Audibility of temporal smearing and time misalignment of acoustic signals

Misalignment in timing between drivers in a speaker system and temporal smearing of signals in components and cables has long been alleged to cause degradation of fidelity in audio reproduction. It has also been noted that listeners prefer higher sampling rates (e.g., 96 kHz) than the 44.1 kHz of the digital compact disk, even though the 22 kHz Nyquist frequency of the latter already exceeds the nominal single-tone high-frequency hearing limit fmax ~18 kHz. These qualitative and anecdotal observations point to the possibility that human hearing may be sensitive to temporal errors, τ, that are shorter than the reciprocal of the limiting angular frequency [2 π fmax]-1≈ 9µs, thus necessitating bandwidths in audio equipment that are much higher than fmax in order to preserve fidelity. The blind trials of the present work provide quantitative proof of this by assessing the discernability of time misalignment between signals from spatially displaced speakers. The experiment found a displacement threshold of d ≈ 2mm corresponding to a delay discrimination of τ ≈ 9µs.