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.