If you already have a great grasp top top what sound is on a physical level, you have the right to feel free to move on come the following section. If girlfriend are new to the scientific research behind sound, or just want a refresher, this section will briefly explain the two main aspects behind every sound we hear.

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For a more in-depth explanation the audio basics, check out this Audio college article. That goes into much more detail and also contains animations that are advantageous for visualizing sound waves.


Frequency is very closely related come pitch. Typically speaking, high-pitched notes room high in frequency and also low-pitched notes space low in frequency. If you’re new to the concept, you could be asking, “Frequency the what?”. 

Every sound us hear is a series of vibrations. Let’s take a loudspeaker because that example.

When no sound is being sent out through the speaker, the rests in that default position. Us will speak to this starting position “0”. Once an audio signal is sent to the speaker, that starts to push outward and also pull inward. You have the right to see this in the following image.


You deserve to see a much an ext detailed computer animation of how a speaker functions by Animagraffs. This is a website the creates exceptional 3D models of assorted technologies.

As a speaker vibrates forward and backward, that displaces the air particles in the atmosphere. This creates a chain reaction through the air from the speak to our ears. 

Each time the speaker moves from the default position, to the front position, to the backward position and returns come the default position, one bike is completed.

Frequency is the variety of cycles completed per second. That is measure in Hertz (Hz). 

The complying with image mirrors one bicycle of movement represented on a graph.


The frequency the the musical note A is 440Hz, meaning the cycle over is perfect 440 time per second when this note is played. This is the A in the center octave the a piano, referred to as A4. The frequency that the A in the next octave up is 880Hz. This pattern continues with each octave: 440Hz, 880Hz, 1760Hz, 3520Hz, 7040Hz, and so on. 

The frequency that a keep in mind doubles through each octave. 

This graph mirrors a frequency together with its first octave.



The amplitude of a sound identify the pressure of the sound wave. Typically speaking, the greater the amplitude, the louder the sound. 

In the examples above, the amplitude of the wave is an arbitrarily unit the 1. Amplitude is measure in pascals, a unit of pressure.

For the purpose of this post, that is only essential that you know the relationship between amplitude and loudness.

If you want to gain a an ext in-depth knowledge of this concepts, review this post about how sound works and the nature of a sound wave.

Why Do instruments Sound Different?

The exact same sheet of music play by a different instrument will certainly sound radically different, also though the same notes are played. This is since each instrument has its own unique tone, or timbre. 

In this section, us will discover the facets that make up an instrument’s timbre.

The Harmonic personality Of The Instrument

Harmonics space overtones created when a note, or frequency, is played. 

When the musical note A is played on one instrument, a sound tide is produced with a frequency the 440Hz. This is the basic frequency, or very first harmonic. 

Harmonics room calculated by adding the an essential frequency to chin again and also again. 

The 2nd harmonic that 440Hz is 880Hz, one octave over the fundamental frequency (440Hz + 440Hz = 880Hz). The third harmonic of 440Hz is 1320Hz (440Hz + 440Hz + 440Hz = 1320Hz). The bike continues, adding the an essential frequency each time:

Fundamental (1st Harmonic)440 Hz
2nd Harmonic880 Hz
3rd Harmonic1320 Hz
4th Harmonic1760 Hz
5th Harmonic2200 Hz
6th Harmonic2640 Hz
7th Harmonic3080 Hz
8th Harmonic3520 Hz
9th Harmonic3960 Hz
10th Harmonic4400 Hz

Each instrument the vibrates in ~ 440Hz will likewise vibrate at these exact same harmonic frequencies. The difference between instruments is how loud every harmonic is in comparison to the basic frequency. 

The complying with graphs show the frequencies produced when the same keep in mind is play on miscellaneous instruments. Notice that the same frequencies space present, however the intensity of these frequencies varies relying on the certain instrument.


Why do Harmonics Exist?

Fundamental and harmonic frequencies are determined by the dimensions of a sound source. 

This have the right to be interpreted visually utilizing the photo of a etc string.

As the string vibrates at its an essential frequency, it is organized in location at every end. There is no activity at the nodes and also the greatest motion in the antinodes. The vibration at each frequency is represented in the adhering to images.

In reality, strings vibrate at every one of the complying with frequencies to differing degrees, simultaneously.

The harmonic sequence continues far beyond the third harmonic. 

Each harmonic different in amplitude. The distinct mix of this harmonic frequencies identify a string’s harmonic character.

The harmonic personality is what offers a etc string its distinct timbre.

The enlarge the harmonics, the brighter the sound. The quieter the harmonics, the duller the sound.

The sound differences between different acoustic guitars making use of the exact same strings, however, needs to do v the body shape and also density of the guitars. 

These factors, shape and density, recognize the harmonic character of every instruments. 

Take a look at the adhering to video. This is dubbed a Chladni plate.

A speak is placed below the plate, leading to the plate come vibrate at a certain basic frequency. Granules that sand space spread over the plate. The granules clear up in the part of the key that carry out not vibrate.

The Chladni plate enables us come visualize the harmonic character of in different way shaped plates! Check that out:

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OK… Let’s continue on come the other facet of one instrument’s distinctive sound – envelope.

The Envelope that The Instrument

In enhancement to a distinct harmonic character, every instrument has a unique envelope.

The envelope of an instrument describes the level variation of a note or chord over time. It is separated into three parts: Attack, Sustain, and also Decay. 

Although the envelope of one electronically synthesized tool is explained by attack, decay, sustain, and release, the function of this section is to explore the variables that recognize the envelope that acoustic instruments.


Attack is a measure of time. The represents the moment it takes a keep in mind to reach its best intensity. 

Instruments through short assault include percussion, piano, and plucked string instruments such as etc or harpsichord. When a keep in mind is play on these instruments, the sound conveniently reaches its best level. 

Instruments qualified of long attack include woodwinds, brass, and also bowed string tools such together violins. Note played on this instruments can start quiet and also slowly construct to their maximum level.

The adhering to graphs show a comparison between short attack and long attack:


Sustain is a measure up of time, in the paper definition of acoustic instruments. It to represent the expression of time that the steady-state intensity of a note is held. 

Snare drums, banjos, and also many various other percussive tools are instances of instruments with short sustain. When the keep in mind played and reaches its preferably intensity, it quickly starts to decay.

Instruments together as electric guitar, bowed string instruments, and wind tools are qualified of long sustain. The musician deserve to hold a keep in mind for a sustained period of time at a steady-state intensity.

These graphs present a comparison between short sustain and also long sustain:


Decay is a measure of time. It represents the duration of time a keep in mind takes to autumn from the steady-state strongness to finish silence. 

Most percussion instruments have a brief decay. The intensity of the note conveniently falls after that the sustain period. Even if the instrument has actually a long sustain time, it can have a short decay time. Because that example, a violinist have the right to hold a long, continual note and also then abruptly quiet the instrument.

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Cymbals room one instance of an instrument through a long decay time. ~ the early strike, the soot of a cymbal’s sound slowly drops until the is totally silent. Keep in mind that the musician play the cymbal can shorten the decay significantly by silencing the cymbal with his or she hand.