Try listening to the Interaural Level Differences (ILDs) below for 500 Hz tones and 4000 Hz tones. Which frequency do you find easier to locate using ILDs?
Low-Frequency Tones (500 Hz)
High-Frequency Tones (4000 Hz)
Once you have decided which is easier to locate, return to the worksheet (section 4.1) to answer the relevant questions.
UCL Ear Institute 