Why Do Instruments Sound Unique?
It's Going Down, I'm Yelling Timbre
A definition of sound
Let’s start at the beginning: what is sound? To make sound, you need vibrations. These vibrations create air movement. If we can hear these waves, we call it sound. Two terms often used to describe sound are frequency and amplitude.
Frequency
Frequency says something about the height or pitch of a sound. It is the number of completed waves per second. The higher the frequency, the higher the sound. Frequency is expressed in Hertz. We humans can only hear acoustic waves with a frequency between 20 Hz and 20 kHz.
Amplitude
Amplitude is the strength or level of sound pressure. The higher the pressure, the higher the amplitude. And the higher the amplitude, the louder the sound. Amplitude is expressed in decibels. For example, speech is 60 dB and music is 80 dB.
Notes and Overtones
The next thing you need to know more about are notes and overtones. When you play a note, you are actually playing several (softer) notes with different frequencies. When you play an A, you create a sound wave with a frequency of 440Hz. This is called the first and fundamental harmonic or tone. But you also create a second sound wave that is twice as fast (880Hz), called the second harmonic. And you also create a third that is three times as fast (1320Hz) and so on. These extra tones with higher frequencies are called overtones or harmonics. The different sound waves together are called “The Harmonic Series.
Timbre: a Unique Set of Tone Colors
Now that you know more about sound and notes, we can begin to answer our main question: what makes instruments sound unique? Instruments have different timbres. Timbre is a word often used to describe the sound quality of an instrument.
The reason instruments have a unique timbre is because each instrument creates a different set of overtones. Remember how playing a note creates more notes with a higher frequency? The amplitude of the overtones that instruments produce differs, making instruments sound different.
In general, instruments that make a lower sound, such as cellos, can produce more audible overtones than instruments that make a higher sound, such as violins. Because the strength of the sound levels of overtones each instrument produces is different, instruments have their own timbre.
What Influences Timbre?
So instruments sound different because of their unique set of overtones. But what influences the amplitude of overtones? The design of an instrument, as well as how you play an instrument, have a huge impact on the sound quality of an instrument.
Design
The design of an instrument determines how vibrations or sound waves are amplified by the instrument. What material is used and what is the shape of an instrument? This is why even two violins can sound different. The unique backplate of a violin affects the vibration patterns when a violin is played. These patterns create certain overtones that make a violin sound unique.
Playing technique
The way you play an instrument also affects how you perceive sound. For example, if you play a note at the beginning of a string, it may sound much louder than if you play it at the end of the string. Why? Because the amplitude of the overtones on other parts of the string is different.
Skilled musicians can use certain techniques to create unique sounds. They influence how the sound develops over time. There are four stages of sound: attack, decay, sustain and release. For example, if you pluck a violin, you achieve a faster attack and decay than if you play the violin with a bow. In this way, you create a whole new sound experience with the same instrument.
Final Thoughts
It seems so obvious that instruments sound different, but the reason behind it is actually quite complex. It is amazing that you actually produce many different tones with different frequencies when you play one note. The fact that the loudness of those extra tones makes instruments sound unique is fascinating. Such a delicate difference that can be influenced by design and engineering. It makes playing an instrument even more interesting.
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