Tones rising from noise. A study of the detactability of ramped tones masked by noise.

Abstract

Fan noise from personal computers is, for many, a constant presence. It would be a beneficial development if they were less obtrusive and hardly noticeable. With this in mind, a psychoacoustic listening test was conducted with the goal of determining the limen of detection for a tone ramping like a computer fan increasing its speed to full power. The results of this test indicate that, in the tested octave, a change rate of ΔLp / Δt ≈ 0.17 dB/s and Δf / Δt ≈ 2.9 Hz/s and lower are detected at approximately the same point in the ramp. An additional test was conducted as an investigation into the threshold of audibility for hearing the tonal component of a fan in its normal running mode where the only background noise is the computer. This threshold was found to be Lp ≈ 1.5 dB louder than the background noise.