all conv layers are batch independent
nn.Conv1d(1, 32, 16) means 1 input channel, 32 output channels, kernel size = 16. Thus it expects tensor with shape (X, 1, (at least 16)), where X is some amount of elements (batch with size at least 1), 1 is number of input channels, (at least 16) is your input data per channel, should be equal to or larger than kernel size.
You are passing 2 elements with shape (2048), .unsqueeze(1) this tensor at dim=1 to convert your input data to shape (2, 1, 2048)
PS. Kernel size 16 is rather large