Gap irregularity effects in tape recording
J. Mallinson · IEEE Transactions on Magnetics · 1969
In all practical heads the gap deviates from straightness. Such irregularities reduce the output voltage. Assuming that a Gaussian distribution, of variance σ, describes the irregularities, the loss in output is shown to be(13 \sigma/\lambda)^{2}dB. Inordinate losses are avoided if the variance in each head be less than 0.1λ.