Why Do Instruments Sound Different?
It's Going Down, I'm Yelling Timbre
There are so many instruments like the piano, violin, and guitar, and each and every one of them creates a recognizable sound. If you play a similar song on a different instrument, you will directly hear the difference. What causes this? What gives instruments their unique sound?
A Definition of Sound
Let’s start at the beginning: what is sound? To create sound, you need vibrations. These vibrations create air movement. When we are able to hear those waves, it’s called sound. Two terms often used to describe sound are frequency and amplitude.
Frequency tells us something about the height or the pitch of a sound. It’s the number of waves completed per second. The higher the frequency, the higher the sound. Frequency is expressed in Hertz. We human beings can only hear acoustic waves that have a frequency between 20 HZ and 20 kHz.
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. Speech, for example, is 60 dB and music 80 dB.
Notes and Overtones
The next thing you should know more about is tones and overtones. When you play a note, you actually play several (softer) notes with different frequencies. When playing 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 one 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 start to answer our main question: what makes instruments sound unique? Instruments have different timbres or tone colors. Timbre is a word often used to describe the sound quality of an instrument.
The reason instruments have a unique timbre is because every instrument creates a different set of overtones. Remember when playing a note more notes are created with a higher frequency? The amplitude of the overtones that instruments produce differ which makes instruments sound different.
Generally, instruments that create lower sounds like cellos can produce more audible overtones than instruments that create higher sounds like violins. Because the strength of the sound levels of the overtones that each instrument creates 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 but also the way you play an instrument have a huge impact on the sound quality of an instrument.
The design of an instrument determines how vibrations or sound waves are amplified through 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 influences the vibration patterns when a violin is played. These patterns create certain overtones which make a violin sound unique.
The way you play an instrument also influences how you perceive sound. For example, if you play a note at the beginning of a string, it can sound way louder than when you play it at the end of the string. Why? Because the amplitude of the overtones is different at other parts of the string.
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. If you pluck a string on the violin, for example, you reach a faster attack and decay than when you play the violin with a bow. This way you create a whole new sound experience with the same instrument.
It feels so obvious that instruments sound different, but the reason behind it is actually quite complex. It’s mind-blowing that you actually produce many different tones with different frequencies when playing one note. The fact that the loudness of those extra tones makes instruments sound unique is fascinating. Such a delicate difference, which can be influenced by design and technique. It makes playing an instrument even more interesting.
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