Its adjustable certainly, but still strong

I ordered it for my 3 months kitten, it is therefore a Russian Blue breed a particularly sensitive to noise.
There are certainly three sound levels, but the lowest is fairly noisy, and not frighten your pet. If your pet is also sensitive I suggest you wrap it in a towel when you use it to mitigate the click. Do not you worry, dogs and cats (without health problems) have sharp ears.
I think these sound levels are rather made to suit different size animals (you can click train a horse) or to operate at long distances for example if you teach your dog to fetch a toy. So make sure that the sound is not too loud when you are close and not too close Click ears.

The manual is a good addition for people just starting out. The bottom line in the click training is:
- The timing of the click, which must be precisely at the desired action and not even a half-second later
- Click = Treat: never forget, never reward after a click, even if you click by mistake

Final tips: do not talk, do not praise, choose a really attractive reward to maximize your pet's attention during the sessions, and take short sessions.