I'm wondering how to make a slo motion sound effect when speed ramping footage. Here an example here: https://youtu.be/gfF2rdrwt2g?t=34

Most of the time I have just cut the audio track where I put key frames in for speed, the used the rate stretch tool on the audio track to slow it down.

I really want to learn how to ramp the audio so you get that cool slo mo sound effect.

Can anybody help with this?