Acoustics as a Design Priority

Why is it so important to have an acoustic specification as a design priority? The short answer is that in the great game of tradeoffs in system design, low acoustic emissions don’t just “happen” unless there is sufficient value placed on them. There are too many other things that seem more important: size, weight, and cost, among other things. Small size in particular is a big challenge to getting a quiet system; it tends to push objects into close proximity to fans, whose aerodynamic performance suffers as a result. It also tends to reduce free space for air movement, which produces high system flow impedance. The traditional rule of thumb for power supply designers says that if you can fit the eraser end of a pencil between components, your design is too big! I’ve also found that most mechanical engineers are used to thinking in terms of solids; after all, it’s what they’re designing and producing. It’s a big shift for them to think in terms of the space that’s left over between their parts: you can’t see it, touch it, or rotate it in your CAD system. Yet that very space completely governs the system flow paths, and is therefore a key contributor to acoustic noise.

But it’s not only the engineering team that needs to keep acoustics in mind as a design priority; the priority needs to go back even further in the design process to the marketing team. These are the folks deciding what the engineering team is supposed to make. Or rather, they’re the ones trying to figure out what they think they can sell about a year from now. Only when they decide that quiet systems will sell better will there be sufficient priority placed on acoustic noise emission during the design phase.

With noise as a priority in the design criteria, it will get the attention it deserves. But it’s often not clear even to the engineering team what tradeoffs affect noise emissions.