Three Components of Sound

Pitch Loudness and Timbre


Pitch is determined by how many times a sound wave repeats itself within one second of time.

  • Each repetition of a waveform is called a cycle.
  • The number of repetitions that occur per second is called the frequency.
  • Frequency is measured as cps = cycles per second or in Hz called hertz. “Hz” is derived from the name of Heinrich Hertz, a German scientist who did pioneering work in electromagnetic waves during the 19th. Century.


The Closer the peaks are together, the higher the pitch.

Human have a finite range of hearing

20 Hz to 20,000 Hz (20 kHz)
Ringtone Audible Only to Under-20 Year Olds
May 24, 2006 by Vurdlak

Wow!!! This has to be the coolest audio illusion of all times! Apparently, using the Mosquito device, UK pupils have recorded the ultra-high sound that is audible only to under-20-year-olds. Your hearing gets progressively worse around the age of 20, so if you play a sound on the edge of your hearing spectrum, unless you have perfect hearing, you won't be able to hear it at all. As I understood, the audio file is somewhere between 18KHz - 20KHz. When I played it, I haven't heard anything, and thought it was just another internet hoax, but then my 14 year old brother started yelling at me, to lower that sound cause it's driving him crazy - and he was in lower apartment!! Another thing.. my dog also flipped out! Here are some of these files. Check them out and report your findings!


  • The relative strength of the deviations in air pressure created by a vibrating object determines the loudness (or volume).
  • The greater variations in air pressure, the louder we perceive the sound.
  • These deviations are referred to as the amplitude of the waveform


The intensity level of a sound is measured in a unit known as the decibel (or dB). A unit of measurement named after Alexander G. Bell, who invented the telephone. The use of the capital “B” in the abbreviation is in his honor.

•The softest sound that a person can hear-the threshold of hearing”- is defined as 0dB.
•The “threshold of pain” is about 120 dB.




Harmonics Applet
Why does a flute sound different than a clarinet when they play the same note?
The number of harmonics present in their sound, and the relative amplitude of each harmonic.

  • The property of a sound that allows us to determine the difference between a saxophone and a flute is called timbre, or tone color.
  • Different timbres occur because most sounds actually contain many frequencies.
  • The predominant pitch is called the fundamental frequency of the sound. The other frequencies present occur in a mathematical series called the harmonic series, or overtone series.
  • The frequency of each harmonic is a whole number multiple of the fundamental frequency. (i.e.; 2x,3x,4x, etc..)

When a string vibrates to create a sound, it has several compressions and rarefactions occurring simultaneously.

The amplitude of each harmonic determines the timbre of the sound.


Creating different timbres electronically

Different timbres result in different shapes in the plotted waveform. Certain waveforms(and consequently certain timbres) have long been used a building blocks of synthesis.

A sine wave consists of only the fundamental. No other harmonics are present.

A square wave consists of only the odd harmonics.

A triangle wave consists of only the odd harmonics, however there is a decrease in amplitude of the upper harmonics.

Like a square wave, the triangle wave contains only odd harmonics. However, the higher harmonics roll off much faster than in a square wave (proportional to the inverse square of the harmonic number as opposed to just the inverse), and so its sound is smoother than a square wave and is nearer to that of a sine wave.

external image 350px-Synthesis_triangle.gif

A Sawtooth wave consists of all harmonics.


external image 400px-Waveforms.svg.png


All Frequencies combined create NOISE.

Most natural sounds form complex waves.


A moving sound object will catch up to itself... the waves then get closer together thus producing a higher pitch.
This is known as the Doppler Effect.
external image Doppler_effect.jpg