Example of 1D ConvNet filter
Images are two dimensional signals. The use of Conv1D is for one dimensional signals like voice and sound. CNNs are good for these signals too because of taking care of local input patterns. Definitely there are standard one dimensional filters which are most used in signal processing like high pass filters and low pass filters which are so much popular. In order to show you an example take a look at the following figure which illustrates the convolution of two signals: