Jayisgrateful I cover this in the usage guide. But essentially, you want to be as close to the speaker as possible. That's why I recommend a phone. I'll copy and paste from the usage guide for your convience:
METHOD 1 (weak but effortless)
Set phone's volume to highest
Stick the speaker to your body
Play the sound 1 or more times, how much you feel necessary.
METHOD 2 (stronger but effortful)
Shake a plastic water bottle vigorously for 10 seconds
Set phone's volume to highest
Stick your phone's speaker as close as you can to the plastic bottle, bending it a little.
Play the sound 1 or more times, how much you feel necessary
Wizards have been to this domain before