I’ve been trying to understand how sound works, and this part really confuses me. If pitch and intensity are all that determine the wave that our ears process, how do we perceive so many different kinds of sounds?
In: Physics
Pitch and intensity are not all that determines the wave that our ears process.
Our ears very, very rarely process a “single wave.” And even less rarely do those waves we hear only change in amplitude (an important part of loudness and “intensity”) over time.
Our ears hear complicated sounds and break them down into simpler waves – sine waves. Then, our ears process exactly how the simpler waves that make up a single “sound” are related to each other and how those simpler waves change over time. That is a lot of how we hear differences in sound besides intensity and pitch. But this is still a matter of study both by scientists and artists.
Pitch is a property of our human hearing more than it is a property of sound. Most sounds are a collection of many different frequencies (“pitches”, though not exactly the right word), and there’s many many different ways we could combine different frequencies.
It just happens that many sounds are harmonic (the frequencies are related in that they are all part of the same harmonic series) so we’ve learned/evolved to hear the entire thing as one sound with one pitch, since all those frequencies are usually from the same sound source and rarely rogether by coincidence.
A ‘pure’ tone is a sine wave with a single frequency and volume. Most sounds aren’t pure sine waves. Instead, you can think of them as a bunch of sounds played on top of each other. The different sounds have frequencies that are all multiples of the ‘main’ frequency so they all stay ‘in sync’ with each other and sound like one pitch. For one particular sound, the volume of each of the different component sounds can vary, and that’s what makes a saxophone and a violin sound different when they play the same note. The technical term for analyzing these different component sounds is ‘fourier decomposition’
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