properties+of+sound

HUMA 2104 - Intro to Music Theory

Week One Lecture

Tuesday, September 3, 13

What is Sound?

Vibrations transmitted through an elastic medium that are able to be detected by the human ear.

These vibrations are actually rapid fluctuations in the average atmospheric pressure where the sound is heard.

Rarefactions - less than standing air pressure

Compressions - greater than standing air pressure!

Radiates in a sphere from the source - Surface area of sphere = 4(pi)r^2,

When these fluctuations in air pressure reach us, they cause sympathetic vibrations on our eardrums.

Tuesday, September 3, 13

The four basic properties of sound

Frequency Amplitude Duration Location

Tuesday, September 3, 13

Frequency - periodic waveforms

What we perceive as pitch is the result of a periodic waveform.

A waveform is a pattern of pressure variations produced by a sound expressed as cycles per second (cps)

Non-periodic waveforms are perceived as noise. In notation, frequency (pitch) is represented by vertical

position on the staff. The range of human hearing is ideally 20 - 20,000 cps The range of the piano is 27.5 - 4186.1 cps

Tuesday, September 3, 13

Frequency Vs. Pitch

Throughout history, music of the west has been based upon simple frequency ratios.

The most basic ratio (1/2) forms the octave, which is the basis for our scale systems.

Lets take a look at a periodic waveform in action.

Tuesday, September 3, 13

Amplitude

l The amplitude of a waveform is the amount of change, positive or negative, in atmospheric pressure caused by the compression/rarefaction cycle of a sound wave.

l In rough terms, we perceive this degree of change as loudness or intensity.

Tuesday, September 3, 13

Duration

This one is pretty self-explanatory In notation, duration is indicated by

rhythmic values.

Tuesday, September 3, 13

Location

Well... There isnt really a standard way to notate this one.

Flute

Tuesday, September 3, 13

Location

Well... There isnt really a standard way to notate this one.

Flute

Climb inside the piano

Tuesday, September 3, 13

Timbre

Timbre is often considered to be a fifth basic property of sound in musical contexts.

However, it is actually just a combination of frequency and amplitude that we perceive as a sources sound quality.

Lets take a closer look on the sonogram.

Tuesday, September 3, 13