Several observers have reported the peculiar phenomenon that passage of an alternating current through a semiconductor produces noise near zero frequency with 1/f spectrum, as well as producing 1/ Delta f sidebands on either side of the excitation frequency. Bull and Bozic (Br. J. Appl. Phys., vol.18, p.883 (1967)) reported the generation of white noise at low frequency. Re-examination of their data, taking account of the analysis of Lorteije and Hoppenbrouwers (Phillips Res. Rep., vol.26, p.29 (1971)), suggests that their experiment also produced 1/f noise plus 1/ Delta f noise, rather than white noise at low frequency.