Two experiments were conducted. The first was a control condition and used the probe signal method similar to Greenberg and Larkin (1968) to see if a filter-like attentional mechanism was acting when listeners were presented with pure tone stimuli in the presence of background noise. The second experiment also used the probe signal method of Greenberg and Larkin (1968) to investigate the extent to which listeners direct their attention to a particular fundamental frequency (f0) when detecting complex tones masked by noise. Twenty adult listeners ranging from 23 years to 54 years with a median age of 28 years participated in both experiments. Of the 20 listeners, 8 were male and 14 were female. Both experiments used a Two Interval Forced Choice (2IFC) procedure. There were two types of trials, the target signal trial and the probe signal trial. The target frequency was presented on 71% of trials, and the probe frequencies on the remaining 29%. The results of Experiment 1 were similar to those obtained in Greenberg and Larkin’s (1968) pioneering study. The 1000 Hz target tone was detected at a significantly higher proportion than probe signals differing in frequency (p < 0.05). Detection scores were observed to be higher when probe signals had a frequency close to the 1000 Hz signal compared to when they had a frequency positioned further from the 1000 Hz target tone. Experiment 2 using complex target tones with f0 of 115 Hz (part 1) and 220 Hz (part 2) revealed a similar pattern to Experiment 1. Listener’s detection scores decreased the further the f0 of probe tones were positioned from the f0 of the target tone, revealing the shape of a band-pass filter. This pattern is consistent with the presence of an auditory attentional filter in the f0 domain for complex tones