from datasets import load_dataset, Audio
dataset = load_dataset("facebook/voxpopuli", "nl", split="train")
len(dataset)
20968

20968 examples should be sufficient for fine-tuning. SpeechT5 expects audio data to have a sampling rate of 16 kHz, so 
make sure the examples in the dataset meet this requirement:
py
dataset = dataset.cast_column("audio", Audio(sampling_rate=16000))
Preprocess the data
Let's begin by defining the model checkpoint to use and loading the appropriate processor: