DMA should be right regarding 8287Hz.
However to add, the STE DMA is of course 8-bit. You are using Audacity, that doesn't support 8-bit samples. What is your sample bit rate, that is likely your issue, you probably require your samples to be 8-bit at 8287Hz. So if you are using Audacity, you will have to force them to that bit and sample rate.
On a Mac or PC, you could do this by:
Open up your samples in Apple QuickTime Movie Player.
Select Export... from the File menu in QuickTime Player. Under the Export dropdown menu, select sound to wave. Click on the Options... button. Set the dialog box to the following settings:
Format: PCM; Channels: Mono; Rate: 8.287 KHz; Quality: Best; Sample Size: 8 bits.
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