https://en.wikipedia.org/wiki/Social_groomingASMR tingles are the vestige of the primate social grooming instinct. Not all humans experience it, because our social grooming instinct is much weaker than primates. ASMR tingles are a pleasant rippling or tingling sensation across that goes in waves across your neck and scalp, and the sensation encourages you to be calm and stay still (in primates, the staying still bit ensures they don't interrupt the grooming).
Anything that could be related to social grooming can be a trigger, whether it's the literal brushing sound, the experience of being closely inspected, the implication of literally grooming you by cleaning out your ears, seeing someone perform a task methodically and quietly, etc etc.
Content that induces ASMR may serve multiple purposes; the format lends itself to providing intimacy and to providing sexual arousal, so those are common in ASMR and ASMR-adjacent content.
For people who don't experience the tingles, it can be easy to see the other close-by motivations of intimacy / sexual stimulation, and think that's all ASMR is about. As a counterpoint I like to present the original ASMR video, where awareness of this phenomenon first began to coalesce into the beginnings of the ASMR community:
https://www.youtube.com/watch?v=xrKbOF3vHo8It's a middle-aged male doctor giving a brief medical exam to a middle-aged former hockey player, absolutely nothing about it is sexual or intimate in any way. But remember the triggers I listed before, this hits lots of them: methodical task, experience of close examination, and even some brushing sounds from fabric against the mic. It has 25 million views now, but it only had 10,000 views when I first stumbled across it and got hooked on the tingles, and saw someone saying "Is anyone else getting scalp tingles from this?" in the comments.
Hope this helps, OP
t. oldfag in the asmr community