Here's the manual: https://www.scirra.com/manual/109/audio
A volume of 0 dB is original volume, and below 0 dB attenuates the sound. Note amplification is not supported. For example, entering a value of -10 plays the audio back 10 dB quieter (about half as loud). Prefer setting the intended volume in the Play action; even if followed immediately by a Set volume action, some platforms will momentarily play the audio at the volume given in the Play action.
I told my dentist I had trouble with my teeth and asked her to fix it without looking in my mouth..