Managing the Testing Process: Practical Tools and Techniques for Managing Hardware and Software Testing

A.9. Acoustics

Systems with built-in speakers and microphones are supposed to reproduce and capture sound with some level of quality. That is subject to testing, often in anechoic chambers with precise instruments for measuring sound across the audible spectrum of frequencies.

Systems also tend to produce sounds, especially the noise of spinning hard disks, CD-ROMs, floppies, and other drives. Cooling fans are generally not silent, either. Keyboards, mice, and other mechanical parts can make noise as they move. Sometimes, warning noises are irritating or disruptive. For example, my current laptop computer emits a very loud, repetitive tone when the battery gets low, which has frequently disturbed fellow passengers on airplanes. There is no way to customize the volume or type of warning tone emitted. I don't think anyone tested for this particular problem.

The best systems will have limits on how much noise they can produce, and these systems should be tested against these limits. Testing should take into account any factor that affects the noise a system makes. For example, to save power, some laptop computers, rather than switching on a fan to cool a CPU, will downshift the processor speed when operating on battery power. An acoustics test run on a laptop not connected to AC power will fail to detect a noisy fan.