Harmonics

Harmonics

Each instrument has a mixture of harmonics at varying intensities

Principle of superposition

Periodics- Repeating patterns of waveforms

Harmonics

Characteristics of an instrument is referred to as its SOUND SPECTRUM

TIMBRE- means sound quality

Timbre or Quality of Sound

Instruments do not vibrate in a single mode.Several harmonics are produced at the same time.

The particular harmonics and intensity of each vary with different instruments.

Timbre is the quality of the tone resulting from the combination of harmonics.

The fundamental frequency (1st harmonic) determines the pitch.

Adding other harmonics changes the timbre.

Timbre

Harmonics

Intensity of an instrument depends on a variety of factors

For example a violinWhere the string is bowed

The speed of the bow

The force the bow exerts on the string

Fundamental Frequency

Determines the pitch

Subsequent harmonics are referred to as OVERTONES

The second harmonic = the frequency of the next octave

BeatsThe diagram shows two waves of different frequencies. Sketch the superposition or sum of these waves.

How would the combined wave sound?

Initially destructively….then constructively…..back to destructively

Beats

Interference of waves of slightly different frequencies traveling in the same direction

Perceived as a variation of loudness

Beats

Out of phase

Waves opposite each other

Destructive waves

Equals no SOUND

Beats

In phase waves

Waves that coincided with each other

Constructive waves

Sounds louder

Beats

Number of beats per second = the difference between two frequencies

Example:A piano tuner using a 392 Hz tuning fork to tune the wire for G-natural hears four beats per second. What are the two possible frequencies of the vibration of this piano wire?

Beats

Produced by two waves with the same intensity and different frequencies

Generally the frequencies are nearly the same.

The sound pulses or changes from loud to soft and back.

Beats are used to tune instruments.If a tuner hears beats, the instruments are slightly out of tune.

The number of beats heard per second is the difference in the two frequencies.

Click below to watch the Visual Concept.

Visual Concept

Beat