The Physics 

Classroom. Web. 31 Aug. 2015. 

2. Gunther, Leon. The Physics of Music and Color. New York, New York: Springer, 2012.

3."Online Tone Generator." Online Tone Generator. Accessed August 26, 2015.

Qualities of Sound: Loudness, Pitch, Timbre

The three main qualities that are used to describe sound are loudness, pitch, and timbre. Loudness is pretty self-explanatory at a basic level; when you change the volume of your speakers or headphones, you change the loudness of the sound they produce. In the context of a sound wave, loudness is dictated by the amplitude of the wave, a measure of the highest (or lowest) point of a wave. You can explore this by using this resource from my previous post. After clicking oscillate in the top left corner, adjust the amplitude slider in the bottom right. A higher amplitude corresponds to a louder sound, and a lower amplitude corresponds to a quieter sound.

The easiest way to think of pitch is in the context of a musical instrument. In a piano, each key is tuned to a certain pitch and corresponds to a musical note. As you play each note on a piano descending from right to left, the pitch of the notes become lower. Pitch corresponds to the frequency of a sound wave, and my next post will cover this relationship in depth.

My previous post alludes to the concept of timbre (pronounced /'tambər/). I like to describe it as the quality of sound. Timbre is what distinguishes musical instruments; it is why they have a distinct sound even when playing the a note with the same loudness and pitch. The waveform, the shape of a sound wave, is what determines its timbre. This resource from my previous post illustrates this very well. By changing the waveform, you can hear distinct changes in the timbre of the sound without changing the loudness or pitch. Instruments are able to sound unique by producing sound waves with unique waveforms.

Works Cited:
1. Gunther, Leon. The Physics of Music and Color. New York, New York: Springer, 2012.

2."Online Tone Generator." Online Tone Generator. Accessed August 26, 2015.
3."Wave on a String." Wave on a String 1.0.0. Accessed August 26, 2015.

The Sine Wave & Sound Oscillation - The Foundation of Sound

The sine wave is the building block of sound. Simply put, sound is the vibration of particles in the air. As sound travels through the air, it compresses and pulls apart the air, which can be modeled well by an oscillating function; for example, a sine wave. This resource does a great job of modeling a sound wave as it passes through air. If you click the oscillate button, you will begin to see a sine wave. The peaks of the wave represent the most compressed air, and the troughs represent the opposite. Basically, a point above the line of equilibrium is more compressed, while a point below is less compressed. By adjusting the tension slider, you can visualize more complicated oscillations, which would produce distinct sounds. While some oscillations can look completely different from the sine wave, they are all derived from it, as shown by this model. This resource allows you to hear what a (nearly) perfect sine wave sounds like. By selecting different types of waveforms (square, sawtooth, and triangle), you can clearly hear how slight manipulations of the sine wave are able to change how sound is perceived. This video is a really helpful in visualizing this in the context of music; future posts will go into more detail about how the different aspects of sound waves are applied in music.

Works Cited:

1."Final Cut Pro 7 User Manual." Final Cut Pro 7 User Manual. Accessed August 26, 2015. 

2. Gunther, Leon. The Physics of Music and Color. New York, New York: Springer, 2012.

3."Iphone 4 inside a Guitar Oscillation! VERY GOOD!" YouTube. Accessed August 26, 2015. 

4."Online Tone Generator." Online Tone Generator. Accessed August 26, 2015. 

5."Wave on a String." Wave on a String 1.0.0. Accessed August 26, 2015.