Sound Quality: Definition, Differentiation & Noise
When you go to a concert, your ear can pick out different sounds. You might hear notes being simultaneously played by a piano, guitar, and violin. Each of these instruments will sound different to you, even if they have the same pitch and loudness. So, how does your brain distinguish between different sounds? The answer has to do with the timbre, or the quality of the sound. Timbre is a general term used to distinguish one sound from another. In this lesson, we will learn about sound quality and how you use it to differentiate sounds and noises.
Regardless of whether you are talking about the pleasing sounds coming from a concert band, or the annoying sounds being generated by the person sitting next to you, we can think of sounds as a mixture of sound waves occurring at different frequencies.
As sound waves travel toward your ear, they alternately compress and expand the air. This movement of the air causes your eardrum to vibrate. The eardrum transfers this vibration to the small bones of the ear, turning the vibrations into nerve signals. From that point, your brain takes over interpreting the sound as pleasant music or annoying noise. So, we see that noise is largely a subjective phenomenon, which is really just something your brain considers to be undesirable sound. For example, a little girl playing a violin for the first time might sound like noise to you, but to her proud parents, it might sound like beautiful music.
Loudness & Pitch
Your brain recognizes different characteristics of sound. One easy characteristic to pick out is loudness, which is the strength of the sound. If we were to look at sound waves, we would be able to tell the loudness by the amplitude, or height of the waves. Basically, large amplitudes produce loud sounds. For example, a shout would produce a sound wave with a larger amplitude than a whisper.
Another characteristic of sound that your brain recognizes is pitch. Pitch deals with the frequency of sound wave vibrations. For example, a large instrument, like a tuba, produces low-pitched sounds that vibrate slowly, whereas a piccolo produces high-pitched sounds that vibrate rapidly.
However, loudness and pitch are not the only characteristics to consider when distinguishing between sounds. If the piano and guitar in our concert band play the same note at the same loudness and pitch, the sounds will be quite different.
That’s because the instruments vibrate at many different frequencies, not just one. These multiple frequencies are referred to as harmonics. The lowest frequency of sound waves is called the fundamental frequency. This is easy to recall if you think of something that is fundamental as being the most basic, or lowest level on which other things are built. The fundamental frequency, which is also referred to simply as the fundamental, also tends to be the loudest sound. The higher frequency harmonics are referred to as overtones. This is also an easy term to recall if you remember that something higher is overhead. The relative pitch and loudness of these overtones are what give a sound its unique quality or timbre, and what allow you to tell one sound from the next.
Let’s review. Whether you hear a sound as beautiful music or as an undesired noise is very subjective. We distinguish one sound from another through its timbre, or the quality of the sound.
Your brain recognizes different characteristics of sound, such as loudness, which is the strength of the sound, and pitch, which deals with the frequency of sound wave vibrations. However, to fully distinguish between sounds, we look to the relative pitch and loudness of the overtones, which are the higher frequency harmonics. These overtones are what give a sound its unique quality, or timbre.
After this lesson, you should be able to:
- Describe timbre
- Explain what noise is
- Discuss loudness, pitch and overtones