I used the NIOSH sound measurement app to measure the comparative volumes of 11 Bluetooth wallet trackers.
I used my iPhone 8 to measure the volume at a the distance of one 1 inch away and again at 1 meter. In each case, I pointed the bottom microphone directly at each tracker and recorded the maximum sound level during a 10 second period.
Keep in mind that the loudness of the ringer volume of your tracker when it’s inside your wallet or between the sofa cushions will be substantially reduced.
Additionally, the frequency of the sound and the type of sound is different with each one of these trackers. Depending on the sensitivity of your ears, some of these trackers will be seem louder than others, even if the stated sound level measurements are similar.