Treating air as communicating cells explains propagation, reflection, and diffraction

Evidence

Imagine dividing air into small cells. Each cell is large on the molecular scale; they are packed one next to the other. The size of the cell is determined by the wavelength of the sound involved (there needs to be at least several cells per wavelength) and the details of any obstacles, sound sources, and so on. If we can understand how the cells communicate with each other, are pushed by and then push back on neighboring cells, we can understand propagation, reflection, diffraction, and even refraction of sound. This is our first glance at a powerful engineer’s trick, wherein the properties of complex objects are lumped into a few well-chosen summarizing properties. These have vastly less information than the original system, but enough to carry the essential physics, and lead more easily to the correct conclusions. — Eric J. Heller, Why You Hear What You Hear- An…, 58

Categorization

• DEFINE: Introduces the lumped-parameter engineering framework the book will use throughout.
• XREF: The lumped-summary trick parallels the coarse-graining idea in thermodynamics and statistical mechanics.