Create a new image in Acorn, File ▸ New. The dimensions used here are 1200 x 1200 pixels with a transparent background. Go to Filter ▸ Generator ▸ Render Clouds. The settings used can be seen below.
Click on the ‘+’ button at the top of the layers window. Choose Misc ▸ Clamp. Click on the + button again and choose Generator ▸ Random Noise. Set the blending mode of the filter to ‘Soft Light’.
Click on the + button in the filter inspector and choose Distortion Effect ▸ Glass Distortion. Drag and drop an image of frosted glass into the texture window of the filter. Many images of frosted glass can be found online.
Type out your text with a white fill and no stroke. Set the blending mode of your text layer to ‘Mask’.
Play around with the settings of the filters. In the final image below the random noise filter visibility was turned off.
Thank you to RetroSupply for the idea.