Tim Cook, CEO of Apple, attends the annual Allen and Co. Sun Valley media conference in Sun Valley, Idaho, U.S., July 10, 2019.

The sound of rain. Crunching leaves. Someone whispering in your ear.

These are all common themes for what are known as autonomous sensory meridian response (ASMR) videos.

ASMR is a big trend on YouTube, with some channels boasting over 2 million subscribers. Fans of the videos say the soft sounds give them "tingling" sensations and help them relax.

Apple posted four ASMR videos to its YouTube page on Wednesday. The videos, ranging in length from about six minutes to 11 minutes, are advertisements as part of Apple's "shot on iPhone" campaign.

The message? All you need to make ASMR videos is an iPhone, though the videos tell viewers that "additional software and professional hardware" was used.

According to Apple's YouTube description, the videos were shot by Anson Fogel, a director who's previously made other Apple advertisements. The four videos are described as "Season 1," suggesting that Apple might choose to release more ASMR videos.

Apple has a reputation for creative advertising, and has posted several lengthy videos on YouTube in the past, including a short clip by director Spike Jonze last year that won awards.

Check out the videos: